Heat therapy , also called thermotherapy , is the application of
heat to the body for pain relief and health. It can take the form
of a hot cloth, hot water, ultrasound , heating pad , hydrocollator
packs, whirlpool baths, cordless FIR heat therapy wrap, and many
others. It can be beneficial to those with arthritis and stiff
muscles and injuries to the deep tissue of the skin. Heat may be an
effective self-care treatment for conditions like rheumatoid
arthritis . [ 1 ]
Heat therapy is most commonly used for rehabilitation purposes. The
therapeutic effects of heat include increasing the extensibility of
collagen tissues; decreasing joint stiffness; reducing pain;
relieving muscle spasms; reducing inflammation, edema , and aids in
the post acute phase of healing; and increasing blood flow. The
increased blood flow to the affected area provides proteins,
nutrients, and oxygen for better healing. [ 2 ]
Contents
1 History
2 Application
3 Mechanism of action
4 In plants
5 See also
6 References
//
History
Heat has been used for therapeutic purposes for thousands of years.
Many ancient civilizations worshipped figures of the sun, such as
the Egyptians , who worshipped the sun god Ra .
Application
Moist heat is more effective at warming tissues than dry heat
because water transfers heat more quickly than air. This results in
the perception that the tissue is heated more deeply, which
increases the effect on muscles, joints, and soft tissue. Heat is
typically applied by placing very warm, wet towels on the relevant
body part.
The newest breed of heat therapy device such as "FIR Cordless Heat
Therapy" such as the one developed by +Venture Heat combines the
carbon fiber heater with cordless rechargeable Lithium battery and
built into the specific body wrap (ie. shoulder wrap or back wrap)
for a targeted heat therapy can be use as an alternative to the
chemical or plugged-in heating pads.
Mechanism of action
Heat therapy creates higher superficial tissue temperatures, which
aids the healing process in some conditions. Heat applied
superficially to the skin directly increases the temperature of the
skin and the tissue immediately underneath the skin. Muscle
temperature increases through a reflexive effect on circulation and
through conduction.
Another use is the treatment of infection and cancers by the use of
heat. Cancer cells and many bacteria have poor mechanisms for
adapting to and resisting the physiological stresses of heat, and
are more vulnerable to heat-induced death than normal cells.
In plants
Thermotherapy may also be used in vine propagation to get rid of
viroids (particles smaller than viruses) which may affect the new
vine.
A water ionizer is an appliance that ionizes water . Ionized water
is purported to be beneficial to human health and marketed with
claims that it is an antioxidant which can slow aging and prevent
disease. [ 1 ] Others note that such claims contradict basic laws
of chemistry and physiology. [ 2 ]
Contents
1 Ionization
2 Uses
3 See also
4 References
5 External links
//
Ionization
Main article: Electrolysis of water
A water ionizer separates water into alkaline and acid fractions
using a process known as electrolysis . [ 3 ] It does this by
exploiting the electric charge of the calcium and magnesium ions
present in nearly all sources of drinking water. When a source of
water lacks mineral ions, such as distilled water , or has been
filtered by reverse osmosis , water ionization has no effect.
Uses
Some research suggests that alkaline reduced water may be useful in
scavenging free radicals in the laboratory setting. [ 4 ] Tests on
in vitro lymphocytes suggest that reduced water can prevent
hydrogen peroxide -induced damage to DNA , RNA and certain proteins
. [ 5 ] However, drinking ionized water would not be expected to
alter the body's pH , and there is no evidence of any claims made
by manufacturers that drinking ionized water will have a noticeable
effect on the body. [ 2 ]
Electrolyzed water has been used by the food industry to sanitize
food products; though effective in bacterial solutions, it was
found less useful when sanitizing utensils, surfaces and food
products. [ 6 ] [ 7 ] Acidic electrolyzed water (pH 2.3–2.6)
may have use as a seed surface disinfectant or contact bactericide
. [ 8 ]
Medical equipment is designed to aid in the diagnosis, monitoring
or treatment of medical conditions. These devices are usually
designed with rigorous safety standards . The medical equipment is
included in the category Medical technology .
There are several basic types:
Diagnostic equipment includes medical imaging machines, used to aid
in diagnosis. Examples are ultrasound and MRI machines, PET and CT
scanners, and x-ray machines .
Therapeutic equipment includes infusion pumps , medical lasers and
LASIK surgical machines.
Life support equipment is used maintain a patient's bodily
function. These include medical ventilators , anaesthetic machines
, heart-lung machines , ECMO , and dialysis machines .
Medical monitors allow medical staff to measure a patient's medical
state. Monitors may measure patient vital signs and other
parameters including ECG , EEG , blood pressure , and dissolved
gases in the blood.
Medical laboratory equipment automates or helps analyze blood ,
urine and genes .
Diagnostic Medical Equipment may also be used in the home for
certain purposes, e.g. for the control of diabetes mellitus
A biomedical equipment technician ( BMET ) is a vital component of
the healthcare delivery system. Employed primarily by hospitals,
BMETs are the people responsible for maintaining a facility's
medical equipment.
Inventions
1895, X-ray , by Wilhelm Röntgen
1903, electrocardiograph , by Willem Einthoven
1956, endoscope , by Basil Hirschowitz
1958, ultrasound scan , by Ian Donald
1973, CT (CAT) scan , by Godfrey Hounsfield and Allan Cormack
1982, artificial heart , by Robert Jarvik
Source
Running Press Cyclopedia, second edition.
Notable medical equipment companies
Boston Scientific
Beckman Coulter
Dräger
GE Healthcare
Getinge Group
Heine Optotechnik
Johnson & Johnson
MAQUET
Medtronic
Mindray
Philips
St. Jude Medical
Siemens AG
See also
Medical technology
Medical device
Durable medical equipment
Eucomed
Home medical equipment
Surgical instruments
Medical test
Medical grade silicone
Amethyst is a violet variety of quartz often used in jewelry . The
name comes from the Ancient Greek ἀ a- ("not") and
μέθυστος methustos
("intoxicated"), a reference to the belief that the stone protected
its owner from drunkenness ; the ancient Greeks and Romans wore
amethyst and made drinking vessels of it in the belief that it
would prevent intoxication .
Contents
1 Chemistry
2 Composition
3 Hue and tone
4 History
4.1 Mythology
5 Geographic distribution
6 Value
7 See also
8 Notes
9 References
10 External links
//
Chemistry
Amethyst is the violet variety of quartz ; its chemical formula is
SiO 2 .
In the 20th century, the color of amethyst was attributed to the
presence of manganese . However, since it is capable of being
greatly altered and even discharged by heat, the color was believed
by some authorities to be from an organic source. Ferric
thiocyanate was suggested, and sulfur was said to have been
detected in the mineral.
More recent work has shown that amethyst's coloration is due to
ferric iron impurities. [ 1 ] Further study has shown a complex
interplay of iron and aluminium is responsible for the color. [ 2
]
On exposure to heat, amethyst generally becomes yellow , and much
of the citrine , cairngorm , or yellow quartz of jewelry is said to
be merely "burnt amethyst". Veins of amethystine quartz are apt to
lose their color on the exposed outcrop [ citation needed ] .
Synthetic amethyst is made to imitate the best quality amethyst.
Its chemical and physical properties are so similar to that of
natural amethyst that it can not be differentiated with absolute
certainty without advanced gemological testing (which is often
cost-prohibitive). There is one test based on "Brazil law twinning"
(a form of quartz twinning where right and left hand quartz
structures are combined in a single crystal [ 3 ] ) which can be
used to identify synthetic amethyst rather easily. In theory
however it is possible to create this material synthetically as
well, but this type is not available in large quantities in the
market. [ 4 ]
Composition
Amethyst is composed of an irregular superposition of alternate
lamellae of right-handed and left-handed quartz. It has been shown
that this structure may be due to mechanical stresses.
Because it has a hardness of seven on the Mohs scale , amethyst is
suitable for use in jewelry.
Hue and tone
Amethyst occurs in primary hues from a light pinkish violet to a
deep purple. Amethyst may exhibit one or both secondary hues, red
and blue. The ideal grade is called "Deep Siberian" and has a
primary purple hue of around 75–80 percent, 15–20
percent blue and (depending on the light source) red secondary
hues. [ 4 ]
Cut Amethyst
The inside of an Amethyst Geode
History
Roman intaglio engraved gem of Caracalla in amethyst, once in the
Treasury of Sainte-Chapelle .
Amethyst was used as a gemstone by the ancient Egyptians and was
largely employed in antiquity for intaglio engraved gems . [ 5
]
The Greeks believed amethyst gems could prevent intoxication ,
while medieval European soldiers wore amethyst amulets as
protection in battle. [ 6 ] Beads of amethyst were found in
Anglo-Saxon graves in England . [ citation needed ]
A huge geode , or "amethyst-grotto", from near Santa Cruz in
southern Brazil was exhibited at the Düsseldorf, Germany
Exhibition of 1902.
Amethyst is the traditional birthstone for February.
Mythology
The Greek word "amethystos" may be translated as "not drunken",
from Greek a- , not + methustos , intoxicated [ 7 ] . Amethyst was
considered to be a strong antidote against drunkenness, which is
why wine goblets were often carved from it. In Greek mythology,
Dionysus , the god of intoxication,and wine, was pursuing a maiden
named Amethystos, who refused his affections. Amethystos prayed to
the gods to remain chaste, which the goddess Artemis granted and
transformed her into a white stone. Humbled by Amethystos's desire
to remain chaste, Dionysus poured wine over the stone as an
offering, dyeing the crystals purple.
Variations of the story include that Dionysus had been insulted by
a mortal and swore to slay the next mortal who crossed his path,
creating fierce tigers to carry out his wrath. The mortal turned
out to be a beautiful young woman, Amethystos, who was on her way
to pay tribute to Artemis(the hunter goddess). Her life is spared
by Artemis, who transformed the maiden into a statue of pure
crystalline quartz to protect her from the brutal claws. Dionysus
wept tears of wine in remorse for his action at the sight of the
beautiful statue. The god's tears then stained the quartz purple. [
8 ] Another variation involves the titan Rhea presenting Dionysus
with the amethyst stone to preserve the wine-drinker's sanity. [ 9
]
Geographic distribution
Amethyst is produced in abundance from the state of Minas Gerais in
Brazil where it occurs in large geodes within volcanic rocks . It
is also found and mined in South Korea . The largest opencast
amethyst vein in the world is in Maissau, Lower Austria. Many of
the hollow agates of Brazil and Uruguay contain a crop of amethyst
crystals in the interior. Much fine amethyst comes from Russia ,
especially from near Mursinka in the Ekaterinburg district, where
it occurs in drusy cavities in granitic rocks. Many localities in
India yield amethyst. One of the largest global amethyst producers
is Zambia with an annual production of about 1,000 t.
Amethyst cluster
Amethyst occurs at many localities in the United States . Among
these may be mentioned: the Mazatzal Mountain region in Gila and
Maricopa Counties , Arizona ; Amethyst Mountain, Texas ;
Yellowstone National Park ; Delaware County, Pennsylvania ; Haywood
County, North Carolina ; Deer Hill and Stow, Maine and in the Lake
Superior region. Amethyst is relatively common in Ontario , and in
various locations throughout Nova Scotia . The largest amethyst
mine in North America is located in Thunder Bay , Ontario. [ 10 ]
.
Value
Up to 18th century amethyst was included in the cardinal, or most
valuable, gemstones (along with diamond , sapphire , ruby , and
emerald ). However since the discovery of extensive deposits in
locations such as Brazil it has lost most of its value.
Collectors look for depth of color, possibly with red flashes if
cut conventionally. [ 11 ] . The highest grade amethyst (called
"Deep Russian") is exceptionally rare and therefore its value is
dependent on the demand of collectors when one is found. It is
however still orders of magnitude lower than the highest grade
sapphires or rubies ( Padparadscha sapphire or "pigeon's blood"
ruby). [ 4 ]
Medical equipment is designed to aid in the diagnosis, monitoring
or treatment of medical conditions. These devices are usually
designed with rigorous safety standards . The medical equipment is
included in the category Medical technology .
There are several basic types:
Diagnostic equipment includes medical imaging machines, used to aid
in diagnosis. Examples are ultrasound and MRI machines, PET and CT
scanners, and x-ray machines .
Therapeutic equipment includes infusion pumps , medical lasers and
LASIK surgical machines.
Life support equipment is used maintain a patient's bodily
function. These include medical ventilators , anaesthetic machines
, heart-lung machines , ECMO , and dialysis machines .
Medical monitors allow medical staff to measure a patient's medical
state. Monitors may measure patient vital signs and other
parameters including ECG , EEG , blood pressure , and dissolved
gases in the blood.
Medical laboratory equipment automates or helps analyze blood ,
urine and genes .
Diagnostic Medical Equipment may also be used in the home for
certain purposes, e.g. for the control of diabetes mellitus
A biomedical equipment technician ( BMET ) is a vital component of
the healthcare delivery system. Employed primarily by hospitals,
BMETs are the people responsible for maintaining a facility's
medical equipment.
Inventions
1895, X-ray , by Wilhelm Röntgen
1903, electrocardiograph , by Willem Einthoven
1956, endoscope , by Basil Hirschowitz
1958, ultrasound scan , by Ian Donald
1973, CT (CAT) scan , by Godfrey Hounsfield and Allan Cormack
1982, artificial heart , by Robert Jarvik
Source
Running Press Cyclopedia, second edition.
Notable medical equipment companies
Boston Scientific
Beckman Coulter
Dräger
GE Healthcare
Getinge Group
Heine Optotechnik
Johnson & Johnson
MAQUET
Medtronic
Mindray
Philips
St. Jude Medical
Siemens AG
See also
Medical technology
Medical device
Durable medical equipment
Eucomed
Home medical equipment
Surgical instruments
Medical test
Medical grade silicone
Amethyst healing is an art and
practice, done on a metaphysical level that has been re-discovered
because of the power of the earth's energies that have been
absorbed by these sacred objects. In turn, they inherit vital
healing powers for many types of ailments. Amethyst has come to be
known as a power crystal with prolific healing powers that can be
characterized as purifying, pacifying and transitional .
Amethyst has the ability to transform
lower energies into higher and acts as a healer at all levels of
mind, body, and spirit. The healing powers of Amethyst date as far
back as the Greeks who believed that Amethyst protected a person
from the intoxicating effects of alcohol.
The world's best source of Amethyst
comes from Korea. Known for its power to detoxify the body from
alcohol and other harmful elements, Amethyst also produces Far
Infrared Rays. These rays revitalize the biological function of
your cells to: increase blood circulation, promote perspiration,
relieve neuralgia, backaches, and arthritis, and eliminate toxins .
The far Infrared rays are good for relaxation, perform an
anti-bacterial function and purify the air . Amethyst amplifies Far
Infrared Light 200X more powerfully than FIR by itself.
There are many physical uses which
the healing powers of Amethyst are a remedy. As an elixir, Amethyst
can be used to treat tooth aches, skeletal discomforts, posture and
other bone and joint-related sickness (such as arthritis). Amethyst
also cures problems within the stomach and digestive tract, heart
and hearing disorders . Amethyst has been known to treat various
types of blood disease, and balancing blood sugar .
As a healing stone or crystal
Amethyst is used to treat and heal problems involving the central
nervous system, and is a treatment for both convulsions and
neuralgia, and contains sobering and calming qualities . This stone
is commonly associated with peace. Amethyst soothes those who have
engaged in constant rigorous mental activity. Amethyst has been
deemed as "natures tranqualizer" by many healers because of its
effectiveness in relaxing not only the mind, but also the nervous
system. Amethyst is also known for protecting the mind from psychic
attacks , and transforming negative energy into that of positive
and tranquil tenacity. Amethyst is
identified as a crystal that functions favorably in clearing
certain types of blockage, and in aligning the chakras . By
transforming energies on all levels, amethyst also has the ability
to balance and stabalize energies located within certain areas.
Amethyst is related to and found to heal and align ailments.
Amethyst healing is an art and
practice, done on a metaphysical level that has been re-discovered
because of the power of the earth's energies that have been
absorbed by these sacred objects. In turn, they inherit vital
healing powers for many types of ailments. Amethyst has come to be
known as a power crystal with prolific healing powers that can be
characterized as purifying, pacifying and transitional .
Amethyst has the ability to transform
lower energies into higher and acts as a healer at all levels of
mind, body, and spirit. The healing powers of Amethyst date as far
back as the Greeks who believed that Amethyst protected a person
from the intoxicating effects of alcohol.
The world's best source of Amethyst
comes from Korea. Known for its power to detoxify the body from
alcohol and other harmful elements, Amethyst also produces Far
Infrared Rays. These rays revitalize the biological function of
your cells to: increase blood circulation, promote perspiration,
relieve neuralgia, backaches, and arthritis, and eliminate toxins .
The far Infrared rays are good for relaxation, perform an
anti-bacterial function and purify the air . Amethyst amplifies Far
Infrared Light 200X more powerfully than FIR by itself.
There are many physical uses which
the healing powers of Amethyst are a remedy. As an elixir, Amethyst
can be used to treat tooth aches, skeletal discomforts, posture and
other bone and joint-related sickness (such as arthritis). Amethyst
also cures problems within the stomach and digestive tract, heart
and hearing disorders . Amethyst has been known to treat various
types of blood disease, and balancing blood sugar .
As a healing stone or crystal
Amethyst is used to treat and heal problems involving the central
nervous system, and is a treatment for both convulsions and
neuralgia, and contains sobering and calming qualities . This stone
is commonly associated with peace. Amethyst soothes those who have
engaged in constant rigorous mental activity. Amethyst has been
deemed as "natures tranqualizer" by many healers because of its
effectiveness in relaxing not only the mind, but also the nervous
system. Amethyst is also known for protecting the mind from psychic
attacks , and transforming negative energy into that of positive
and tranquil tenacity. Amethyst is
identified as a crystal that functions favorably in clearing
certain types of blockage, and in aligning the chakras . By
transforming energies on all levels, amethyst also has the ability
to balance and stabalize energies located within certain areas.
Amethyst is related to and found to heal and align ailments.
A water supply system or water supply network is a system of
engineered hydrologic and hydraulic components which provide water
supply . A water supply system typically includes:
The watershed or geographic area that collects the water (see water
purification - sources of drinking water );
A raw (untreated) water collection point (above or below ground)
where the water accumulates, such as a lake , a river , or
groundwater from an underground aquifer . Untreated drinking water
(usually water being transferred to the water purification
facilities) may be transferred using uncovered ground-level
aqueducts , covered tunnels or underground water pipes .
Water purification facilities. Treated water is transferred using
water pipes (usually underground).
Water storage facilities such as reservoirs , water tanks , or
watertowers . Smaller water systems may store the water in cisterns
or pressure vessels . (Tall buildings may also need to store water
locally in pressure vessels in order for the water to reach the
upper floors.)
Additional water pressurizing components such as pumping stations
may need to be situated at the outlet of underground or above
ground reservoirs or cisterns (if gravity flow is unfeasible)
A pipe network for distribution of water to the consumers (which
may be private houses or industrial, commercial or institution
establishments) and other usage points (such as fire hydrants )
Connections to the sewers (underground pipes, or aboveground
ditches in some developing countries) are generally found
downstream of the water consumers, but the sewer system is
considered to be a separate system, rather than part of the water
supply system
Contents
1 Water abstraction and raw water transfer
2 Water treatment
3 Water distribution network
4 Topologies of water distribution networks
5 Water network maintenance
6 Note on connections to the sewer system
7 See also
8 References
9 External links
//
Water abstraction and raw water transfer
Main article: Water abstraction
Raw water (untreated) is collected from a surface water source
(such as an intake on a lake or a river ) or from a groundwater
source (such as a water well drawing from an underground aquifer )
within the watershed that provides the water resource .
Shallow dams and reservoirs are susceptible to outbreaks of toxic
algae , especially if the water is warmed by a hot sun. The
bacteria grow from stormwater runoff carrying fertilizer into the
river where it acts as a nutrient for the algae. Such outbreaks
render the water unfit for human consumption.
The raw water is transferred to the water purification facilities
using uncovered aqueducts , covered tunnels or underground water
pipes .
Water treatment
Main article: Water treatment
Virtually all large systems must treat the water; a fact that is
tightly regulated by global, state and federal agencies, such as
the World Health Organization (WHO) or the United States
Environmental Protection Agency (EPA). Water treatment must occur
before the product reaches the consumer and afterwards (when it is
discharged again). Water purification usually occurs close to the
final delivery points to reduce pumping costs and the chances of
the water becoming contaminated after treatment.
Traditional surface water treatment plants generally consists of
three steps: clarification, filtration and disinfection.
Clarification refers to the separation of particles (dirt, organic
matter, etc.) from the water stream. Chemical addition (i.e. alum,
ferric chloride) destabilizes the particle charges and prepares
them for clarification either by settling or floating out of the
water stream. Sand, anthracite or activated carbon filters refine
the water stream, removing smaller particulate matter. While other
methods of disinfection exist, the preferred method is via chlorine
addition. Chlorine effectively kills bacteria and most viruses and
maintains a residual to protect the water supply through the supply
network.
Water distribution network
The Central Arizona Project Aqueduct transfers untreated water
Most (treated) water distribution happens through underground
pipes
Pressurizing the water is required between the small water reserve
and the end-user
The product, delivered to the point of consumption, is called fresh
water if it receives little or no treatment, or drinking water if
the treatment achieves the water quality standards required for
human consumption.
Once treated, chlorine is added to the water and it is distributed
by the local supply network. Today, water supply systems are
typically constructed of plastic, ferrous, or concrete circular
pipe. However, other "pipe" shapes and material may be used, such
as square or rectangular concrete boxes, arched brick pipe, or wood
. Near the end point, the network of pipes through which the water
is delivered is often referred to as the water mains .
The energy that the system needs to deliver the water is called
pressure . That energy is transferred to the water, therefore
becoming water pressure , in a number of ways: by a pump , by
gravity feed from a water source (such as a water tower ) at a
higher elevation, or by compressed air. [ 1 ]
The water is often transferred from a water reserve such as a large
communal reservoir before being transported to a more pressurised
reserve as a watertower.
In small domestic systems, the water may be pressurised by a
pressure vessel or even by an underground cistern (the latter
however does need additional pressurizing). This eliminates the
need of a watertower or any other heightened water reserve to
supply the water pressure.
These systems are usually owned and maintained by local governments
, such as cities , or other public entities, but are occasionally
operated by a commercial enterprise (see water privatization ).
Water supply networks are part of the master planning of
communities, counties, and municipalities. Their planning and
design requires the expertise of city planners and civil engineers
, who must consider many factors, such as location, current demand,
future growth, leakage, pressure, pipe size, pressure loss, fire
fighting flows, etc. — using pipe network analysis and other
tools. [[Construction]comparable sewage systems, was one of the
great engineering advances that made urbanization possible.
Improvement in the quality of the water has been one of the great
advances in public health .
As water passes through the distribution system, the water quality
can degrade by chemical reactions and biological processes.
Corrosion of metal pipe materials in the distribution system can
cause the release of metals into the water with undesirable
aesthetic and health effects. Release of iron from unlined iron
pipes can result in customer reports of "red water" at the tap .
Release of copper from copper pipes can result in customer reports
of "blue water" and/or a metallic taste. Release of lead can occur
from the solder used to join copper pipe together or from brass
fixtures . Copper and lead levels at the consumer's tap are
regulated to protect consumer health.
Utilities will often adjust the chemistry of the water before
distribution to minimize its corrosiveness. The simplest adjustment
involves control of pH and alkalinity to produce a water that tends
to passivate corrosion by depositing a layer of calcium carbonate .
Corrosion inhibitors are often added to reduce release of metals
into the water. Common corrosion inhibitors added to the water are
phosphates and silicates .
Maintenance of a biologically safe drinking water is another goal
in water distribution. Typically, a chlorine based disinfectant ,
such as sodium hypochlorite or monochloramine is added to the water
as it leaves the treatment plant. Booster stations can be placed
within the distribution system to ensure that all areas of the
distribution system have adequate sustained levels of disinfection
.
Topologies of water distribution networks
Like electric power lines, roads, and microwave radio networks,
water systems may have a loop or branch network topology, or a
combination of both. The piping networks are circular or
rectangular. If any one section of water distribution main fails or
needs repair, that section can be isolated without disrupting all
users on the network.
Most systems are divided into zones. Factors determining the extent
or size of a zone can include hydraulics, telemetry systems,
history, and population density. Sometimes systems are designed for
a specific area then are modified to accommodate development.
Terrain affects hydraulics and some forms of telemetry. While each
zone may operate as a stand-alone system, there is usually some
arrangement to interconnect zones in order to manage equipment
failures or system failures.
Water network maintenance
Water supply networks usually represent the majority of assets of a
water utility. Systematic documentation of maintenance works using
a Computerized Maintenance Management System is a key to a
successful operation of a water utility.
[ edit ] Note on connections to the sewer system
Connections to the sewers are generally found downstream of the
water consumers.
However, a hook-up to the sewerage system is unnecessary if the
sewage is properly treated on-site. In line with the principle of
ecological sanitation , rather than relying on water to transport
feces and urine, compost toilets can be used which eliminate this
extra water pollution (comprising some 30% of the water
requirements).
See also
Water portal
Aqueduct
Domestic water system
Goldfields Water Supply Scheme
Hardy Cross
Hosepipe ban
Hydrology
Infrastructure
Plumbing
Tap water
Water supply in Hong Kong
Water
Water pipes
Water Meters
Automatic meter reading
Backflow prevention device
Fire hydrant
Strainers
Valve
Water tower
Water quality
Water resources
Water supply
The New Age (also referred to as the New Age movement , New Age
spirituality , and Cosmic Humanism ) is a decentralized Western
social and spiritual movement that seeks " Universal Truth " and
the attainment of the highest individual human potential . It
includes aspects of Occultism , astrology , esotericism ,
metaphysics , alternative medicine , music , collectivism ,
sustainability , and nature . New Age spirituality is characterized
by an individual approach to spiritual practices and philosophies,
and the rejection of religious doctrine and dogma .
The New Age movement includes elements of older spiritual and
religious traditions ranging from atheism and monotheism through
classical pantheism , naturalistic pantheism , and panentheism to
polytheism combined with science and Gaia philosophy : particularly
archaeoastronomy , astronomy , ecology , environmentalism , the
Gaia hypothesis , psychology , and physics . New Age practices and
philosophies sometimes draw inspiration from major world religions
: Buddhism , Chinese folk religion , Christianity , Hinduism ,
Islam , Judaism ; with particularly strong influences from East
Asian religions , Gnosticism , Neopaganism , New Thought ,
Spiritualism , Theosophy , Universalism , and Western esotericism .
[ 2 ] Additional terms for the movement include All is One [ 3 ]
and Mind-Body-Spirit . [ 1 ]
The modern New Age movement emerged in a distinct form in the late
1960s and early 1970s, although its roots can be traced back to the
19th and early 20th centuries. It gained momentum in the 1980s and
strengthened with the Harmonic Convergence event in 1987. Diverse
individuals from around the world practice New Age spirituality. [
citation needed ]
Contents
1 Movement
1.1 Origins
1.2 Development
1.3 Postmodern
2 Spirituality
2.1 Philosophy and cosmology
2.2 Religion and science
3 Lifestyle
3.1 Demographics
3.2 Holistic health
3.3 Music
3.4 Sustainable living
4 Reception
4.1 Organized religion
4.2 Integral Theory
4.3 Indigenous peoples of the Americas
5 In popular culture
6 See also
7 Notes
8 References
9 Further reading
10 External links
//
Movement
Origins
See also: List of Neopagan movements , List of new religious
movements , and List of religions and spiritual traditions
The term New Age was used as early as 1809 by William Blake who
described a belief in a spiritual and artistic "New Age" in his
preface to Milton: a Poem .
Some of the New Age movement's constituent elements appeared
initially in 19th century metaphysical movements: Spiritualism ,
Theosophy , and New Thought ; also, alternative medicine movements
chiropractic and naturopathy . [ 1 ] [ 3 ] These movements in turn
have roots in Transcendentalism , Mesmerism , Swedenborgianism ,
and various earlier Western esoteric or occult traditions, such as
the hermetic arts of astrology, magic , alchemy , and Kabbalah .
The term New Age was used in this context in Madame Blavatsky 's
book The Secret Doctrine , published in 1888. [ 4 ]
A weekly journal of Christian liberalism and socialism titled The
New Age was published as early as 1894; [ 5 ] it was sold to a
group of socialist writers headed by Alfred Richard Orage and
Holbrook Jackson in 1907. Other historical personalities were
involved: H. G. Wells , George Bernard Shaw , and William Butler
Yeats ; the magazine became a forum for politics , literature , and
the arts . [ 6 ] [ 7 ] Between 1908 and 1914, it was instrumental
in pioneering the British avant-garde from vorticism to imagism .
After 1914, publisher Orage met P. D. Ouspensky , a follower of G.
I. Gurdjieff , and began correspondence with Harry Houdini ,
becoming less interested in literature and art, with an increased
focus on mysticism and other spiritual topics; the magazine was
sold in 1921. According to Brown University , The New Age "...
helped to shape modernism in literature and the arts from 1907 to
1922." [ 8 ]
Development
Popularisation behind these ideas has roots in the work of early
20th century writers such as D. H. Lawrence and William Butler
Yeats . In the early to middle 1900s, American mystic, theologian,
and founder of the Association for Research and Enlightenment Edgar
Cayce was a seminal influence on what later would be termed the New
Age movement ; he was known in particular for the practice some
refer to as channeling . [ 9 ] Former Theosophist Rudolf Steiner
and his Anthroposophical Movement are a major influence.
Neo-Theosophist Alice Bailey published the book Discipleship in the
New Age (1944), which used the term New Age in reference to the
transition from the Astrological Age of Pisces to Aquarius . While
claims of racial bias in the writings of Rudolf Steiner and Alice
Bailey were made, [ 10 ] Steiner emphasized racial equality as a
principle central to anthroposophical thought and humanity 's
progress. [ 11 ] [ 12 ] Any racial elements from these influences
have not remained part of the Anthroposophical Society as
contemporary adherents of the society have either not adopted or
repudiated these beliefs. [ 13 ] [ 14 ] Another early usage of the
term, was by the American artist, mystic, and philosopher Walter
Russell , who spoke of "... this New Age philosophy of the
spiritual re-awakening of man ..." in his essay "Power Through
Knowledge", which was also published in 1944.
Carl Gustav Jung was an early articulator of the concept of the Age
of Aquarius. [ 15 ] In a letter to H. G. Baynes, dated 12 August
1940, he wrote in a passage concerning the destruction of the
temple of Karnak by an earthquake in 26 BC: "1940 is the year when
we approach the meridian of the first star in Aquarius . It is the
premonitory earthquake of the New Age." [ 16 ]
Postmodern
Main article: Postmodernism
A barrel house—the first dwelling constructed at the Findhorn
Ecovillage
The subculture that would later be called New Age already existed
in the early 1970s, based on and adopting ideas originally present
in the counterculture of the 1960s . The Findhorn Foundation
– an intentional community near Findhorn , Moray , Scotland
founded in 1962 – played an instrumental role during the
early growth period of the New Age movement; it continues to
operate the Findhorn Ecovillage .
Widespread use of the term New Age began in the mid 1970s
(reflected in the title of monthly periodical New Age Journal ) and
probably influenced several thousand small metaphysical book and
gift stores that increasingly defined themselves as "New Age
bookstores". [ 17 ] [ 18 ] As a result of the large-scale
activities surrounding the Harmonic Convergence in the mid 1980s
– the term was further popularised by the American mass media
to describe the alternative spiritual subculture – including
practices such as meditation , channeling, crystal healing , astral
projection , psychic experience, holistic health , simple living ,
and environmentalism; or belief in phenomena such as Earth
mysteries , ancient astronauts , extraterrestrial life ,
unidentified flying objects , crop circles , and reincarnation . A
range of New Age publications appeared by the late 1980s such as
Psychic Guide (later renamed Body, Mind & Spirit ), Yoga
Journal , New Age Voice , New Age Retailer , and NAPRA ReView by
the New Age Publishers and Retailers Alliance.
There were several key moments in raising public awareness of this
subculture: the publication of Linda Goodman 's best selling
astrology books Sun Signs (1968) and Love Signs (1978); Hair: The
American Tribal Love-Rock Musical (1967) with the opening song "
Aquarius " and its memorable line " This is the dawning of the Age
of Aquarius " [emphasis added]; the broadcast of Shirley MacLaine
's television mini-series Out on a Limb (1987); and the Harmonic
Convergence (1987) organized by José Argüelles in
Sedona , Arizona . Also influential were the claims of channelers
Jane Roberts (the Seth Material ) and J. Z. Knight ( Ramtha ), as
well as revealed writings A Course in Miracles (1976) by Helen
Schucman , The Celestine Prophecy (1993) by James Redfield , and
Conversations with God (1995) by Neale Donald Walsch . Relevant
works also include the writings of Eckhart Tolle , Barbara Marx
Hubbard , Marianne Williamson , Deepak Chopra , John Holland , Gary
Zukav , and Wayne Dyer ; also, The Secret (2006) by Rhonda Byrne ,
which was based on the writings of Esther Hicks and Jerry Hicks.
In chemistry , an alkali (from Arabic : Al-Qaly
القلي,
القالي ) is a basic , ionic
salt of an alkali metal or alkaline earth metal element . Alkalis
are best known for being bases that dissolve in water . Bases are
compounds with a pH greater than 7. The adjective alkaline is
commonly used in English as a synonym for base, especially for
soluble bases. This broad use of the term is likely to have come
about because alkalis were the first bases known to obey the
Arrhenius definition of a base and are still among the more common
bases. Since Brønsted-Lowry acid-base theory , the term
alkali in chemistry is normally restricted to those salts
containing alkali and alkaline earth metal elements.
Contents
1 Etymology
2 Common properties
3 Confusion between alkali and base
4 Salts
5 Alkaline soil
6 Lakes
7 References
//
Etymology
The word "alkali" is derived from Arabic al qalīy = the
calcined ashes , referring to the original source of alkaline
substance. Ashes were used in conjunction with animal fat to
produce soap , a process known as saponification .
Common properties
Alkalis are all Arrhenius bases, which form hydroxide ions (OH - )
when dissolved in water. Common properties of alkaline aqueous
solutions include:
Moderately-concentrated solutions (over 10 −3 M) have a pH of
7.1 or greater. This means that they will turn phenolphthalein from
colorless to pink.
Concentrated solutions are caustic (causing chemical burns).
Alkaline solutions are slippery or soapy to the touch, due to the
saponification of the fatty acids on the surface of the skin.
Alkalis are normally water soluble , although some like barium
carbonate are only soluble when reacting with an acidic aqueous
solution.
Acids and alkalis are measured on a pH scale
Alkalis are commonly found in household cleaners and toothpaste
Confusion between alkali and base
The terms "base" and "alkali" are often used interchangeably,
particularly outside of a scientific context, but they do not have
the same meaning. While all alkaline solutions are basic, not all
bases are alkaline. The following are common mistakes:
The phrase "measuring the alkalinity of soil" is incorrect since
the property measured is actually the pH (base property).
Calling bases that are not alkalis, such as ammonia , alkaline
(ammonia is a base but not an alkali).
Also, not all salts formed by alkali metals are alkaline; this
designation applies only to those salts that are basic. And while
most electropositive metal oxides are basic, only the soluble
alkali metal and alkaline earth metal oxides can be correctly
called alkalis.
This definition of an alkali as a basic salt of an alkali metal or
alkaline earth metal is the most common, based on dictionary
definitions [1] [2] , however conflicting definitions of the term
alkali do exist. These include:
Any base that is water-soluble and forms hydroxide ions [3] [4] .
In chemistry, this is more accurately called an Arrhenius base
.
The solution of a base in water [5] . This would be an Arrhenius
base in solution.
Name given by chemists to an important group of subtances, the
behaviour of bases the main alkali are 1,the hydroxides potassium
2,
Salts
Most basic salts are alkali salts, of which common examples
are:
sodium hydroxide (often called "caustic soda")
potassium hydroxide (commonly called "caustic potash")
lye (generic term, for either of the previous two, or even for a
mixture)
calcium carbonate (sometimes called "free lime")
magnesium hydroxide is an example of an atypical alkali since it
has low solubility in water (although the dissolved portion is
considered a strong base due to complete dissociation of its
ions).
Alkaline soil
Soil with a pH value higher than 7.3 is normally referred to as
alkaline. This soil property can occur naturally, due to the
presence of alkali salts. Although some plants do prefer slightly
basic soil (including vegetables like cabbage and fodder like
buffalograss ), most plants prefer a mildly acidic soil (pH between
6.0 and 6.8), and alkaline soils can cause problems.
Lakes
In alkali lakes (a type of salt lake ), evaporation concentrates
the naturally-occurring alkali salts, often forming a crust of
mildly-basic salt across a large area.
Examples of alkali lakes:
Redberry Lake, Saskatchewan , Canada .
Tramping Lake, Saskatchewan , Canada.
Mono lake , California , United States
Summer Lake , Oregon , United States
Alkali Lake, British Columbia and the adjoining reserves of the
Alkali Lake Indian Band are named for a local Alkali Lake, which
got its name from a large patch of alkali on the hillside above the
lake, which is not itself alkali, [ 1 ] although there are many in
the Cariboo district and adjoining regions of the British Columbia
Interior .
A water supply system or water supply network is a system of
engineered hydrologic and hydraulic components which provide water
supply . A water supply system typically includes:
The watershed or geographic area that collects the water (see water
purification - sources of drinking water );
A raw (untreated) water collection point (above or below ground)
where the water accumulates, such as a lake , a river , or
groundwater from an underground aquifer . Untreated drinking water
(usually water being transferred to the water purification
facilities) may be transferred using uncovered ground-level
aqueducts , covered tunnels or underground water pipes .
Water purification facilities. Treated water is transferred using
water pipes (usually underground).
Water storage facilities such as reservoirs , water tanks , or
watertowers . Smaller water systems may store the water in cisterns
or pressure vessels . (Tall buildings may also need to store water
locally in pressure vessels in order for the water to reach the
upper floors.)
Additional water pressurizing components such as pumping stations
may need to be situated at the outlet of underground or above
ground reservoirs or cisterns (if gravity flow is unfeasible)
A pipe network for distribution of water to the consumers (which
may be private houses or industrial, commercial or institution
establishments) and other usage points (such as fire hydrants )
Connections to the sewers (underground pipes, or aboveground
ditches in some developing countries) are generally found
downstream of the water consumers, but the sewer system is
considered to be a separate system, rather than part of the water
supply system
Contents
1 Water abstraction and raw water transfer
2 Water treatment
3 Water distribution network
4 Topologies of water distribution networks
5 Water network maintenance
6 Note on connections to the sewer system
7 See also
8 References
9 External links
//
Water abstraction and raw water transfer
Main article: Water abstraction
Raw water (untreated) is collected from a surface water source
(such as an intake on a lake or a river ) or from a groundwater
source (such as a water well drawing from an underground aquifer )
within the watershed that provides the water resource .
Shallow dams and reservoirs are susceptible to outbreaks of toxic
algae , especially if the water is warmed by a hot sun. The
bacteria grow from stormwater runoff carrying fertilizer into the
river where it acts as a nutrient for the algae. Such outbreaks
render the water unfit for human consumption.
The raw water is transferred to the water purification facilities
using uncovered aqueducts , covered tunnels or underground water
pipes .
Water treatment
Main article: Water treatment
Virtually all large systems must treat the water; a fact that is
tightly regulated by global, state and federal agencies, such as
the World Health Organization (WHO) or the United States
Environmental Protection Agency (EPA). Water treatment must occur
before the product reaches the consumer and afterwards (when it is
discharged again). Water purification usually occurs close to the
final delivery points to reduce pumping costs and the chances of
the water becoming contaminated after treatment.
Traditional surface water treatment plants generally consists of
three steps: clarification, filtration and disinfection.
Clarification refers to the separation of particles (dirt, organic
matter, etc.) from the water stream. Chemical addition (i.e. alum,
ferric chloride) destabilizes the particle charges and prepares
them for clarification either by settling or floating out of the
water stream. Sand, anthracite or activated carbon filters refine
the water stream, removing smaller particulate matter. While other
methods of disinfection exist, the preferred method is via chlorine
addition. Chlorine effectively kills bacteria and most viruses and
maintains a residual to protect the water supply through the supply
network.
Water distribution network
The Central Arizona Project Aqueduct transfers untreated water
Most (treated) water distribution happens through underground
pipes
Pressurizing the water is required between the small water reserve
and the end-user
The product, delivered to the point of consumption, is called fresh
water if it receives little or no treatment, or drinking water if
the treatment achieves the water quality standards required for
human consumption.
Once treated, chlorine is added to the water and it is distributed
by the local supply network. Today, water supply systems are
typically constructed of plastic, ferrous, or concrete circular
pipe. However, other "pipe" shapes and material may be used, such
as square or rectangular concrete boxes, arched brick pipe, or wood
. Near the end point, the network of pipes through which the water
is delivered is often referred to as the water mains .
The energy that the system needs to deliver the water is called
pressure . That energy is transferred to the water, therefore
becoming water pressure , in a number of ways: by a pump , by
gravity feed from a water source (such as a water tower ) at a
higher elevation, or by compressed air. [ 1 ]
The water is often transferred from a water reserve such as a large
communal reservoir before being transported to a more pressurised
reserve as a watertower.
In small domestic systems, the water may be pressurised by a
pressure vessel or even by an underground cistern (the latter
however does need additional pressurizing). This eliminates the
need of a watertower or any other heightened water reserve to
supply the water pressure.
These systems are usually owned and maintained by local governments
, such as cities , or other public entities, but are occasionally
operated by a commercial enterprise (see water privatization ).
Water supply networks are part of the master planning of
communities, counties, and municipalities. Their planning and
design requires the expertise of city planners and civil engineers
, who must consider many factors, such as location, current demand,
future growth, leakage, pressure, pipe size, pressure loss, fire
fighting flows, etc. — using pipe network analysis and other
tools. [[Construction]comparable sewage systems, was one of the
great engineering advances that made urbanization possible.
Improvement in the quality of the water has been one of the great
advances in public health .
As water passes through the distribution system, the water quality
can degrade by chemical reactions and biological processes.
Corrosion of metal pipe materials in the distribution system can
cause the release of metals into the water with undesirable
aesthetic and health effects. Release of iron from unlined iron
pipes can result in customer reports of "red water" at the tap .
Release of copper from copper pipes can result in customer reports
of "blue water" and/or a metallic taste. Release of lead can occur
from the solder used to join copper pipe together or from brass
fixtures . Copper and lead levels at the consumer's tap are
regulated to protect consumer health.
Utilities will often adjust the chemistry of the water before
distribution to minimize its corrosiveness. The simplest adjustment
involves control of pH and alkalinity to produce a water that tends
to passivate corrosion by depositing a layer of calcium carbonate .
Corrosion inhibitors are often added to reduce release of metals
into the water. Common corrosion inhibitors added to the water are
phosphates and silicates .
Maintenance of a biologically safe drinking water is another goal
in water distribution. Typically, a chlorine based disinfectant ,
such as sodium hypochlorite or monochloramine is added to the water
as it leaves the treatment plant. Booster stations can be placed
within the distribution system to ensure that all areas of the
distribution system have adequate sustained levels of disinfection
.
Topologies of water distribution networks
Like electric power lines, roads, and microwave radio networks,
water systems may have a loop or branch network topology, or a
combination of both. The piping networks are circular or
rectangular. If any one section of water distribution main fails or
needs repair, that section can be isolated without disrupting all
users on the network.
Most systems are divided into zones. Factors determining the extent
or size of a zone can include hydraulics, telemetry systems,
history, and population density. Sometimes systems are designed for
a specific area then are modified to accommodate development.
Terrain affects hydraulics and some forms of telemetry. While each
zone may operate as a stand-alone system, there is usually some
arrangement to interconnect zones in order to manage equipment
failures or system failures.
Water network maintenance
Water supply networks usually represent the majority of assets of a
water utility. Systematic documentation of maintenance works using
a Computerized Maintenance Management System is a key to a
successful operation of a water utility.
[ edit ] Note on connections to the sewer system
Connections to the sewers are generally found downstream of the
water consumers.
However, a hook-up to the sewerage system is unnecessary if the
sewage is properly treated on-site. In line with the principle of
ecological sanitation , rather than relying on water to transport
feces and urine, compost toilets can be used which eliminate this
extra water pollution (comprising some 30% of the water
requirements).
See also
Water portal
Aqueduct
Domestic water system
Goldfields Water Supply Scheme
Hardy Cross
Hosepipe ban
Hydrology
Infrastructure
Plumbing
Tap water
Water supply in Hong Kong
Water
Water pipes
Water Meters
Automatic meter reading
Backflow prevention device
Fire hydrant
Strainers
Valve
Water tower
Water quality
Water resources
Water supply
The New Age (also referred to as the New Age movement , New Age
spirituality , and Cosmic Humanism ) is a decentralized Western
social and spiritual movement that seeks " Universal Truth " and
the attainment of the highest individual human potential . It
includes aspects of Occultism , astrology , esotericism ,
metaphysics , alternative medicine , music , collectivism ,
sustainability , and nature . New Age spirituality is characterized
by an individual approach to spiritual practices and philosophies,
and the rejection of religious doctrine and dogma .
The New Age movement includes elements of older spiritual and
religious traditions ranging from atheism and monotheism through
classical pantheism , naturalistic pantheism , and panentheism to
polytheism combined with science and Gaia philosophy : particularly
archaeoastronomy , astronomy , ecology , environmentalism , the
Gaia hypothesis , psychology , and physics . New Age practices and
philosophies sometimes draw inspiration from major world religions
: Buddhism , Chinese folk religion , Christianity , Hinduism ,
Islam , Judaism ; with particularly strong influences from East
Asian religions , Gnosticism , Neopaganism , New Thought ,
Spiritualism , Theosophy , Universalism , and Western esotericism .
[ 2 ] Additional terms for the movement include All is One [ 3 ]
and Mind-Body-Spirit . [ 1 ]
The modern New Age movement emerged in a distinct form in the late
1960s and early 1970s, although its roots can be traced back to the
19th and early 20th centuries. It gained momentum in the 1980s and
strengthened with the Harmonic Convergence event in 1987. Diverse
individuals from around the world practice New Age spirituality. [
citation needed ]
Contents
1 Movement
1.1 Origins
1.2 Development
1.3 Postmodern
2 Spirituality
2.1 Philosophy and cosmology
2.2 Religion and science
3 Lifestyle
3.1 Demographics
3.2 Holistic health
3.3 Music
3.4 Sustainable living
4 Reception
4.1 Organized religion
4.2 Integral Theory
4.3 Indigenous peoples of the Americas
5 In popular culture
6 See also
7 Notes
8 References
9 Further reading
10 External links
//
Movement
Origins
See also: List of Neopagan movements , List of new religious
movements , and List of religions and spiritual traditions
The term New Age was used as early as 1809 by William Blake who
described a belief in a spiritual and artistic "New Age" in his
preface to Milton: a Poem .
Some of the New Age movement's constituent elements appeared
initially in 19th century metaphysical movements: Spiritualism ,
Theosophy , and New Thought ; also, alternative medicine movements
chiropractic and naturopathy . [ 1 ] [ 3 ] These movements in turn
have roots in Transcendentalism , Mesmerism , Swedenborgianism ,
and various earlier Western esoteric or occult traditions, such as
the hermetic arts of astrology, magic , alchemy , and Kabbalah .
The term New Age was used in this context in Madame Blavatsky 's
book The Secret Doctrine , published in 1888. [ 4 ]
A weekly journal of Christian liberalism and socialism titled The
New Age was published as early as 1894; [ 5 ] it was sold to a
group of socialist writers headed by Alfred Richard Orage and
Holbrook Jackson in 1907. Other historical personalities were
involved: H. G. Wells , George Bernard Shaw , and William Butler
Yeats ; the magazine became a forum for politics , literature , and
the arts . [ 6 ] [ 7 ] Between 1908 and 1914, it was instrumental
in pioneering the British avant-garde from vorticism to imagism .
After 1914, publisher Orage met P. D. Ouspensky , a follower of G.
I. Gurdjieff , and began correspondence with Harry Houdini ,
becoming less interested in literature and art, with an increased
focus on mysticism and other spiritual topics; the magazine was
sold in 1921. According to Brown University , The New Age "...
helped to shape modernism in literature and the arts from 1907 to
1922." [ 8 ]
Development
Popularisation behind these ideas has roots in the work of early
20th century writers such as D. H. Lawrence and William Butler
Yeats . In the early to middle 1900s, American mystic, theologian,
and founder of the Association for Research and Enlightenment Edgar
Cayce was a seminal influence on what later would be termed the New
Age movement ; he was known in particular for the practice some
refer to as channeling . [ 9 ] Former Theosophist Rudolf Steiner
and his Anthroposophical Movement are a major influence.
Neo-Theosophist Alice Bailey published the book Discipleship in the
New Age (1944), which used the term New Age in reference to the
transition from the Astrological Age of Pisces to Aquarius . While
claims of racial bias in the writings of Rudolf Steiner and Alice
Bailey were made, [ 10 ] Steiner emphasized racial equality as a
principle central to anthroposophical thought and humanity 's
progress. [ 11 ] [ 12 ] Any racial elements from these influences
have not remained part of the Anthroposophical Society as
contemporary adherents of the society have either not adopted or
repudiated these beliefs. [ 13 ] [ 14 ] Another early usage of the
term, was by the American artist, mystic, and philosopher Walter
Russell , who spoke of "... this New Age philosophy of the
spiritual re-awakening of man ..." in his essay "Power Through
Knowledge", which was also published in 1944.
Carl Gustav Jung was an early articulator of the concept of the Age
of Aquarius. [ 15 ] In a letter to H. G. Baynes, dated 12 August
1940, he wrote in a passage concerning the destruction of the
temple of Karnak by an earthquake in 26 BC: "1940 is the year when
we approach the meridian of the first star in Aquarius . It is the
premonitory earthquake of the New Age." [ 16 ]
Postmodern
Main article: Postmodernism
A barrel house—the first dwelling constructed at the Findhorn
Ecovillage
The subculture that would later be called New Age already existed
in the early 1970s, based on and adopting ideas originally present
in the counterculture of the 1960s . The Findhorn Foundation
– an intentional community near Findhorn , Moray , Scotland
founded in 1962 – played an instrumental role during the
early growth period of the New Age movement; it continues to
operate the Findhorn Ecovillage .
Widespread use of the term New Age began in the mid 1970s
(reflected in the title of monthly periodical New Age Journal ) and
probably influenced several thousand small metaphysical book and
gift stores that increasingly defined themselves as "New Age
bookstores". [ 17 ] [ 18 ] As a result of the large-scale
activities surrounding the Harmonic Convergence in the mid 1980s
– the term was further popularised by the American mass media
to describe the alternative spiritual subculture – including
practices such as meditation , channeling, crystal healing , astral
projection , psychic experience, holistic health , simple living ,
and environmentalism; or belief in phenomena such as Earth
mysteries , ancient astronauts , extraterrestrial life ,
unidentified flying objects , crop circles , and reincarnation . A
range of New Age publications appeared by the late 1980s such as
Psychic Guide (later renamed Body, Mind & Spirit ), Yoga
Journal , New Age Voice , New Age Retailer , and NAPRA ReView by
the New Age Publishers and Retailers Alliance.
There were several key moments in raising public awareness of this
subculture: the publication of Linda Goodman 's best selling
astrology books Sun Signs (1968) and Love Signs (1978); Hair: The
American Tribal Love-Rock Musical (1967) with the opening song "
Aquarius " and its memorable line " This is the dawning of the Age
of Aquarius " [emphasis added]; the broadcast of Shirley MacLaine
's television mini-series Out on a Limb (1987); and the Harmonic
Convergence (1987) organized by José Argüelles in
Sedona , Arizona . Also influential were the claims of channelers
Jane Roberts (the Seth Material ) and J. Z. Knight ( Ramtha ), as
well as revealed writings A Course in Miracles (1976) by Helen
Schucman , The Celestine Prophecy (1993) by James Redfield , and
Conversations with God (1995) by Neale Donald Walsch . Relevant
works also include the writings of Eckhart Tolle , Barbara Marx
Hubbard , Marianne Williamson , Deepak Chopra , John Holland , Gary
Zukav , and Wayne Dyer ; also, The Secret (2006) by Rhonda Byrne ,
which was based on the writings of Esther Hicks and Jerry Hicks.
The New Age (also referred to as the New Age movement , New Age
spirituality , and Cosmic Humanism ) is a decentralized Western
social and spiritual movement that seeks " Universal Truth " and
the attainment of the highest individual human potential . It
includes aspects of Occultism , astrology , esotericism ,
metaphysics , alternative medicine , music , collectivism ,
sustainability , and nature . New Age spirituality is characterized
by an individual approach to spiritual practices and philosophies,
and the rejection of religious doctrine and dogma .
The New Age movement includes elements of older spiritual and
religious traditions ranging from atheism and monotheism through
classical pantheism , naturalistic pantheism , and panentheism to
polytheism combined with science and Gaia philosophy : particularly
archaeoastronomy , astronomy , ecology , environmentalism , the
Gaia hypothesis , psychology , and physics . New Age practices and
philosophies sometimes draw inspiration from major world religions
: Buddhism , Chinese folk religion , Christianity , Hinduism ,
Islam , Judaism ; with particularly strong influences from East
Asian religions , Gnosticism , Neopaganism , New Thought ,
Spiritualism , Theosophy , Universalism , and Western esotericism .
[ 2 ] Additional terms for the movement include All is One [ 3 ]
and Mind-Body-Spirit . [ 1 ]
The modern New Age movement emerged in a distinct form in the late
1960s and early 1970s, although its roots can be traced back to the
19th and early 20th centuries. It gained momentum in the 1980s and
strengthened with the Harmonic Convergence event in 1987. Diverse
individuals from around the world practice New Age spirituality. [
citation needed ]
Contents
1 Movement
1.1 Origins
1.2 Development
1.3 Postmodern
2 Spirituality
2.1 Philosophy and cosmology
2.2 Religion and science
3 Lifestyle
3.1 Demographics
3.2 Holistic health
3.3 Music
3.4 Sustainable living
4 Reception
4.1 Organized religion
4.2 Integral Theory
4.3 Indigenous peoples of the Americas
5 In popular culture
6 See also
7 Notes
8 References
9 Further reading
10 External links
//
Movement
Origins
See also: List of Neopagan movements , List of new religious
movements , and List of religions and spiritual traditions
The term New Age was used as early as 1809 by William Blake who
described a belief in a spiritual and artistic "New Age" in his
preface to Milton: a Poem .
Some of the New Age movement's constituent elements appeared
initially in 19th century metaphysical movements: Spiritualism ,
Theosophy , and New Thought ; also, alternative medicine movements
chiropractic and naturopathy . [ 1 ] [ 3 ] These movements in turn
have roots in Transcendentalism , Mesmerism , Swedenborgianism ,
and various earlier Western esoteric or occult traditions, such as
the hermetic arts of astrology, magic , alchemy , and Kabbalah .
The term New Age was used in this context in Madame Blavatsky 's
book The Secret Doctrine , published in 1888. [ 4 ]
A weekly journal of Christian liberalism and socialism titled The
New Age was published as early as 1894; [ 5 ] it was sold to a
group of socialist writers headed by Alfred Richard Orage and
Holbrook Jackson in 1907. Other historical personalities were
involved: H. G. Wells , George Bernard Shaw , and William Butler
Yeats ; the magazine became a forum for politics , literature , and
the arts . [ 6 ] [ 7 ] Between 1908 and 1914, it was instrumental
in pioneering the British avant-garde from vorticism to imagism .
After 1914, publisher Orage met P. D. Ouspensky , a follower of G.
I. Gurdjieff , and began correspondence with Harry Houdini ,
becoming less interested in literature and art, with an increased
focus on mysticism and other spiritual topics; the magazine was
sold in 1921. According to Brown University , The New Age "...
helped to shape modernism in literature and the arts from 1907 to
1922." [ 8 ]
Development
Popularisation behind these ideas has roots in the work of early
20th century writers such as D. H. Lawrence and William Butler
Yeats . In the early to middle 1900s, American mystic, theologian,
and founder of the Association for Research and Enlightenment Edgar
Cayce was a seminal influence on what later would be termed the New
Age movement ; he was known in particular for the practice some
refer to as channeling . [ 9 ] Former Theosophist Rudolf Steiner
and his Anthroposophical Movement are a major influence.
Neo-Theosophist Alice Bailey published the book Discipleship in the
New Age (1944), which used the term New Age in reference to the
transition from the Astrological Age of Pisces to Aquarius . While
claims of racial bias in the writings of Rudolf Steiner and Alice
Bailey were made, [ 10 ] Steiner emphasized racial equality as a
principle central to anthroposophical thought and humanity 's
progress. [ 11 ] [ 12 ] Any racial elements from these influences
have not remained part of the Anthroposophical Society as
contemporary adherents of the society have either not adopted or
repudiated these beliefs. [ 13 ] [ 14 ] Another early usage of the
term, was by the American artist, mystic, and philosopher Walter
Russell , who spoke of "... this New Age philosophy of the
spiritual re-awakening of man ..." in his essay "Power Through
Knowledge", which was also published in 1944.
Carl Gustav Jung was an early articulator of the concept of the Age
of Aquarius. [ 15 ] In a letter to H. G. Baynes, dated 12 August
1940, he wrote in a passage concerning the destruction of the
temple of Karnak by an earthquake in 26 BC: "1940 is the year when
we approach the meridian of the first star in Aquarius . It is the
premonitory earthquake of the New Age." [ 16 ]
Postmodern
Main article: Postmodernism
A barrel house—the first dwelling constructed at the Findhorn
Ecovillage
The subculture that would later be called New Age already existed
in the early 1970s, based on and adopting ideas originally present
in the counterculture of the 1960s . The Findhorn Foundation
– an intentional community near Findhorn , Moray , Scotland
founded in 1962 – played an instrumental role during the
early growth period of the New Age movement; it continues to
operate the Findhorn Ecovillage .
Widespread use of the term New Age began in the mid 1970s
(reflected in the title of monthly periodical New Age Journal ) and
probably influenced several thousand small metaphysical book and
gift stores that increasingly defined themselves as "New Age
bookstores". [ 17 ] [ 18 ] As a result of the large-scale
activities surrounding the Harmonic Convergence in the mid 1980s
– the term was further popularised by the American mass media
to describe the alternative spiritual subculture – including
practices such as meditation , channeling, crystal healing , astral
projection , psychic experience, holistic health , simple living ,
and environmentalism; or belief in phenomena such as Earth
mysteries , ancient astronauts , extraterrestrial life ,
unidentified flying objects , crop circles , and reincarnation . A
range of New Age publications appeared by the late 1980s such as
Psychic Guide (later renamed Body, Mind & Spirit ), Yoga
Journal , New Age Voice , New Age Retailer , and NAPRA ReView by
the New Age Publishers and Retailers Alliance.
There were several key moments in raising public awareness of this
subculture: the publication of Linda Goodman 's best selling
astrology books Sun Signs (1968) and Love Signs (1978); Hair: The
American Tribal Love-Rock Musical (1967) with the opening song "
Aquarius " and its memorable line " This is the dawning of the Age
of Aquarius " [emphasis added]; the broadcast of Shirley MacLaine
's television mini-series Out on a Limb (1987); and the Harmonic
Convergence (1987) organized by José Argüelles in
Sedona , Arizona . Also influential were the claims of channelers
Jane Roberts (the Seth Material ) and J. Z. Knight ( Ramtha ), as
well as revealed writings A Course in Miracles (1976) by Helen
Schucman , The Celestine Prophecy (1993) by James Redfield , and
Conversations with God (1995) by Neale Donald Walsch . Relevant
works also include the writings of Eckhart Tolle , Barbara Marx
Hubbard , Marianne Williamson , Deepak Chopra , John Holland , Gary
Zukav , and Wayne Dyer ; also, The Secret (2006) by Rhonda Byrne ,
which was based on the writings of Esther Hicks and Jerry Hicks.
The New Age (also referred to as the New Age movement , New Age
spirituality , and Cosmic Humanism ) is a decentralized Western
social and spiritual movement that seeks " Universal Truth " and
the attainment of the highest individual human potential . It
includes aspects of Occultism , astrology , esotericism ,
metaphysics , alternative medicine , music , collectivism ,
sustainability , and nature . New Age spirituality is characterized
by an individual approach to spiritual practices and philosophies,
and the rejection of religious doctrine and dogma .
The New Age movement includes elements of older spiritual and
religious traditions ranging from atheism and monotheism through
classical pantheism , naturalistic pantheism , and panentheism to
polytheism combined with science and Gaia philosophy : particularly
archaeoastronomy , astronomy , ecology , environmentalism , the
Gaia hypothesis , psychology , and physics . New Age practices and
philosophies sometimes draw inspiration from major world religions
: Buddhism , Chinese folk religion , Christianity , Hinduism ,
Islam , Judaism ; with particularly strong influences from East
Asian religions , Gnosticism , Neopaganism , New Thought ,
Spiritualism , Theosophy , Universalism , and Western esotericism .
[ 2 ] Additional terms for the movement include All is One [ 3 ]
and Mind-Body-Spirit . [ 1 ]
The modern New Age movement emerged in a distinct form in the late
1960s and early 1970s, although its roots can be traced back to the
19th and early 20th centuries. It gained momentum in the 1980s and
strengthened with the Harmonic Convergence event in 1987. Diverse
individuals from around the world practice New Age spirituality. [
citation needed ]
Contents
1 Movement
1.1 Origins
1.2 Development
1.3 Postmodern
2 Spirituality
2.1 Philosophy and cosmology
2.2 Religion and science
3 Lifestyle
3.1 Demographics
3.2 Holistic health
3.3 Music
3.4 Sustainable living
4 Reception
4.1 Organized religion
4.2 Integral Theory
4.3 Indigenous peoples of the Americas
5 In popular culture
6 See also
7 Notes
8 References
9 Further reading
10 External links
//
Movement
Origins
See also: List of Neopagan movements , List of new religious
movements , and List of religions and spiritual traditions
The term New Age was used as early as 1809 by William Blake who
described a belief in a spiritual and artistic "New Age" in his
preface to Milton: a Poem .
Some of the New Age movement's constituent elements appeared
initially in 19th century metaphysical movements: Spiritualism ,
Theosophy , and New Thought ; also, alternative medicine movements
chiropractic and naturopathy . [ 1 ] [ 3 ] These movements in turn
have roots in Transcendentalism , Mesmerism , Swedenborgianism ,
and various earlier Western esoteric or occult traditions, such as
the hermetic arts of astrology, magic , alchemy , and Kabbalah .
The term New Age was used in this context in Madame Blavatsky 's
book The Secret Doctrine , published in 1888. [ 4 ]
A weekly journal of Christian liberalism and socialism titled The
New Age was published as early as 1894; [ 5 ] it was sold to a
group of socialist writers headed by Alfred Richard Orage and
Holbrook Jackson in 1907. Other historical personalities were
involved: H. G. Wells , George Bernard Shaw , and William Butler
Yeats ; the magazine became a forum for politics , literature , and
the arts . [ 6 ] [ 7 ] Between 1908 and 1914, it was instrumental
in pioneering the British avant-garde from vorticism to imagism .
After 1914, publisher Orage met P. D. Ouspensky , a follower of G.
I. Gurdjieff , and began correspondence with Harry Houdini ,
becoming less interested in literature and art, with an increased
focus on mysticism and other spiritual topics; the magazine was
sold in 1921. According to Brown University , The New Age "...
helped to shape modernism in literature and the arts from 1907 to
1922." [ 8 ]
Development
Popularisation behind these ideas has roots in the work of early
20th century writers such as D. H. Lawrence and William Butler
Yeats . In the early to middle 1900s, American mystic, theologian,
and founder of the Association for Research and Enlightenment Edgar
Cayce was a seminal influence on what later would be termed the New
Age movement ; he was known in particular for the practice some
refer to as channeling . [ 9 ] Former Theosophist Rudolf Steiner
and his Anthroposophical Movement are a major influence.
Neo-Theosophist Alice Bailey published the book Discipleship in the
New Age (1944), which used the term New Age in reference to the
transition from the Astrological Age of Pisces to Aquarius . While
claims of racial bias in the writings of Rudolf Steiner and Alice
Bailey were made, [ 10 ] Steiner emphasized racial equality as a
principle central to anthroposophical thought and humanity 's
progress. [ 11 ] [ 12 ] Any racial elements from these influences
have not remained part of the Anthroposophical Society as
contemporary adherents of the society have either not adopted or
repudiated these beliefs. [ 13 ] [ 14 ] Another early usage of the
term, was by the American artist, mystic, and philosopher Walter
Russell , who spoke of "... this New Age philosophy of the
spiritual re-awakening of man ..." in his essay "Power Through
Knowledge", which was also published in 1944.
Carl Gustav Jung was an early articulator of the concept of the Age
of Aquarius. [ 15 ] In a letter to H. G. Baynes, dated 12 August
1940, he wrote in a passage concerning the destruction of the
temple of Karnak by an earthquake in 26 BC: "1940 is the year when
we approach the meridian of the first star in Aquarius . It is the
premonitory earthquake of the New Age." [ 16 ]
Postmodern
Main article: Postmodernism
A barrel house—the first dwelling constructed at the Findhorn
Ecovillage
The subculture that would later be called New Age already existed
in the early 1970s, based on and adopting ideas originally present
in the counterculture of the 1960s . The Findhorn Foundation
– an intentional community near Findhorn , Moray , Scotland
founded in 1962 – played an instrumental role during the
early growth period of the New Age movement; it continues to
operate the Findhorn Ecovillage .
Widespread use of the term New Age began in the mid 1970s
(reflected in the title of monthly periodical New Age Journal ) and
probably influenced several thousand small metaphysical book and
gift stores that increasingly defined themselves as "New Age
bookstores". [ 17 ] [ 18 ] As a result of the large-scale
activities surrounding the Harmonic Convergence in the mid 1980s
– the term was further popularised by the American mass media
to describe the alternative spiritual subculture – including
practices such as meditation , channeling, crystal healing , astral
projection , psychic experience, holistic health , simple living ,
and environmentalism; or belief in phenomena such as Earth
mysteries , ancient astronauts , extraterrestrial life ,
unidentified flying objects , crop circles , and reincarnation . A
range of New Age publications appeared by the late 1980s such as
Psychic Guide (later renamed Body, Mind & Spirit ), Yoga
Journal , New Age Voice , New Age Retailer , and NAPRA ReView by
the New Age Publishers and Retailers Alliance.
There were several key moments in raising public awareness of this
subculture: the publication of Linda Goodman 's best selling
astrology books Sun Signs (1968) and Love Signs (1978); Hair: The
American Tribal Love-Rock Musical (1967) with the opening song "
Aquarius " and its memorable line " This is the dawning of the Age
of Aquarius " [emphasis added]; the broadcast of Shirley MacLaine
's television mini-series Out on a Limb (1987); and the Harmonic
Convergence (1987) organized by José Argüelles in
Sedona , Arizona . Also influential were the claims of channelers
Jane Roberts (the Seth Material ) and J. Z. Knight ( Ramtha ), as
well as revealed writings A Course in Miracles (1976) by Helen
Schucman , The Celestine Prophecy (1993) by James Redfield , and
Conversations with God (1995) by Neale Donald Walsch . Relevant
works also include the writings of Eckhart Tolle , Barbara Marx
Hubbard , Marianne Williamson , Deepak Chopra , John Holland , Gary
Zukav , and Wayne Dyer ; also, The Secret (2006) by Rhonda Byrne ,
which was based on the writings of Esther Hicks and Jerry Hicks.
The New Age (also referred to as the New Age movement , New Age
spirituality , and Cosmic Humanism ) is a decentralized Western
social and spiritual movement that seeks " Universal Truth " and
the attainment of the highest individual human potential . It
includes aspects of Occultism , astrology , esotericism ,
metaphysics , alternative medicine , music , collectivism ,
sustainability , and nature . New Age spirituality is characterized
by an individual approach to spiritual practices and philosophies,
and the rejection of religious doctrine and dogma .
The New Age movement includes elements of older spiritual and
religious traditions ranging from atheism and monotheism through
classical pantheism , naturalistic pantheism , and panentheism to
polytheism combined with science and Gaia philosophy : particularly
archaeoastronomy , astronomy , ecology , environmentalism , the
Gaia hypothesis , psychology , and physics . New Age practices and
philosophies sometimes draw inspiration from major world religions
: Buddhism , Chinese folk religion , Christianity , Hinduism ,
Islam , Judaism ; with particularly strong influences from East
Asian religions , Gnosticism , Neopaganism , New Thought ,
Spiritualism , Theosophy , Universalism , and Western esotericism .
[ 2 ] Additional terms for the movement include All is One [ 3 ]
and Mind-Body-Spirit . [ 1 ]
The modern New Age movement emerged in a distinct form in the late
1960s and early 1970s, although its roots can be traced back to the
19th and early 20th centuries. It gained momentum in the 1980s and
strengthened with the Harmonic Convergence event in 1987. Diverse
individuals from around the world practice New Age spirituality. [
citation needed ]
Contents
1 Movement
1.1 Origins
1.2 Development
1.3 Postmodern
2 Spirituality
2.1 Philosophy and cosmology
2.2 Religion and science
3 Lifestyle
3.1 Demographics
3.2 Holistic health
3.3 Music
3.4 Sustainable living
4 Reception
4.1 Organized religion
4.2 Integral Theory
4.3 Indigenous peoples of the Americas
5 In popular culture
6 See also
7 Notes
8 References
9 Further reading
10 External links
//
Movement
Origins
See also: List of Neopagan movements , List of new religious
movements , and List of religions and spiritual traditions
The term New Age was used as early as 1809 by William Blake who
described a belief in a spiritual and artistic "New Age" in his
preface to Milton: a Poem .
Some of the New Age movement's constituent elements appeared
initially in 19th century metaphysical movements: Spiritualism ,
Theosophy , and New Thought ; also, alternative medicine movements
chiropractic and naturopathy . [ 1 ] [ 3 ] These movements in turn
have roots in Transcendentalism , Mesmerism , Swedenborgianism ,
and various earlier Western esoteric or occult traditions, such as
the hermetic arts of astrology, magic , alchemy , and Kabbalah .
The term New Age was used in this context in Madame Blavatsky 's
book The Secret Doctrine , published in 1888. [ 4 ]
A weekly journal of Christian liberalism and socialism titled The
New Age was published as early as 1894; [ 5 ] it was sold to a
group of socialist writers headed by Alfred Richard Orage and
Holbrook Jackson in 1907. Other historical personalities were
involved: H. G. Wells , George Bernard Shaw , and William Butler
Yeats ; the magazine became a forum for politics , literature , and
the arts . [ 6 ] [ 7 ] Between 1908 and 1914, it was instrumental
in pioneering the British avant-garde from vorticism to imagism .
After 1914, publisher Orage met P. D. Ouspensky , a follower of G.
I. Gurdjieff , and began correspondence with Harry Houdini ,
becoming less interested in literature and art, with an increased
focus on mysticism and other spiritual topics; the magazine was
sold in 1921. According to Brown University , The New Age "...
helped to shape modernism in literature and the arts from 1907 to
1922." [ 8 ]
Development
Popularisation behind these ideas has roots in the work of early
20th century writers such as D. H. Lawrence and William Butler
Yeats . In the early to middle 1900s, American mystic, theologian,
and founder of the Association for Research and Enlightenment Edgar
Cayce was a seminal influence on what later would be termed the New
Age movement ; he was known in particular for the practice some
refer to as channeling . [ 9 ] Former Theosophist Rudolf Steiner
and his Anthroposophical Movement are a major influence.
Neo-Theosophist Alice Bailey published the book Discipleship in the
New Age (1944), which used the term New Age in reference to the
transition from the Astrological Age of Pisces to Aquarius . While
claims of racial bias in the writings of Rudolf Steiner and Alice
Bailey were made, [ 10 ] Steiner emphasized racial equality as a
principle central to anthroposophical thought and humanity 's
progress. [ 11 ] [ 12 ] Any racial elements from these influences
have not remained part of the Anthroposophical Society as
contemporary adherents of the society have either not adopted or
repudiated these beliefs. [ 13 ] [ 14 ] Another early usage of the
term, was by the American artist, mystic, and philosopher Walter
Russell , who spoke of "... this New Age philosophy of the
spiritual re-awakening of man ..." in his essay "Power Through
Knowledge", which was also published in 1944.
Carl Gustav Jung was an early articulator of the concept of the Age
of Aquarius. [ 15 ] In a letter to H. G. Baynes, dated 12 August
1940, he wrote in a passage concerning the destruction of the
temple of Karnak by an earthquake in 26 BC: "1940 is the year when
we approach the meridian of the first star in Aquarius . It is the
premonitory earthquake of the New Age." [ 16 ]
Postmodern
Main article: Postmodernism
A barrel house—the first dwelling constructed at the Findhorn
Ecovillage
The subculture that would later be called New Age already existed
in the early 1970s, based on and adopting ideas originally present
in the counterculture of the 1960s . The Findhorn Foundation
– an intentional community near Findhorn , Moray , Scotland
founded in 1962 – played an instrumental role during the
early growth period of the New Age movement; it continues to
operate the Findhorn Ecovillage .
Widespread use of the term New Age began in the mid 1970s
(reflected in the title of monthly periodical New Age Journal ) and
probably influenced several thousand small metaphysical book and
gift stores that increasingly defined themselves as "New Age
bookstores". [ 17 ] [ 18 ] As a result of the large-scale
activities surrounding the Harmonic Convergence in the mid 1980s
– the term was further popularised by the American mass media
to describe the alternative spiritual subculture – including
practices such as meditation , channeling, crystal healing , astral
projection , psychic experience, holistic health , simple living ,
and environmentalism; or belief in phenomena such as Earth
mysteries , ancient astronauts , extraterrestrial life ,
unidentified flying objects , crop circles , and reincarnation . A
range of New Age publications appeared by the late 1980s such as
Psychic Guide (later renamed Body, Mind & Spirit ), Yoga
Journal , New Age Voice , New Age Retailer , and NAPRA ReView by
the New Age Publishers and Retailers Alliance.
There were several key moments in raising public awareness of this
subculture: the publication of Linda Goodman 's best selling
astrology books Sun Signs (1968) and Love Signs (1978); Hair: The
American Tribal Love-Rock Musical (1967) with the opening song "
Aquarius " and its memorable line " This is the dawning of the Age
of Aquarius " [emphasis added]; the broadcast of Shirley MacLaine
's television mini-series Out on a Limb (1987); and the Harmonic
Convergence (1987) organized by José Argüelles in
Sedona , Arizona . Also influential were the claims of channelers
Jane Roberts (the Seth Material ) and J. Z. Knight ( Ramtha ), as
well as revealed writings A Course in Miracles (1976) by Helen
Schucman , The Celestine Prophecy (1993) by James Redfield , and
Conversations with God (1995) by Neale Donald Walsch . Relevant
works also include the writings of Eckhart Tolle , Barbara Marx
Hubbard , Marianne Williamson , Deepak Chopra , John Holland , Gary
Zukav , and Wayne Dyer ; also, The Secret (2006) by Rhonda Byrne ,
which was based on the writings of Esther Hicks and Jerry Hicks.
A water ionizer is an appliance that ionizes water . Ionized water
is purported to be beneficial to human health and marketed with
claims that it is an antioxidant which can slow aging and prevent
disease. [ 1 ] Others note that such claims contradict basic laws
of chemistry and physiology. [ 2 ]
Contents
1 Ionization
2 Uses
3 See also
4 References
5 External links
//
Ionization
Main article: Electrolysis of water
A water ionizer separates water into alkaline and acid fractions
using a process known as electrolysis . [ 3 ] It does this by
exploiting the electric charge of the calcium and magnesium ions
present in nearly all sources of drinking water. When a source of
water lacks mineral ions, such as distilled water , or has been
filtered by reverse osmosis , water ionization has no effect.
Uses
Some research suggests that alkaline reduced water may be useful in
scavenging free radicals in the laboratory setting. [ 4 ] Tests on
in vitro lymphocytes suggest that reduced water can prevent
hydrogen peroxide -induced damage to DNA , RNA and certain proteins
. [ 5 ] However, drinking ionized water would not be expected to
alter the body's pH , and there is no evidence of any claims made
by manufacturers that drinking ionized water will have a noticeable
effect on the body. [ 2 ]
Electrolyzed water has been used by the food industry to sanitize
food products; though effective in bacterial solutions, it was
found less useful when sanitizing utensils, surfaces and food
products. [ 6 ] [ 7 ] Acidic electrolyzed water (pH 2.3–2.6)
may have use as a seed surface disinfectant or contact bactericide
. [ 8 ]
In typical usage, water refers only to its liquid form or state ,
but the substance also has a solid state, ice , and a gaseous
state, water vapor or steam . Water covers 71% of the Earth 's
surface [ 2 ] . On Earth, it is found mostly in oceans and other
large water bodies, with 1.6% of water below ground in aquifers and
0.001% in the air as vapor , clouds (formed of solid and liquid
water particles suspended in air), and precipitation . [ 3 ] Oceans
hold 97% of surface water, glaciers and polar ice caps 2.4%, and
other land surface water such as rivers , lakes and ponds 0.6%. A
very small amount of the Earth's water is contained within
biological bodies and manufactured products.
Water on Earth moves continually through a cycle of evaporation or
transpiration ( evapotranspiration ), precipitation , and runoff ,
usually reaching the sea . Over land, evaporation and transpiration
contribute to the precipitation over land.
Clean, fresh drinking water is essential to human and other
lifeforms. Access to safe drinking water has improved steadily and
substantially over the last decades in almost every part of the
world. [ 4 ] [ 5 ] There is a clear correlation between access to
safe water and GDP per capita. [ 6 ] However, some observers have
estimated that by 2025 more than half of the world population will
be facing water-based vulnerability. [ 7 ] A recent report
(November 2009) suggests that by 2030, in some developing regions
of the world, water demand will exceed supply by 50%. [ 8 ] Water
plays an important role in the world economy , as it functions as a
solvent for a wide variety of chemical substances and facilitates
industrial cooling and transportation. Approximately 70% of
freshwater is consumed by agriculture . [ 9 ]
Contents
1 Chemical and physical properties
2 Taste and odor
3 Distribution of water in nature
3.1 Water in the universe
3.2 Water and habitable zone
4 Water on Earth
4.1 Water cycle
4.2 Fresh water storage
4.3 Sea water
4.4 Tides
5 Effects on life
5.1 Aquatic life forms
6 Effects on human civilization
6.1 Health and pollution
6.2 Human uses
6.2.1 Agriculture
6.2.2 Water as a scientific standard
6.2.3 For drinking
6.2.4 Hygiene
6.2.5 Chemical uses
6.2.6 As a heat transfer fluid
6.2.7 Extinguishing fires
6.2.8 Recreation
6.2.9 Water industry
6.2.10 Industrial applications
6.2.11 Food processing
7 Water law, water politics and water crisis
8 Water in culture
8.1 Religion
8.2 Philosophy
8.3 Literature
9 See also
9.1 Other topics
10 References
11 Further reading
11.1 Water as a natural resource
12 External links
//
Chemical and physical properties
Main articles: Water (properties) , Water (data page) , and Water
model
Model of hydrogen bonds between molecules of water
Impact from a water drop causes an upward "rebound" jet surrounded
by circular capillary waves .
Snowflakes by Wilson Bentley , 1902
Dew drops adhering to a spider web
Capillary action of water compared to mercury
Water is the chemical substance with chemical formula H 2 O : one
molecule of water has two hydrogen atoms covalently bonded to a
single oxygen atom.
Water appears in nature in all three common states of matter and
may take many different forms on Earth: water vapor and clouds in
the sky; seawater and icebergs in the polar oceans; glaciers and
rivers in the mountains ; and the liquid in aquifers in the
ground.
The major chemical and physical properties of water are:
Water is a tasteless, odorless liquid at standard temperature and
pressure . The color of water and ice is, intrinsically, a very
light blue hue, although water appears colorless in small
quantities. Ice also appears colorless, and water vapor is
essentially invisible as a gas. [ 10 ]
Water is transparent , and thus aquatic plants can live within the
water because sunlight can reach them. Only strong UV light is
slightly absorbed .
Since the water molecule is not linear and the oxygen atom has a
higher electronegativity than hydrogen atoms, it carries a slight
negative charge, whereas the hydrogen atoms are slightly positive.
As a result, water is a polar molecule with an electrical dipole
moment . The net interactions between the dipoles on each molecule
cause an effective skin effect at the interface of water with other
substances, or air at the surface, the latter given rise to water's
high surface tension . This dipolar nature contributes to water
molecules' tendency to form hydrogen bonds which cause water's many
special properties. [ 11 ] The polar nature also favors adhesion to
other materials.
Each hydrogen nucleus is bound to the central oxygen atom by a pair
of electrons that are shared between them; chemists call this
shared electron pair a covalent chemical bond. In H 2 O, only two
of the six outer-shell electrons of oxygen are used for this
purpose, leaving four electrons which are organized into two
non-bonding pairs. The four electron pairs surrounding the oxygen
tend to arrange themselves as far from each other as possible in
order to minimize repulsions between these clouds of negative
charge. This would ordinarily result in a tetrahedral geometry in
which the angle between electron pairs (and therefore the H-O-H
bond angle) is 109.5°. However, because the two non-bonding
pairs remain closer to the oxygen atom, these exert a stronger
repulsion against the two covalent bonding pairs, effectively
pushing the two hydrogen atoms closer together. The result is a
distorted tetrahedral arrangement in which the H-O-H angle is
104.5°. [ 12 ]
A result of interplay of these properties, Capillary action refers
to the tendency of water to move up a narrow tube against the force
of gravity . This property is relied upon by all vascular plants ,
such as trees.
Water is a good solvent and is often referred to as the universal
solvent . Substances that dissolve in water, e.g., salts , sugars ,
acids , alkalis , and some gases – especially oxygen, carbon
dioxide ( carbonation ) are known as hydrophilic (water-loving)
substances, while those that do not mix well with water (e.g., fats
and oils ), are known as hydrophobic (water-fearing)
substances.
All the major components in cells ( proteins , DNA and
polysaccharides ) are also dissolved in water.
Pure water has a low electrical conductivity , but this increases
significantly with the dissolution of a small amount of ionic
material such as sodium chloride .
The boiling point of water (and all other liquids) is dependent on
the barometric pressure . For example, on the top of Mt. Everest
water boils at about 68 °C (154 °F), compared to
100 °C (212 °F) at sea level . Conversely, water
deep in the ocean near geothermal vents can reach temperatures of
hundreds of degrees and remain liquid.
Water has the second highest specific heat capacity of any known
substance, after ammonia , as well as a high heat of vaporization
(40.65 kJ·mol −1 ), both of which are a result of
the extensive hydrogen bonding between its molecules. These two
unusual properties allow water to moderate Earth's climate by
buffering large fluctuations in temperature.
The maximum density of water occurs at 3.98 °C
(39.16 °F). [ 13 ] Water becomes even less dense upon
freezing, expanding 9%. This results in an unusual phenomenon:
water's solid form, ice, floats upon water, allowing organisms to
survive inside a partially-frozen water body because the water on
the bottom has a temperature of around 4 °C
(39 °F).
ADR label for transporting goods dangerously reactive with
water
Water is miscible with many liquids, such as ethanol , in all
proportions, forming a single homogeneous liquid. On the other
hand, water and most oils are immiscible usually forming layers
according to increasing density from the top. As a gas, water vapor
is completely miscible with air.
Water forms an azeotrope with many other solvents.
Water can be split by electrolysis into hydrogen and oxygen.
As an oxide of hydrogen, water is formed when hydrogen or
hydrogen-containing compounds burn or react with oxygen or
oxygen-containing compounds. Water is not a fuel , it is an
end-product of the combustion of hydrogen. The energy required to
split water into hydrogen and oxygen by electrolysis or any other
means is greater than the energy released when the hydrogen and
oxygen recombine. [ 14 ]
Elements which are more electropositive than hydrogen such as
lithium , sodium , calcium , potassium and caesium displace
hydrogen from water, forming hydroxides . Being a flammable gas,
the hydrogen given off is dangerous and the reaction of water with
the more electropositive of these elements may be violently
explosive.
Taste and odor
Water can dissolve many different substances, giving it varying
tastes and odors. Humans and other animals have developed senses
which (more or less) enable them to evaluate the potability of
water by avoiding water that is too salty or putrid . Humans also
tend to prefer cold water to lukewarm water since cold water is
likely to contain fewer microbes . The taste advertised in spring
water or mineral water derives from the minerals dissolved in it:
Pure H 2 O is tasteless and odorless. The advertised purity of
spring and mineral water refers to absence of toxins , pollutants
and microbes .
Distribution of water in nature
Water in the universe
Much of the universe's water may be produced as a byproduct of star
formation . When stars are born, their birth is accompanied by a
strong outward wind of gas and dust. When this outflow of material
eventually impacts the surrounding gas, the shock waves that are
created compress and heat the gas. The water observed is quickly
produced in this warm dense gas. [ 15 ]
Water has been detected in interstellar clouds within our galaxy ,
the Milky Way . Water probably exists in abundance in other
galaxies, too, because its components, hydrogen and oxygen, are
among the most abundant elements in the universe. Interstellar
clouds eventually condense into solar nebulae and solar systems
such as ours.
Water vapor is present in:
Atmosphere of Mercury : 3.4%, and large amounts of water in
Mercury's exosphere [ 16 ]
Atmosphere of Venus : 0.002%
Earth's atmosphere : ~0.40% over full atmosphere, typically 1%-4%
at surface
Atmosphere of Mars : 0.03%
Atmosphere of Jupiter : 0.0004%
Atmosphere of Saturn - in ices only
Enceladus (moon of Saturn): 91%
exoplanets known as HD 189733 b [ 17 ] and HD 209458 b . [ 18 ]
Liquid water is present on:
Earth - 71% of surface
Moon - small amounts of water have been found (in 2008) in the
inside of volcanic pearls brought from Moon to Earth by the Apollo
15 crew in 1971. [ 19 ] NASA reported the detection of water
molecules by NASA's Moon Mineralogy Mapper aboard the Indian Space
Research Organization's Chandrayaan-1 spacecraft in September 2009.
[ 20 ]
Strong evidence suggests that liquid water is present just under
the surface of Saturn's moon Enceladus and on Jupiter's moon Europa
where it may exist as a 100 km deep ocean covering the whole
moon which would amount to more water than is in all the Earth's
oceans.
Water ice is present on:
Earth - mainly as ice sheets
polar ice caps on Mars
Moon
Titan
Europa
Saturn's rings [ 21 ]
Enceladus
Pluto and Charon [ 22 ]
Comets and comet source populations ( Kuiper belt and Oort cloud
objects).
Water ice may be present on Ceres and Tethys . Water and other
volatiles probably comprise much of the internal structures of
Uranus and Neptune .
Water and habitable zone
The Solar System along center row range of possible habitable zones
of varying size stars.
The existence of liquid water, and to a lesser extent its gaseous
and solid forms, on Earth are vital to the existence of life on
Earth as we know it. The Earth is located in the habitable zone of
the solar system ; if it were slightly closer to or further from
the Sun (about 5%, or about 8 million kilometers), the conditions
which allow the three forms to be present simultaneously would be
far less likely to exist. [ 23 ] [ 24 ]
Earth's gravity allows it to hold an atmosphere . Water vapor and
carbon dioxide in the atmosphere provide a temperature buffer (
greenhouse effect ) which helps maintain a relatively steady
surface temperature. If Earth were smaller, a thinner atmosphere
would allow temperature extremes, thus preventing the accumulation
of water except in polar ice caps (as on Mars ).
The surface temperature of Earth has been relatively constant
through geologic time despite varying levels of incoming solar
radiation ( insolation ), indicating that a dynamic process governs
Earth's temperature via a combination of greenhouse gases and
surface or atmospheric albedo . This proposal is known as the Gaia
hypothesis .
The state of water on a planet depends on ambient pressure, which
is determined by the planet's gravity. If a planet is sufficiently
massive, the water on it may be solid even at high temperatures,
because of the high pressure caused by gravity.
There are various theories about origin of water on Earth .
Water on Earth
Main articles: Hydrology and Water distribution on Earth
A graphical distribution of the locations of water on Earth.
Water covers 71% of the Earth's surface; the oceans contain 97.2%
of the Earth's water. The Antarctic ice sheet , which contains 90%
of all fresh water on Earth, is visible at the bottom. Condensed
atmospheric water can be seen as clouds , contributing to the
Earth's albedo .
Hydrology is the study of the movement, distribution, and quality
of water throughout the Earth. The study of the distribution of
water is hydrography . The study of the distribution and movement
of groundwater is hydrogeology , of glaciers is glaciology , of
inland waters is limnology and distribution of oceans is
oceanography . Ecological processes with hydrology are in focus of
ecohydrology .
The collective mass of water found on, under, and over the surface
of a planet is called the hydrosphere . Earth's approximate water
volume (the total water supply of the world) is
1,360,000,000 km 3 (326,000,000 mi 3 ).
Groundwater and fresh water are useful or potentially useful to
humans as water resources .
Liquid water is found in bodies of water , such as an ocean, sea ,
lake , river , stream , canal , pond , or puddle . The majority of
water on Earth is sea water . Water is also present in the
atmosphere in solid, liquid, and vapor states. It also exists as
groundwater in aquifers .
Water is important in many geological processes. Groundwater is
ubiquitous in rocks , and the pressure of this groundwater affects
patterns of faulting . Water in the mantle is responsible for the
melt that produces volcanoes at subduction zones . On the surface
of the Earth, water is important in both chemical and physical
weathering processes. Water and, to a lesser but still significant
extent, ice, are also responsible for a large amount of sediment
transport that occurs on the surface of the earth. Deposition of
transported sediment forms many types of sedimentary rocks , which
make up the geologic record of Earth history .
Water cycle
Main article: Water cycle
Water cycle
The water cycle (known scientifically as the hydrologic cycle )
refers to the continuous exchange of water within the hydrosphere ,
between the atmosphere , soil water, surface water , groundwater ,
and plants .
Water moves perpetually through each of these regions in the water
cycle consisting of following transfer processes:
evaporation from oceans and other water bodies into the air and
transpiration from land plants and animals into air.
precipitation , from water vapor condensing from the air and
falling to earth or ocean.
runoff from the land usually reaching the sea .
Most water vapor over the oceans returns to the oceans, but winds
carry water vapor over land at the same rate as runoff into the
sea, about 36 Tt per year. Over land, evaporation and
transpiration contribute another 71 Tt per year.
Precipitation, at a rate of 107 Tt per year over land, has several
forms: most commonly rain , snow , and hail , with some
contribution from fog and dew . Condensed water in the air may also
refract sunlight to produce rainbows .
Water runoff often collects over watersheds flowing into rivers. A
mathematical model used to simulate river or stream flow and
calculate water quality parameters is hydrological transport model
. Some of water is diverted to irrigation for agriculture. Rivers
and seas offer opportunity for travel and commerce . Through
erosion , runoff shapes the environment creating river valleys and
deltas which provide rich soil and level ground for the
establishment of population centers. A flood occurs when an area of
land, usually low-lying, is covered with water. It is when a river
overflows its banks or flood from the sea. A drought is an extended
period of months or years when a region notes a deficiency in its
water supply. This occurs when a region receives consistently below
average precipitation.
Fresh water storage
High tide (left) and low tide (right)
Main article: Water resources
Some runoff water is trapped for periods of time, for example in
lakes. At high altitude, during winter, and in the far north and
south, snow collects in ice caps, snow pack and glaciers. Water
also infiltrates the ground and goes into aquifers. This
groundwater later flows back to the surface in springs , or more
spectacularly in hot springs and geysers . Groundwater is also
extracted artificially in wells . This water storage is important,
since clean, fresh water is essential to human and other land-based
life. In many parts of the world, it is in short supply.
Sea water
Main article: Seawater
Sea water contains about 3.5% salt on average, plus smaller amounts
of other substances. The physical properties of sea water differ
from fresh water in some important respects. It freezes at a lower
temperature (about -1.9C) and its density increases with decreasing
temperature to the freezing point, instead of reaching maximum
density at a temperature above freezing. The salinity of water in
major seas varies from about 0.7% in the Baltic Sea to 4.0% in the
Red Sea .
Tides
Main article: Tide
Tides are the cyclic rising and falling of Earth's ocean surface
caused by the tidal forces of the Moon and the Sun acting on the
oceans. Tides cause changes in the depth of the marine and
estuarine water bodies and produce oscillating currents known as
tidal streams. The changing tide produced at a given location is
the result of the changing positions of the Moon and Sun relative
to the Earth coupled with the effects of Earth rotation and the
local bathymetry . The strip of seashore that is submerged at high
tide and exposed at low tide, the intertidal zone , is an important
ecological product of ocean tides.
Effects on life
An oasis is an isolated water source with vegetation in desert
Overview of photosynthesis and respiration . Water (at right),
together with carbon dioxide (CO 2 ), form oxygen and organic
compounds (at left), which can be respired to water and (CO 2
).
From a biological standpoint, water has many distinct properties
that are critical for the proliferation of life that set it apart
from other substances. It carries out this role by allowing organic
compounds to react in ways that ultimately allow replication . All
known forms of life depend on water. Water is vital both as a
solvent in which many of the body's solutes dissolve and as an
essential part of many metabolic processes within the body.
Metabolism is the sum total of anabolism and catabolism. In
anabolism, water is removed from molecules (through energy
requiring enzymatic chemical reactions) in order to grow larger
molecules (e.g. starches, triglycerides and proteins for storage of
fuels and information). In catabolism, water is used to break bonds
in order to generate smaller molecules (e.g. glucose, fatty acids
and amino acids to be used for fuels for energy use or other
purposes). Water is thus essential and central to these metabolic
processes. Therefore, without water, these metabolic processes
would cease to exist, leaving us to muse about what processes would
be in its place, such as gas absorption, dust collection, etc.
Water is also central to photosynthesis and respiration.
Photosynthetic cells use the sun's energy to split off water's
hydrogen from oxygen. Hydrogen is combined with CO 2 (absorbed from
air or water) to form glucose and release oxygen. All living cells
use such fuels and oxidize the hydrogen and carbon to capture the
sun's energy and reform water and CO 2 in the process (cellular
respiration).
Water is also central to acid-base neutrality and enzyme function.
An acid, a hydrogen ion (H + , that is, a proton) donor, can be
neutralized by a base, a proton acceptor such as hydroxide ion (OH
− ) to form water. Water is considered to be neutral, with a
pH (the negative log of the hydrogen ion concentration) of 7. Acids
have pH values less than 7 while bases have values greater than
7.
Some of the biodiversity of a coral reef
Stomach acid (HCl) is useful to digestion. However, its corrosive
effect on the esophagus during reflux can temporarily be
neutralized by ingestion of a base such as aluminum hydroxide to
produce the neutral molecules water and the salt aluminum chloride.
Human biochemistry that involves enzymes usually performs optimally
around a biologically neutral pH of 7.4.
For example, a cell of Escherichia coli contains 70% of water, a
human body 60–70%, plant body up to 90% and the body of an
adult jellyfish is made up of 94–98% water.
Aquatic life forms
Main articles: Hydrobiology and Aquatic plant
Some marine diatoms - a key phytoplankton group
Earth's waters are filled with life. The earliest life forms
appeared in water; nearly all fish live exclusively in water, and
there are many types of marine mammals, such as dolphins and whales
that also live in the water. Some kinds of animals, such as
amphibians , spend portions of their lives in water and portions on
land. Plants such as kelp and algae grow in the water and are the
basis for some underwater ecosystems. Plankton is generally the
foundation of the ocean food chain .
Aquatic animals must obtain oxygen to survive, and they do so in
various ways. Fish have gills instead of lungs , although some
species of fish, such as the lungfish , have both. Marine mammals ,
such as dolphins, whales, otters , and seals need to surface
periodically to breathe air. Smaller life forms are able to absorb
oxygen through their skin.
Effects on human civilization
Water fountain
Civilization has historically flourished around rivers and major
waterways; Mesopotamia , the so-called cradle of civilization, was
situated between the major rivers Tigris and Euphrates ; the
ancient society of the Egyptians depended entirely upon the Nile .
Large metropolises like Rotterdam , London , Montreal , Paris , New
York City , Buenos Aires , Shanghai , Tokyo , Chicago , and Hong
Kong owe their success in part to their easy accessibility via
water and the resultant expansion of trade. Islands with safe water
ports, like Singapore , have flourished for the same reason. In
places such as North Africa and the Middle East , where water is
more scarce, access to clean drinking water was and is a major
factor in human development.
Health and pollution
Environmental Science Program, Iowa State University student
sampling water.
Water fit for human consumption is called drinking water or potable
water . Water that is not potable can be made potable by filtration
or distillation (heating it until it becomes water vapor, and then
capturing the vapor without any of the impurities it leaves
behind), or by other methods (chemical or heat treatment that kills
bacteria). Sometimes the term safe water is applied to potable
water of a lower quality threshold (i.e., it is used effectively
for nutrition in humans that have weak access to water cleaning
processes, and does more good than harm). Water that is not fit for
drinking but is not harmful for humans when used for swimming or
bathing is called by various names other than potable or drinking
water, and is sometimes called safe water , or "safe for bathing".
Chlorine is a skin and mucous membrane irritant that is used to
make water safe for bathing or drinking. Its use is highly
technical and is usually monitored by government regulations
(typically 1 part per million (ppm) for drinking water, and
1–2 ppm of chlorine not yet reacted with impurities for
bathing water).
This natural resource is becoming scarcer in certain places, and
its availability is a major social and economic concern. Currently,
about a billion people around the world routinely drink unhealthy
water. Most countries accepted the goal of halving by 2015 the
number of people worldwide who do not have access to safe water and
sanitation during the 2003 G8 Evian summit . [ 25 ] Even if this
difficult goal is met, it will still leave more than an estimated
half a billion people without access to safe drinking water and
over a billion without access to adequate sanitation. Poor water
quality and bad sanitation are deadly; some five million deaths a
year are caused by polluted drinking water. The World Health
Organization estimates that safe water could prevent 1.4 million
child deaths from diarrhea each year. [ 26 ] Water, however, is not
a finite resource, but rather re-circulated as potable water in
precipitation in quantities many degrees of magnitude higher than
human consumption. Therefore, it is the relatively small quantity
of water in reserve in the earth (about 1% of our drinking water
supply , which is replenished in aquifers around every 1 to 10
years), that is a non-renewable resource, and it is, rather, the
distribution of potable and irrigation water which is scarce,
rather than the actual amount of it that exists on the earth.
Water-poor countries use importation of goods as the primary method
of importing water (to leave enough for local human consumption),
since the manufacturing process uses around 10 to 100 times
products' masses in water.
In the developing world, 90% of all wastewater still goes untreated
into local rivers and streams. [ 27 ] Some 50 countries, with
roughly a third of the world’s population, also suffer from
medium or high water stress, and 17 of these extract more water
annually than is recharged through their natural water cycles. [ 28
] The strain not only affects surface freshwater bodies like rivers
and lakes, but it also degrades groundwater resources.
Human uses
Agriculture
Irrigation of field crops
The most important use of water in agriculture is for irrigation ,
which is a key component to produce enough food. Irrigation takes
up to 90% of water withdrawn in some developing countries [ 29 ]
and significant proportions in more economically developed
countries (United States, 30% of freshwater usage is for
irrigation). [ 30 ]
Water as a scientific standard
On 7 April 1795, the gram was defined in France to be equal to "the
absolute weight of a volume of pure water equal to a cube of one
hundredth of a meter, and to the temperature of the melting ice." [
31 ] For practical purposes though, a metallic reference standard
was required, one thousand times more massive, the kilogram . Work
was therefore commissioned to determine precisely the mass of one
liter of water. In spite of the fact that the decreed definition of
the gram specified water at 0 °C—a highly
reproducible temperature —the scientists chose to redefine
the standard and to perform their measurements at the temperature
of highest water density , which was measured at the time as
4 °C (39 °F). [ 32 ]
The Kelvin temperature scale of the SI system is based on the
triple point of water, defined as exactly 273.16 K or
0.01 °C. The scale is a more accurate development of the
Celsius temperature scale, which was originally defined according
the boiling point (set to 100 °C) and melting point (set
to 0 °C) of water.
Natural water consists mainly of the isotopes hydrogen-1 and
oxygen-16, but there is also small quantity of heavier isotopes
such as hydrogen-2 ( deuterium ). The amount of deuterium oxides or
heavy water is very small, but it still affects the properties of
water. Water from rivers and lakes tends to contain less deuterium
than seawater. Therefore, standard water is defined in the Vienna
Standard Mean Ocean Water specification.
For drinking
Main article: Drinking water
A young girl drinking bottled water
Water quality: fraction of population using improved water sources
by country
The human body is anywhere from 55% to 78% water depending on body
size. [ 33 ] To function properly, the body requires between one
and seven liters of water per day to avoid dehydration ; the
precise amount depends on the level of activity, temperature,
humidity, and other factors. Most of this is ingested through foods
or beverages other than drinking straight water. It is not clear
how much water intake is needed by healthy people, though most
advocates agree that 6–7 glasses of water (approximately 2
liters) daily is the minimum to maintain proper hydration. [ 34 ]
Medical literature favors a lower consumption, typically 1 liter of
water for an average male, excluding extra requirements due to
fluid loss from exercise or warm weather. [ 35 ] For those who have
healthy kidneys, it is rather difficult to drink too much water,
but (especially in warm humid weather and while exercising) it is
dangerous to drink too little. People can drink far more water than
necessary while exercising, however, putting them at risk of water
intoxication (hyperhydration), which can be fatal. The "fact" that
a person should consume eight glasses of water per day cannot be
traced back to a scientific source. [ 36 ] There are other myths
such as the effect of water on weight loss and constipation that
have been dispelled. [ 37 ]
Hazard symbol for No drinking water
An original recommendation for water intake in 1945 by the Food and
Nutrition Board of the National Research Council read: "An ordinary
standard for diverse persons is 1 milliliter for each calorie of
food. Most of this quantity is contained in prepared foods." [ 38 ]
The latest dietary reference intake report by the United States
National Research Council in general recommended (including food
sources): 2.7 liters of water total for women and 3.7 liters for
men. [ 39 ] Specifically, pregnant and breastfeeding women need
additional fluids to stay hydrated. According to the Institute of
Medicine —who recommend that, on average, women consume 2.2
liters and men 3.0 liters—this is recommended to be 2.4
liters (10 cups) for pregnant women and 3 liters (12 cups) for
breastfeeding women since an especially large amount of fluid is
lost during nursing. [ 40 ] Also noted is that normally, about 20%
of water intake comes from food, while the rest comes from drinking
water and beverages ( caffeinated included). Water is excreted from
the body in multiple forms; through urine and faeces , through
sweating , and by exhalation of water vapor in the breath. With
physical exertion and heat exposure, water loss will increase and
daily fluid needs may increase as well.
Humans require water that does not contain too many impurities.
Common impurities include metal salts and oxides (including copper,
iron, calcium and lead) [ 41 ] and/or harmful bacteria , such as
Vibrio . Some solutes are acceptable and even desirable for taste
enhancement and to provide needed electrolytes . [ 42 ]
The single largest freshwater resource suitable for drinking is
Lake Baikal in Siberia, which has a very low salt and calcium
content and is therefore very clean.
Hygiene
The ability of water to make solutions and emulsions is used for
washing. Many industrial processes rely on reactions using
chemicals dissolved in water, suspension of solids in water
slurries or using water to dissolve and extract substances.
Chemical uses
Water is widely used in chemical reactions as a solvent or reactant
and less commonly as a solute or catalyst. In inorganic reactions,
water is a common solvent, dissolving many ionic compounds. In
organic reactions, it is not usually used as a reaction solvent,
because it does not dissolve the reactants well and is amphoteric
(acidic and basic) and nucleophilic . Nevertheless, these
properties are sometimes desirable. Also, acceleration of
Diels-Alder reactions by water has been observed. Supercritical
water has recently been a topic of research. Oxygen-saturated
supercritical water combusts organic pollutants efficiently.
As a heat transfer fluid
Ice used for cooling.
Water and steam are used as heat transfer fluids in diverse heat
exchange systems, due to its availability and high heat capacity,
both as a coolant and for heating. Cool water may even be naturally
available from a lake or the sea. Condensing steam is a
particularly efficient heating fluid because of the large heat of
vaporization. A disadvantage is that water and steam are somewhat
corrosive. In almost all electric power stations , water is the
coolant, which vaporizes and drives steam turbines to drive
generators. In the U.S., cooling power plants is the largest use of
water. [ 30 ]
In the nuclear industry, water can also be used as a neutron
moderator . In a pressurized water reactor , water is both a
coolant and a moderator. This provides a passive safety measure, as
removing the water from the reactor also slows the nuclear reaction
down.
Extinguishing fires
Water is used for fighting wildfires .
Water has a high heat of vaporization and is relatively inert,
which makes it a good fire extinguishing fluid. The evaporation of
water carries heat away from the fire. However, water cannot be
used to fight fires of electric equipment, because impure water is
electrically conductive, or of oils and organic solvents, because
they float on water and the explosive boiling of water tends to
spread the burning liquid.
Use of water in fire fighting should also take into account the
hazards of a steam explosion , which may occur when water is used
on very hot fires in confined spaces, and of a hydrogen explosion,
when substances which react with water, such as certain metals or
hot graphite, decompose the water, producing hydrogen gas .
The power of such explosions was seen in the Chernobyl disaster ,
although the water involved did not come from fire-fighting at that
time but the reactor's own water cooling system. A steam explosion
occurred when the extreme over-heating of the core caused water to
flash into steam. A hydrogen explosion may have occurred as a
result of reaction between steam and hot zirconium .
Recreation
Main article: Water sport (recreation)
Humans use water for many recreational purposes, as well as for
exercising and for sports. Some of these include swimming ,
waterskiing , boating , surfing and diving . In addition, some
sports, like ice hockey and ice skating , are played on ice.
Lakesides, beaches and waterparks are popular places for people to
go to relax and enjoy recreation. Many find the sound and
appearance of flowing water to be calming, and fountains and other
water features in public or private decorations.. Some keep fish
and other life in aquariums or ponds for show, fun, and
companionship. Humans also use water for snow sports i.e. skiing ,
sledding , snowmobiling or snowboarding , which requires the water
to be frozen. People may also use water for play fighting such as
with snowballs , water guns or water balloons .
Water industry
A water-carrier in India , 1882. In many places where running water
was not available, water had to be transported by people.
A manual water pump in China
Water purification facility
Main articles: Water industry and :Category:Water supply and
sanitation by country
The water industry provides drinking water and wastewater services
(including sewage treatment ) to households and industry . Water
supply facilities include water wells cisterns for rainwater
harvesting , water supply network , water purification facilities,
water tanks , water towers , water pipes including old aqueducts .
Atmospheric water generators are in development.
Drinking water is often collected at springs , extracted from
artificial borings (wells) in the ground, or pumped from lakes and
rivers. Building more wells in adequate places is thus a possible
way to produce more water, assuming the aquifers can supply an
adequate flow. Other water sources include rainwater collection.
Water may require purification for human consumption. This may
involve removal of undissolved substances, dissolved substances and
harmful microbes . Popular methods are filtering with sand which
only removes undissolved material, while chlorination and boiling
kill harmful microbes. Distillation does all three functions. More
advanced techniques exist, such as reverse osmosis . Desalination
of abundant seawater is a more expensive solution used in coastal
arid climates .
The distribution of drinking water is done through municipal water
systems , tanker delivery or as bottled water . Governments in many
countries have programs to distribute water to the needy at no
charge. Others argue that the market mechanism and free enterprise
are best to manage this rare resource and to finance the boring of
wells or the construction of dams and reservoirs .
Reducing usage by using drinking (potable) water only for human
consumption is another option. In some cities such as Hong Kong ,
sea water is extensively used for flushing toilets citywide in
order to conserve fresh water resources .
Polluting water may be the biggest single misuse of water; to the
extent that a pollutant limits other uses of the water, it becomes
a waste of the resource, regardless of benefits to the polluter.
Like other types of pollution, this does not enter standard
accounting of market costs, being conceived as externalities for
which the market cannot account. Thus other people pay the price of
water pollution, while the private firms' profits are not
redistributed to the local population victim of this pollution.
Pharmaceuticals consumed by humans often end up in the waterways
and can have detrimental effects on aquatic life if they
bioaccumulate and if they are not biodegradable .
Wastewater facilities are storm sewers and wastewater treatment
plants . Another way to remove pollution from surface runoff water
is bioswale .
Industrial applications
Water is used in power generation . Hydroelectricity is electricity
obtained from hydropower . Hydroelectric power comes from water
driving a water turbine connected to a generator. Hydroelectricity
is a low-cost, non-polluting, renewable energy source. The energy
is supplied by the sun. Heat from the sun evaporates water, which
condenses as rain in higher altitudes, from where it flows
down.
Three Gorges Dam is the largest hydro-electric power station .
Pressurized water is used in water blasting and water jet cutters .
Also, very high pressure water guns are used for precise cutting.
It works very well, is relatively safe, and is not harmful to the
environment. It is also used in the cooling of machinery to prevent
over-heating, or prevent saw blades from over-heating.
Water is also used in many industrial processes and machines, such
as the steam turbine and heat exchanger , in addition to its use as
a chemical solvent . Discharge of untreated water from industrial
uses is pollution . Pollution includes discharged solutes (
chemical pollution ) and discharged coolant water (thermal
pollution). Industry requires pure water for many applications and
utilizes a variety of purification techniques both in water supply
and discharge.
Food processing
Water can be used to cook foods such as noodles .
Water plays many critical roles within the field of food science .
It is important for a food scientist to understand the roles that
water plays within food processing to ensure the success of their
products.
Solutes such as salts and sugars found in water affect the physical
properties of water. The boiling and freezing points of water is
affected by solutes. One mole of sucrose (sugar) per kilogram of
water raises the boiling point of water by 0.51 °C, and one
mole of salt per kg raises the boiling point by 1.02 °C;
similarly, increasing the number of dissolved particles lowers
water's freezing point. [ 43 ] Solutes in water also affect water
activity which affects many chemical reactions and the growth of
microbes in food. [ 44 ] Water activity can be described as a ratio
of the vapor pressure of water in a solution to the vapor pressure
of pure water. [ 43 ] Solutes in water lower water activity. This
is important to know because most bacterial growth ceases at low
levels of water activity. [ 44 ] Not only does microbial growth
affect the safety of food but also the preservation and shelf life
of food.
Water hardness is also a critical factor in food processing. It can
dramatically affect the quality of a product as well as playing a
role in sanitation. Water hardness is classified based on the
amounts of removable calcium carbonate salt it contains per gallon.
Water hardness is measured in grains; 0.064 g calcium carbonate is
equivalent to one grain of hardness. [ 43 ] Water is classified as
soft if it contains 1 to 4 grains, medium if it contains 5 to 10
grains and hard if it contains 11 to 20 grains. [ vague ] [ 43 ]
The hardness of water may be altered or treated by using a chemical
ion exchange system. The hardness of water also affects its pH
balance which plays a critical role in food processing. For
example, hard water prevents successful production of clear
beverages. Water hardness also affects sanitation; with increasing
hardness, there is a loss of effectiveness for its use as a
sanitizer. [ 43 ]
Boiling , steaming , and simmering are popular cooking methods that
often require immersing food in water or its gaseous state, steam.
Water is also used for dishwashing .
Water law, water politics and water crisis
Best estimate of the share of people in developing countries with
access to drinking water 1970–2000
Main articles: Water law , Water right , Water politics , and Water
crisis
See also: Water resources
Water politics is politics affected by water and water resources .
For this reason, water is a strategic resource in the globe and an
important element in many political conflicts. It causes health
impacts and damage to biodiversity.
1.6 billion people have gained access to a safe water source since
1990 [1] . The proportion of people in developing countries with
access to safe water is calculated to have improved from 30% in
1970 [ 4 ] to 71% in 1990, 79% in 2000 and 84% in 2004. This trend
is projected to continue. [ 5 ] To halve, by 2015, the proportion
of people without sustainable access to safe drinking water is one
of the Millennium Development Goals . This goal is projected to be
reached.
A 2006 United Nations report stated that "there is enough water for
everyone", but that access to it is hampered by mismanagement and
corruption. [ 45 ]
The UN World Water Development Report (WWDR, 2003) from the World
Water Assessment Program indicates that, in the next 20 years, the
quantity of water available to everyone is predicted to decrease by
30%. 40% of the world's inhabitants currently have insufficient
fresh water for minimal hygiene . More than 2.2 million people died
in 2000 from waterborne diseases (related to the consumption of
contaminated water) or drought . In 2004, the UK charity WaterAid
reported that a child dies every 15 seconds from easily preventable
water-related diseases; often this means lack of sewage disposal;
see toilet .
Organizations concerned with water protection include International
Water Association (IWA), WaterAid , Water 1st , American Water
Resources Association . Water related conventions are United
Nations Convention to Combat Desertification (UNCCD), International
Convention for the Prevention of Pollution from Ships , United
Nations Convention on the Law of the Sea and Ramsar Convention .
World Day for Water takes place on 22 March and World Ocean Day on
8 June.
Water used in the production of a good or service is virtual water
.
Water in culture
Religion
Main article: Water and religion
Water is considered a purifier in most religions. Major faiths that
incorporate ritual washing ( ablution ) include Christianity ,
Hinduism , Rastafari movement , Islam , Shinto , Taoism , and
Judaism . Immersion (or aspersion or affusion ) of a person in
water is a central sacrament of Christianity (where it is called
baptism ); it is also a part of the practice of other religions,
including Judaism ( mikvah ) and Sikhism ( Amrit Sanskar ). In
addition, a ritual bath in pure water is performed for the dead in
many religions including Judaism and Islam. In Islam, the five
daily prayers can be done in most cases (see Tayammum ) after
completing washing certain parts of the body using clean water (
wudu ). In Shinto, water is used in almost all rituals to cleanse a
person or an area (e.g., in the ritual of misogi ). Water is
mentioned in the Bible 442 times in the New International Version
and 363 times in the King James Version : 2 Peter 3:5(b) states,
"The earth was formed out of water and by water" (NIV). In the
Koran it is stated that "Living things are made of water" and it is
often used to described Paradise.
Philosophy
The Ancient Greek philosopher Empedocles held that water is one of
the four classical elements along with fire , earth and air , and
was regarded as the ylem , or basic substance of the universe.
Water was considered cold and moist. In the theory of the four
bodily humors , water was associated with phlegm . The classical
element of Water was also one of the five elements in traditional
Chinese philosophy , along with earth , fire , wood , and metal
.
Water is also taken as a role model in some parts of traditional
and popular Asian philosophy. James Legge's 1891 translation of the
Dao De Jing states "The highest excellence is like (that of) water.
The excellence of water appears in its benefiting all things, and
in its occupying, without striving (to the contrary), the low place
which all men dislike. Hence (its way) is near to (that of) the
Tao" and "There is nothing in the world more soft and weak than
water, and yet for attacking things that are firm and strong there
is nothing that can take precedence of it—for there is
nothing (so effectual) for which it can be changed." [ 46 ]
Literature
Water is used in literature as a symbol of purification. Examples
include the critical importance of a river in As I Lay Dying by
William Faulkner and the drowning of Ophelia in Hamlet .
Sherlock Holmes held that "From a drop of water, a logician could
infer the possibility of an Atlantic or a Niagara without having
seen or heard of one or the other." [ 47 ]
The New Age (also referred to as the New Age movement , New Age
spirituality , and Cosmic Humanism ) is a decentralized Western
social and spiritual movement that seeks " Universal Truth " and
the attainment of the highest individual human potential . It
includes aspects of Occultism , astrology , esotericism ,
metaphysics , alternative medicine , music , collectivism ,
sustainability , and nature . New Age spirituality is characterized
by an individual approach to spiritual practices and philosophies,
and the rejection of religious doctrine and dogma .
The New Age movement includes elements of older spiritual and
religious traditions ranging from atheism and monotheism through
classical pantheism , naturalistic pantheism , and panentheism to
polytheism combined with science and Gaia philosophy : particularly
archaeoastronomy , astronomy , ecology , environmentalism , the
Gaia hypothesis , psychology , and physics . New Age practices and
philosophies sometimes draw inspiration from major world religions
: Buddhism , Chinese folk religion , Christianity , Hinduism ,
Islam , Judaism ; with particularly strong influences from East
Asian religions , Gnosticism , Neopaganism , New Thought ,
Spiritualism , Theosophy , Universalism , and Western esotericism .
[ 2 ] Additional terms for the movement include All is One [ 3 ]
and Mind-Body-Spirit . [ 1 ]
The modern New Age movement emerged in a distinct form in the late
1960s and early 1970s, although its roots can be traced back to the
19th and early 20th centuries. It gained momentum in the 1980s and
strengthened with the Harmonic Convergence event in 1987. Diverse
individuals from around the world practice New Age spirituality. [
citation needed ]
Contents
1 Movement
1.1 Origins
1.2 Development
1.3 Postmodern
2 Spirituality
2.1 Philosophy and cosmology
2.2 Religion and science
3 Lifestyle
3.1 Demographics
3.2 Holistic health
3.3 Music
3.4 Sustainable living
4 Reception
4.1 Organized religion
4.2 Integral Theory
4.3 Indigenous peoples of the Americas
5 In popular culture
6 See also
7 Notes
8 References
9 Further reading
10 External links
//
Movement
Origins
See also: List of Neopagan movements , List of new religious
movements , and List of religions and spiritual traditions
The term New Age was used as early as 1809 by William Blake who
described a belief in a spiritual and artistic "New Age" in his
preface to Milton: a Poem .
Some of the New Age movement's constituent elements appeared
initially in 19th century metaphysical movements: Spiritualism ,
Theosophy , and New Thought ; also, alternative medicine movements
chiropractic and naturopathy . [ 1 ] [ 3 ] These movements in turn
have roots in Transcendentalism , Mesmerism , Swedenborgianism ,
and various earlier Western esoteric or occult traditions, such as
the hermetic arts of astrology, magic , alchemy , and Kabbalah .
The term New Age was used in this context in Madame Blavatsky 's
book The Secret Doctrine , published in 1888. [ 4 ]
A weekly journal of Christian liberalism and socialism titled The
New Age was published as early as 1894; [ 5 ] it was sold to a
group of socialist writers headed by Alfred Richard Orage and
Holbrook Jackson in 1907. Other historical personalities were
involved: H. G. Wells , George Bernard Shaw , and William Butler
Yeats ; the magazine became a forum for politics , literature , and
the arts . [ 6 ] [ 7 ] Between 1908 and 1914, it was instrumental
in pioneering the British avant-garde from vorticism to imagism .
After 1914, publisher Orage met P. D. Ouspensky , a follower of G.
I. Gurdjieff , and began correspondence with Harry Houdini ,
becoming less interested in literature and art, with an increased
focus on mysticism and other spiritual topics; the magazine was
sold in 1921. According to Brown University , The New Age "...
helped to shape modernism in literature and the arts from 1907 to
1922." [ 8 ]
Development
Popularisation behind these ideas has roots in the work of early
20th century writers such as D. H. Lawrence and William Butler
Yeats . In the early to middle 1900s, American mystic, theologian,
and founder of the Association for Research and Enlightenment Edgar
Cayce was a seminal influence on what later would be termed the New
Age movement ; he was known in particular for the practice some
refer to as channeling . [ 9 ] Former Theosophist Rudolf Steiner
and his Anthroposophical Movement are a major influence.
Neo-Theosophist Alice Bailey published the book Discipleship in the
New Age (1944), which used the term New Age in reference to the
transition from the Astrological Age of Pisces to Aquarius . While
claims of racial bias in the writings of Rudolf Steiner and Alice
Bailey were made, [ 10 ] Steiner emphasized racial equality as a
principle central to anthroposophical thought and humanity 's
progress. [ 11 ] [ 12 ] Any racial elements from these influences
have not remained part of the Anthroposophical Society as
contemporary adherents of the society have either not adopted or
repudiated these beliefs. [ 13 ] [ 14 ] Another early usage of the
term, was by the American artist, mystic, and philosopher Walter
Russell , who spoke of "... this New Age philosophy of the
spiritual re-awakening of man ..." in his essay "Power Through
Knowledge", which was also published in 1944.
Carl Gustav Jung was an early articulator of the concept of the Age
of Aquarius. [ 15 ] In a letter to H. G. Baynes, dated 12 August
1940, he wrote in a passage concerning the destruction of the
temple of Karnak by an earthquake in 26 BC: "1940 is the year when
we approach the meridian of the first star in Aquarius . It is the
premonitory earthquake of the New Age." [ 16 ]
Postmodern
Main article: Postmodernism
A barrel house—the first dwelling constructed at the Findhorn
Ecovillage
The subculture that would later be called New Age already existed
in the early 1970s, based on and adopting ideas originally present
in the counterculture of the 1960s . The Findhorn Foundation
– an intentional community near Findhorn , Moray , Scotland
founded in 1962 – played an instrumental role during the
early growth period of the New Age movement; it continues to
operate the Findhorn Ecovillage .
Widespread use of the term New Age began in the mid 1970s
(reflected in the title of monthly periodical New Age Journal ) and
probably influenced several thousand small metaphysical book and
gift stores that increasingly defined themselves as "New Age
bookstores". [ 17 ] [ 18 ] As a result of the large-scale
activities surrounding the Harmonic Convergence in the mid 1980s
– the term was further popularised by the American mass media
to describe the alternative spiritual subculture – including
practices such as meditation , channeling, crystal healing , astral
projection , psychic experience, holistic health , simple living ,
and environmentalism; or belief in phenomena such as Earth
mysteries , ancient astronauts , extraterrestrial life ,
unidentified flying objects , crop circles , and reincarnation . A
range of New Age publications appeared by the late 1980s such as
Psychic Guide (later renamed Body, Mind & Spirit ), Yoga
Journal , New Age Voice , New Age Retailer , and NAPRA ReView by
the New Age Publishers and Retailers Alliance.
There were several key moments in raising public awareness of this
subculture: the publication of Linda Goodman 's best selling
astrology books Sun Signs (1968) and Love Signs (1978); Hair: The
American Tribal Love-Rock Musical (1967) with the opening song "
Aquarius " and its memorable line " This is the dawning of the Age
of Aquarius " [emphasis added]; the broadcast of Shirley MacLaine
's television mini-series Out on a Limb (1987); and the Harmonic
Convergence (1987) organized by José Argüelles in
Sedona , Arizona . Also influential were the claims of channelers
Jane Roberts (the Seth Material ) and J. Z. Knight ( Ramtha ), as
well as revealed writings A Course in Miracles (1976) by Helen
Schucman , The Celestine Prophecy (1993) by James Redfield , and
Conversations with God (1995) by Neale Donald Walsch . Relevant
works also include the writings of Eckhart Tolle , Barbara Marx
Hubbard , Marianne Williamson , Deepak Chopra , John Holland , Gary
Zukav , and Wayne Dyer ; also, The Secret (2006) by Rhonda Byrne ,
which was based on the writings of Esther Hicks and Jerry Hicks.
A water ionizer is an appliance that ionizes water . Ionized water
is purported to be beneficial to human health and marketed with
claims that it is an antioxidant which can slow aging and prevent
disease. [ 1 ] Others note that such claims contradict basic laws
of chemistry and physiology. [ 2 ]
Contents
1 Ionization
2 Uses
3 See also
4 References
5 External links
//
Ionization
Main article: Electrolysis of water
A water ionizer separates water into alkaline and acid fractions
using a process known as electrolysis . [ 3 ] It does this by
exploiting the electric charge of the calcium and magnesium ions
present in nearly all sources of drinking water. When a source of
water lacks mineral ions, such as distilled water , or has been
filtered by reverse osmosis , water ionization has no effect.
Uses
Some research suggests that alkaline reduced water may be useful in
scavenging free radicals in the laboratory setting. [ 4 ] Tests on
in vitro lymphocytes suggest that reduced water can prevent
hydrogen peroxide -induced damage to DNA , RNA and certain proteins
. [ 5 ] However, drinking ionized water would not be expected to
alter the body's pH , and there is no evidence of any claims made
by manufacturers that drinking ionized water will have a noticeable
effect on the body. [ 2 ]
Electrolyzed water has been used by the food industry to sanitize
food products; though effective in bacterial solutions, it was
found less useful when sanitizing utensils, surfaces and food
products. [ 6 ] [ 7 ] Acidic electrolyzed water (pH 2.3–2.6)
may have use as a seed surface disinfectant or contact bactericide
. [ 8 ]
Water purification is the process of removing undesirable
chemicals, materials, and biological contaminants from raw water.
The goal is to produce water fit for a specific purpose. Most water
is purified for human consumption ( drinking water ) but water
purification may also be designed for a variety of other purposes,
including meeting the requirements of medical, pharmacology,
chemical and industrial applications. In general the methods used
include physical process such as filtration and sedimentation ,
biological processes such as slow sand filters or activated sludge
, chemical process such as flocculation and chlorination and the
use of electromagnetic radiation such as ultraviolet light .
The purification process of water may reduce the concentration of
particulate matter including suspended particles , parasites ,
bacteria , algae , viruses , fungi ; and a range of dissolved and
particulate material derived from the surfaces that water may have
made contact with after falling as rain .
The standards for drinking water quality are typically set by
governments or by international standards. These standards will
typically set minimum and maximum concentrations of contaminants
for the use that is to be made of the water.
It is not possible to tell whether water is of an appropriate
quality by visual examination. Simple procedures such as boiling or
the use of a household activated carbon filter are not sufficient
for treating all the possible contaminants that may be present in
water from an unknown source. Even natural spring water –
considered safe for all practical purposes in the 1800s –
must now be tested before determining what kind of treatment, if
any, is needed. Chemical analysis, while expensive, is the only way
to obtain the information necessary for deciding on the appropriate
method of purification.
According to a 2007 World Health Organization report, 1.1 billion
people lack access to an improved drinking water supply, 88% of the
4 billion annual cases of diarrheal disease are attributed to
unsafe water and inadequate sanitation and hygiene, and 1.8 million
people die from diarrheal diseases each year. The WHO estimates
that 94% of these diarrheal cases are preventable through
modifications to the environment, including access to safe water. [
1 ] Simple techniques for treating water at home, such as
chlorination, filters, and solar disinfection, and storing it in
safe containers could save a huge number of lives each year. [ 2 ]
Reducing deaths from waterborne diseases is a major public health
goal in developing countries.
Control room and schematics of the water purification plant to Lac
de Bret , Switzerland .
Contents
1 Sources of water
2 Treatment
2.1 Pre-treatment
2.1.1 pH adjustment
2.2 Flocculation
2.3 Sedimentation
2.4 Filtration
2.4.1 Slow sand filters
2.4.2 Lava filters
2.4.3 Removal of ions and other dissolved substances
2.4.4 Other mechanical and biological techniques
2.5 Disinfection
2.5.1 Chlorine disinfection
2.6 Chlorine Dioxide Disinfection
2.6.1 Ozone disinfection
2.6.2 Ultraviolet disinfection
2.6.3 Hydrogen peroxide disinfection
2.6.4 Various portable methods of disinfection
2.6.5 Solar water disinfection
2.7 Additional treatment options
3 Other water purification techniques
4 Hydrogen production
5 Safety and controversies
5.1 Demineralized water
6 See also
7 References
8 External links
//
Sources of water
Further information: Water supply
Groundwater : The water emerging from some deep ground water may
have fallen as rain many decades, hundreds, thousands or in some
cases millions of years ago. Soil and rock layers naturally filter
the ground water to a high degree of clarity before it is pumped to
the treatment plant. Such water may emerge as springs, artesian
springs , or may be extracted from boreholes or wells. Deep ground
water is generally of very high bacteriological quality (i.e.,
pathogenic bacteria or the pathogenic protozoa are typically
absent), but the water typically is rich in dissolved solids,
especially carbonates and sulfates of calcium and magnesium .
Depending on the strata through which the water has flowed, other
ions may also be present including chloride , and bicarbonate .
There may be a requirement to reduce the iron or manganese content
of this water to make it pleasant for drinking, cooking, and
laundry use. Disinfection may also be required. Where groundwater
recharge is practised; a process in which river water is injected
into an aquifer to store the water in times of plenty so that it is
available in times of drought; it is equivalent to lowland surface
waters for treatment purposes.
Upland lakes and reservoirs : Typically located in the headwaters
of river systems, upland reservoirs are usually sited above any
human habitation and may be surrounded by a protective zone to
restrict the opportunities for contamination. Bacteria and pathogen
levels are usually low, but some bacteria, protozoa or algae will
be present. Where uplands are forested or peaty, humic acids can
colour the water. Many upland sources have low pH which require
adjustment.
Rivers , canals and low land reservoirs: Low land surface waters
will have a significant bacterial load and may also contain algae,
suspended solids and a variety of dissolved constituents.
Atmospheric water generation is a new technology that can provide
high quality drinking water by extracting water from the air by
cooling the air and thus condensing water vapor.
Rainwater harvesting or fog collection which collects water from
the atmosphere can be used especially in areas with significant dry
seasons and in areas which experience fog even when there is little
rain.
Desalination of seawater by distillation or reverse osmosis .
Treatment
The processes below are the ones commonly used in water
purification plants. Some or most may not be used depending on the
scale of the plant and quality of the water.
Pre-treatment
Pumping and containment - The majority of water must be pumped from
its source or directed into pipes or holding tanks. To avoid adding
contaminants to the water, this physical infrastructure must be
made from appropriate materials and constructed so that accidental
contamination does not occur.
Screening ( see also screen filter ) - The first step in purifying
surface water is to remove large debris such as sticks, leaves,
trash and other large particles which may interfere with subsequent
purification steps. Most deep groundwater does not need screening
before other purification steps.
Storage - Water from rivers may also be stored in bankside
reservoirs for periods between a few days and many months to allow
natural biological purification to take place. This is especially
important if treatment is by slow sand filters . Storage reservoirs
also provide a buffer against short periods of drought or to allow
water supply to be maintained during transitory pollution incidents
in the source river.
Pre-conditioning - Water rich in hardness salts are treated with
soda-ash ( sodium carbonate ) to precipitate calcium carbonate out
utilising the common-ion effect .
Pre-chlorination - In many plants the incoming water was
chlorinated to minimise the growth of fouling organisms on the
pipe-work and tanks. Because of the potential adverse quality
effects (see chlorine below), this has largely been discontinued. [
citation needed ]
Widely varied techniques are available to remove the fine solids,
micro-organisms and some dissolved inorganic and organic materials.
The choice of method will depend on the quality of the water being
treated, the cost of the treatment process and the quality
standards expected of the processed water.
pH adjustment
Distilled water has a pH of 7 (neither alkaline nor acidic) and sea
water has an average pH of 8.3 (slightly alkaline). If the water is
acidic (lower than 7), lime , soda ash , or sodium hydroxide is
added to raise the pH. For somewhat acidic, alkaline waters (lower
than 6.5), forced draft degassifiers are the cheapest way to lower
the pH, as the process raises the pH by stripping dissolved carbon
dioxide (carbonic acid) from the water. Lime is commonly used for
pH adjustment for municipal water, or at the start of a treatment
plant for process water, as it is cheap, but it also increases the
ionic load by raising the water hardness. Making the water slightly
alkaline ensures that coagulation and flocculation processes work
effectively and also helps to minimize the risk of lead being
dissolved from lead pipes and lead solder in pipe fittings. Acid
(HCl or H 2 SO 4 ) may be added to alkaline waters in some
circumstances to lower the pH. Having an alkaline water does not
necessarily mean that lead or copper from the plumbing system will
not be dissolved into the water but as a generality, water with a
pH above 7 is much less likely to dissolve heavy metals than a
water with a pH below 7.
floc floating at the surface of a basin
Mechanical system to push floc out of the water basin
Flocculation
Flocculation is a process which clarifies the water. Clarifying
means removing any turbidity or colour so that the water is clear
and colourless. Clarification is done by causing a precipitate to
form in the water which can be removed using simple physical
methods. Initially the precipitate forms as very small particles
but as the water is gently stirred, these particles stick together
to form bigger particles - this process is sometimes called
flocculation. Many of the small particles that were originally
present in the raw water absorb onto the surface of these small
precipitate particles and so get incorporated into the larger
particles that coagulation produces. In this way the coagulated
precipitate takes most of the suspended matter out of the water and
is then filtered off, generally by passing the mixture through a
coarse sand filter or sometimes through a mixture of sand and
granulated anthracite (high carbon and low volatiles coal).
Coagulants / flocculating agents that may be used include:
Iron (III) hydroxide . This is formed by adding a solution of an
iron (III) compound such as iron(III) chloride to pre-treated water
with a pH of 7 or greater. Iron (III) hydroxide is extremely
insoluble and forms even at a pH as low as 7. Commercial
formulations of iron salts were traditionally marketed in the UK
under the name Cuprus.
Aluminium hydroxide is also widely used as the flocculating
precipitate although there have been concerns about possible health
impacts and mis-handling led to a severe poisoning incident in 1988
at Camelford in south-west UK when the coagulant was introduced
directly into the holding reservoir of final treated water.
PolyDADMAC is an artificially produced polymer and is one of a
class of synthetic polymers that are now widely used. These
polymers have a high molecular weight and form very stable and
readily removed flocs , but tend to be more expensive in use
compared to inorganic materials. The materials can also be
biodegradable.
Sedimentation
Water exiting the flocculation basin may enter the sedimentation
basin , also called a clarifier or settling basin. It is a large
tank with slow flow, allowing floc to settle to the bottom. The
sedimentation basin is best located close to the flocculation basin
so the transit between does not permit settlement or floc break up.
Sedimentation basins can be in the shape of a rectangle, where
water flows from end to end, or circular where flow is from the
centre outward. Sedimentation basin outflow is typically over a
weir so only a thin top layer - furthest from the sediment -
exits.The amount of floc that settles out of the water is dependent
on the time the water spends in the basin and the depth of the
basin. The retention time of the water must therefore be balanced
against the cost of a larger basin. The minimum clarifier retention
time is normally 4 hours. A deep basin will allow more floc to
settle out than a shallow basin. This is because large particles
settle faster than smaller ones, so large particles bump into and
integrate smaller particles as they settle. In effect, large
particles sweep vertically through the basin and clean out smaller
particles on their way to the bottom.
As particles settle to the bottom of the basin, a layer of sludge
is formed on the floor of the tank. This layer of sludge must be
removed and treated. The amount of sludge that is generated is
significant, often 3%-5% of the total volume of water that is
treated. The cost of treating and disposing of the sludge can be a
significant part of the operating cost of a water treatment plant.
The tank may be equipped with mechanical cleaning devices that
continually clean the bottom of the tank or the tank can be taken
out of service when the bottom needs to be cleaned.
Filtration
After separating most floc, the water is filtered as the final step
to remove remaining suspended particles and unsettled floc. The
most common type of filter is a rapid sand filter. Water moves
vertically through sand which often has a layer of activated carbon
or anthracite coal above the sand. The top layer removes organic
compounds, which contribute to taste and odour. The space between
sand particles is larger than the smallest suspended particles, so
simple filtration is not enough. Most particles pass through
surface layers but are trapped in pore spaces or adhere to sand
particles. Effective filtration extends into the depth of the
filter. This property of the filter is key to its operation: if the
top layer of sand were to block all the particles, the filter would
quickly clog.
To clean the filter, water is passed quickly upward through the
filter, opposite the normal direction (called backflushing or
backwashing ) to remove embedded particles. Prior to this,
compressed air may be blown up through the bottom of the filter to
break up the compacted filter media to aid the backwashing process;
this is known as air scouring . This contaminated water can be
disposed of, along with the sludge from the sedimentation basin, or
it can be recycled by mixing with the raw water entering the
plant.
Some water treatment plants employ pressure filters. These work on
the same principle as rapid gravity filters, differing in that the
filter medium is enclosed in a steel vessel and the water is forced
through it under pressure.
Advantages:
Filters out much smaller particles than paper and sand filters
can.
Filters out virtually all particles larger than their specified
pore sizes.
They are quite thin and so liquids flow through them fairly
rapidly.
They are reasonably strong and so can withstand pressure
differences across them of typically 2-5 atmospheres.
They can be cleaned (back flushed) and reused.
Membrane filters are widely used for filtering both drinking water
and sewage (for reuse). For drinking water, membrane filters can
remove virtually all particles larger than
0.2 um—including Giardia and cryptosporidium. Membrane
filters are an effective form of tertiary treatment when it is
desired to reuse the water for industry, for limited domestic
purposes, or before discharging the water into a river that is used
by towns further downstream. They are widely used in industry,
particularly for beverage preparation (including bottled water).
However no filtration can remove substances that are actually
dissolved in the water such as phosphorus, nitrates and heavy metal
ions.
Slow sand filters
Slow "artificial" filtration (a variation of bank filtration ) to
the ground, Water purification plant Káraný, Czech
Republic
Slow sand filters may be used where there is sufficient land and
space as the water must be passed very slowly through the filters.
These filters rely on biological treatment processes for their
action rather than physical filtration. The filters are carefully
constructed using graded layers of sand with the coarsest sand,
along with some gravel, at the bottom and finest sand at the top.
Drains at the base convey treated water away for disinfection.
Filtration depends on the development of a thin biological layer,
called the zoogleal layer or Schmutzdecke , on the surface of the
filter. An effective slow sand filter may remain in service for
many weeks or even months if the pre-treatment is well designed and
produces water with a very low available nutrient level which
physical methods of treatment rarely achieve. Very low nutrient
levels allow water to be safely sent through distribution system
with very low disinfectant levels thereby reducing consumer
irritation over offensive levels of chlorine and chlorine
by-products. Slow sand filters are not backwashed; they are
maintained by having the top layer of sand scraped off when flow is
eventually obstructed by biological growth. [ citation needed ]
A specific 'large-scale' form of slow sand filter is the process of
bank filtration , in which natural sediments in a riverbank are
used to provide a first stage of contaminant filtration. While
typically not sufficiently clean enough to be used directly for
drinking water, the water gained from the associated extraction
wells is much less problematic than river water taken directly from
the major streams where bank filtration is often used.
Lava filters
Lava filters are similar to sand filters and may also only be used
where there is sufficient land and space. Like sand filters, the
filters rely on biological treatment processes for their action
rather than physical filtration. Unlike slow sand filters however,
they are constructed out of 2 layers of lava pebbles and a top
layer of nutrient-free soil (only at the plant roots). On top,
water-purifying plants (such as Iris pseudacorus and Sparganium
erectum ) are placed. Usually, around 1/4 of the dimension of
lavastone is required to purify the water and just like slow sand
filters, a series of herringbone drains are placed (with lava
filters these are placed at the bottom layer). [ 3 ]
Removal of ions and other dissolved substances
Ultrafiltration membranes use polymer membranes with chemically
formed microscopic pores that can be used to filter out dissolved
substances avoiding the use of coagulants. The type of membrane
media determines how much pressure is needed to drive the water
through and what sizes of micro-organisms can be filtered out.
Ion exchange : [ 4 ] [ 5 ] [ 6 ] [ 7 ] [ 8 ] Ion exchange systems
use ion exchange resin - or zeolite -packed columns to replace
unwanted ions. The most common case is water softening consisting
of removal of Ca 2+ and Mg 2+ ions replacing them with benign (soap
friendly) Na + or K + ions. Ion exchange resins are also used to
remove toxic ions such as nitrate , nitrite , lead , mercury ,
arsenic and many others.
Electrodeionization : [ 8 ] [ 4 ] Water is passed between a
positive electrode and a negative electrode. Ion exchange membranes
allow only positive ions to migrate from the treated water toward
the negative electrode and only negative ions toward the positive
electrode. High purity deionized water is produced with a little
worse degree of purification in comparison with ion exchange
treatment. Complete removal of ions from water is regarded as
electrodialysis . The water is often pre-treated with a reverse
osmosis unit to remove non-ionic organic contaminants .
Other mechanical and biological techniques
See also: Greywater and Ecological sanitation
In addition to the many techniques used in large-scale water
treatment, several small-scale, less (or non)-polluting techniques
are also being used to treat polluted water. These techniques
include those based on mechanical and biological processes. An
overview:
mechanical systems: sand filtration , lava filter systems and
systems based on UV -radiation)
biological systems:
plant systems as constructed wetlands and treatment ponds
(sometimes incorrectly called reedbeds and living walls ) and
compact systems as activated sludge systems , biorotors , aerobic
biofilters and anaerobic biofilters , submerged aerated filters ,
and biorolls [ 9 ]
In order to purify the water adequately, several of these systems
are usually combined to work as a whole. Combination of the systems
is done in two to three stages, namely primary and secondary
purification . Sometimes tertiary purification is also added.
Disinfection
Disinfection is accomplished both by filtering out harmful microbes
and also by adding disinfectant chemicals in the last step in
purifying drinking water. Water is disinfected to kill any
pathogens which pass through the filters. Possible pathogens
include viruses , bacteria , including Escherichia coli ,
Campylobacter and Shigella , and protozoa , including Giardia
lamblia and other cryptosporidia . In most developed countries,
public water supplies are required to maintain a residual
disinfecting agent throughout the distribution system, in which
water may remain for days before reaching the consumer. Following
the introduction of any chemical disinfecting agent, the water is
usually held in temporary storage - often called a contact tank or
clear well to allow the disinfecting action to complete.
Chlorine disinfection
Main article: Chlorination
The most common disinfection method involves some form of chlorine
or its compounds such as chloramine or chlorine dioxide . Chlorine
is a strong oxidant that rapidly kills many harmful
micro-organisms. Because chlorine is a toxic gas, there is a danger
of a release associated with its use. This problem is avoided by
the use of sodium hypochlorite , which is a relatively inexpensive
solution that releases free chlorine when dissolved in water.
Chlorine solutions can be generated on site by electrolyzing common
salt solutions. A solid form, calcium hypochlorite exists that
releases chlorine on contact with water. Handling the solid,
however, requires greater routine human contact through opening
bags and pouring than the use of gas cylinders or bleach which are
more easily automated. The generation of liquid sodium hypochlorite
is both inexpensive and safer than the use of gas or solid
chlorine. All forms of chlorine are widely used despite their
respective drawbacks. One drawback is that chlorine from any source
reacts with natural organic compounds in the water to form
potentially harmful chemical by-products trihalomethanes (THMs) and
haloacetic acids (HAAs), both of which are carcinogenic in large
quantities and regulated by the United States Environmental
Protection Agency (EPA) and the Drinking Water Inspectorate in the
UK. The formation of THMs and haloacetic acids may be minimized by
effective removal of as many organics from the water as possible
prior to chlorine addition. Although chlorine is effective in
killing bacteria, it has limited effectiveness against protozoa
that form cysts in water ( Giardia lamblia and Cryptosporidium ,
both of which are pathogenic).
Chlorine Dioxide Disinfection
Chlorine dioxide is a faster-acting disinfectant than elemental
chlorine, however it is relatively rarely used, because in some
circumstances it may create excessive amounts of chlorite, which is
a by-product regulated to low allowable levels in the United States
. Chlorine dioxide is supplied as an aqueous solution and added to
water to avoid gas handling problems; chlorine dioxide gas
accumulations may spontaneously detonate.
The use of chloramine is becoming more common as a disinfectant.
Although chloramine is not as strong an oxidant, it does provide a
longer-lasting residual than free chlorine and it won't form THMs
or haloacetic acids. It is possible to convert chlorine to
chloramine by adding ammonia to the water after addition of
chlorine. The chlorine and ammonia react to form chloramine. Water
distribution systems disinfected with chloramines may experience
nitrification , as ammonia is used a nutrient for bacterial growth,
with nitrates being generated as a by-product.
Ozone disinfection
O 3 is an unstable molecule, a "free radical" of oxygen which
readily gives up one atom of oxygen providing a powerful oxidizing
agent which is toxic to most waterborne organisms. It is a very
strong, broad spectrum disinfectant that is widely used in Europe.
It is an effective method to inactivate harmful protozoa that form
cysts. It also works well against almost all other pathogens. Ozone
is made by passing oxygen through ultraviolet light or a "cold"
electrical discharge. To use ozone as a disinfectant, it must be
created on-site and added to the water by bubble contact. Some of
the advantages of ozone include the production of fewer dangerous
by-products (in comparison to chlorination ) and the lack of taste
and odour produced by ozonation. Although fewer by-products are
formed by ozonation, it has been discovered that the use of ozone
produces a small amount of the suspected carcinogen bromate ,
although little bromine should be present in treated water. Another
of the main disadvantages of ozone is that it leaves no
disinfectant residual in the water. Ozone has been used in drinking
water plants since 1906 where the first industrial ozonation plant
was built in Nice , France . The U.S. Food and Drug Administration
has accepted ozone as being safe; and it is applied as an
anti-microbiological agent for the treatment, storage, and
processing of foods.
Ultraviolet disinfection
Ultraviolet light is very effective at inactivating cysts, as long
as the water has a low level of colour so the UV can pass through
without being absorbed. The main disadvantage to the use of UV
radiation is that, like ozone treatment, it leaves no residual
disinfectant in the water. Because neither ozone nor UV radiation
leaves a residual disinfectant in the water, it is sometimes
necessary to add a residual disinfectant after they are used. This
is often done through the addition of chloramines, discussed above
as a primary disinfectant. When used in this manner, chloramines
provide an effective residual disinfectant with very little of the
negative aspects of chlorination.
Hydrogen peroxide disinfection
Works in a similar way to ozone. Activators such as formic acid are
often added to increase the efficacy of disinfection. It has the
disadvantages that it is slow-working, phytotoxic in high dosage,
and decreases the pH of the water it purifies.
Various portable methods of disinfection
Available for disinfection in emergencies or in remote locations.
Disinfection is the primary goal, since aesthetic considerations
such as taste, odour, appearance, and trace chemical contamination
do not affect the short-term safety of drinking water.
Solar water disinfection
One low-cost method of disinfecting water that can often be
implemented with locally available materials is solar disinfection
(SODIS). [ 10 ] [ 11 ] [ 12 ] [ 13 ] Unlike methods that rely on
firewood , it has low impact on the environment.
One recent study has found that the wild Salmonella which would
reproduce quickly during subsequent dark storage of
solar-disinfected water could be controlled by the addition of just
10 parts per million of hydrogen peroxide . [ 14 ]
Additional treatment options
Water fluoridation : in many areas fluoride is added to water with
the goal of preventing tooth decay . [ 15 ] Fluoride is usually
added after the disinfection process. In the U.S., fluoridation is
usually accomplished by the addition of hexafluorosilicic acid , [
16 ] which decomposes in water, yielding fluoride ions. [ 17 ]
Water conditioning: This is a method of reducing the effects of
hard water. Hardness salts are deposited in water systems subject
to heating because the decomposition of bicarbonate ions creates
carbonate ions that crystallise out of the saturated solution of
calcium or magnesium carbonate. Water with high concentrations of
hardness salts can be treated with soda ash ( sodium carbonate )
which precipitates out the excess salts, through the common-ion
effect , producing calcium carbonate of very high purity. The
precipitated calcium carbonate is traditionally sold to the
manufacturers of toothpaste . Several other methods of industrial
and residential water treatment are claimed (without general
scientific acceptance) to include the use of magnetic or/and
electrical fields reducing the effects of hard water. [ citation
needed ]
Plumbosolvency reduction: In areas with naturally acidic waters of
low conductivity (i.e surface rainfall in upland mountains of
igneous rocks), the water may be capable of dissolving lead from
any lead pipes that it is carried in. The addition of small
quantities of phosphate ion and increasing the pH slightly both
assist in greatly reducing plumbo-solvency by creating insoluble
lead salts on the inner surfaces of the pipes.
Radium Removal: Some groundwater sources contain radium , a
radioactive chemical element. Typical sources include many
groundwater sources north of the Illinois River in Illinois .
Radium can be removed by ion exchange, or by water conditioning.
The back flush or sludge that is produced is, however, a low-level
radioactive waste .
Fluoride Removal: Although fluoride is added to water in many
areas, some areas of the world have excessive levels of natural
fluoride in the source water. Excessive levels can be toxic or
cause undesirable cosmetic effects such as staining of teeth.
Flouride is also a known carcinogen. One method of reducing
fluoride levels is through treatment with activated alumina .
Other water purification techniques
Other popular methods for purifying water, especially for local
private supplies are listed below. In some countries some of these
methods are also used for large scale municipal supplies.
Particularly important are distillation (de-salination of seawater)
and reverse osmosis.
Boiling : Water is heated hot enough and long enough to inactivate
or kill micro-organisms that normally live in water at room
temperature. Near sea level, a vigorous rolling boil for at least
one minute is sufficient. At high altitudes (greater than two
kilometres or 5000 feet) three minutes is recommended. [ 18 ] In
areas where the water is "hard" (that is, containing significant
dissolved calcium salts), boiling decomposes the bicarbonate ions,
resulting in partial precipitation as calcium carbonate . This is
the "fur" that builds up on kettle elements, etc., in hard water
areas. With the exception of calcium, boiling does not remove
solutes of higher boiling point than water and in fact increases
their concentration (due to some water being lost as vapour).
Boiling does not leave a residual disinfectant in the water.
Therefore, water that has been boiled and then stored for any
length of time may have acquired new pathogens.
Granular Activated Carbon filtering: a form of activated carbon
with a high surface area, adsorbs many compounds including many
toxic compounds. Water passing through activated carbon is commonly
used in municipal regions with organic contamination, taste or
odors. Many household water filters and fish tanks use activated
carbon filters to further purify the water. Household filters for
drinking water sometimes contain silver as metallic silver
nanoparticle. if water is held in the carbon block for longer
period, microorganisms can grow inside which results in fouling and
contamination. Silver nanoparticles are excellent anti-bacterial
material and they can decompose toxic halo-organic compounds such
as pesticides into non-toxic organic products.
Distillation involves boiling the water to produce water vapour .
The vapour contacts a cool surface where it condenses as a liquid.
Because the solutes are not normally vaporised, they remain in the
boiling solution. Even distillation does not completely purify
water, because of contaminants with similar boiling points and
droplets of unvapourised liquid carried with the steam. However,
99.9% pure water can be obtained by distillation.
Reverse osmosis : Mechanical pressure is applied to an impure
solution to force pure water through a semi-permeable membrane .
Reverse osmosis is theoretically the most thorough method of large
scale water purification available, although perfect semi-permeable
membranes are difficult to create. Unless membranes are
well-maintained, algae and other life forms can colonize the
membranes.
The use of iron in removing arsenic from water. See Arsenic
contamination of groundwater .
Direct contact membrane distillation (DCMD). Applicable to
desalination. Heated seawater is passed along the surface of a
hydrophobic polymer membrane. Evaporated water passes from the hot
side through pores in the membrane into a stream of cold pure water
on the other side. The difference in vapour pressure between the
hot and cold side helps to push water molecules through.
Gas hydrate crystals centrifuge method. If carbon dioxide gas is
mixed with contaminated water at high pressure and low temperature,
gas hydrate crystals will contain only clean water. This is because
the water molecules bind to the gas molecules at molecule level.
The contaminated water is in liquid form. A centrifuge may be used
to separate the crystals and the concentrated contaminated
water.
Hydrogen production
For the small scale production of hydrogen , water purifiers are
installed to prevent formation of minerals on the surface of the
electrodes and to remove organics and chlorine from utility water.
First, the water passes through a 20 micrometre interference ( mesh
or screen filter ) filter to remove sand and dust particles, then a
charcoal filter using activated carbon to remove organics and
chlorine and finally a de-ionizing filter to remove metallic ions.
Testing can be done before and after the filter to verify the
proper removal of barium , calcium , potassium , magnesium , sodium
and silica .
Another method that is used is reverse osmosis .
Safety and controversies
Drinking water pollution detector Rainbow trout ( Oncorhynchus
mykiss ) is being used in water purification plants to detect acute
water pollution
Accidents have also been known to happen. In April, 2007, the water
supply of Spencer, Massachusetts became contaminated with excess
sodium hydroxide (lye) when its treatment equipment malfunctioned.
[ citation needed ]
Many municipalities have moved from free chlorine to chloramine as
a disinfection agent. However, chloramine in some water systems,
appears to be a corrosive agent. Chloramine can dissolve the
"protective" film inside older service line, with the leaching of
lead into residential spigots. This can result in harmful exposure
to lead , with elevated blood levels of lead the outcome. Lead is a
known neurotoxin . [ 19 ]
Demineralized water
Distillation removes all minerals from water, and the membrane
methods of reverse osmosis and nanofiltration remove most to all
minerals. This results in demineralized water which is not
considered ideal drinking water . The World Health Organization has
investigated the health effects of demineralized water since 1980.
[ 20 ] Experiments in humans found that demineralized water
increased diuresis and the elimination of electrolytes , with
decreased blood serum potassium concentration. Magnesium , calcium
, and other minerals in water can help to protect against
nutritional deficiency. Demineralized water may also increase the
risk from toxic metals because it more readily leaches materials
from piping like lead and cadmium, which is prevented by dissolved
minerals such as calcium and magnesium. Low-mineral water has been
implicated in specific cases of lead poisoning in infants, when
lead from pipes leached at especially high rates into the water.
Recommendations for magnesium have been put at a minimum of
10 mg / L with 20–30 mg/L optimum; for calcium a
20 mg/L minimum and a 40–80 mg/L optimum, and a
total water hardness (adding magnesium and calcium) of 2 to 4
mmol /L. At water hardness above 5 mmol/L, higher incidence of
gallstones, kidney stones, urinary stones, arthrosis, and
arthropathies have been observed. [ 21 ] Additionally, desalination
processes can increase the risk of bacterial contamination. [ 21
]
Manufacturers of home water distillers, of course, claim the
opposite -- that minerals in water are the cause of many diseases,
and that most beneficial minerals come from food, not water. [ 22 ]
[ 23 ] [ 24 ] They quote the American Medical Association as saying
"The body's need for minerals is largely met through foods, not
drinking water." [ 25 ] The WHO report agrees that "drinking water,
with some rare exceptions, is not the major source of essential
elements for humans" and is "not the major source of our calcium
and magnesium intake", yet states that demineralized water is
harmful anyway. "Additional evidence comes from animal experiments
and clinical observations in several countries. Animals given zinc
or magnesium dosed in their drinking water had a significantly
higher concentration of these elements in the serum than animals
given the same elements in much higher amounts with food and
provided with low-mineral water to drink."
A water filter removes impurities from water by means of a fine
physical barrier, a chemical process or a biological process.
Filters cleanse water to various extents for irrigation , drinking
water , aquariums , and swimming pools .
Contents
1 Methods of filtration
2 Types of filters
2.1 Water treatment plant filters
2.2 Point-of-use filters
2.3 Portable water filters
2.4 Homemade water filters
3 Water polishing
4 See also
5 References
//
Methods of filtration
Main article: Filtration
Filters use sieving, adsorption , ion exchanges and other
processes. Unlike a sieve or screen , a filter can remove particles
much smaller than the holes through which the water passes.
Types of filters
Water treatment plant filters
Main article: Water purification
Types of water filters include media filters , screen filters ,
disk filters , slow sand filter beds , rapid sand filters and cloth
filters . [ 1 ]
Point-of-use filters
Point-of-use filters for home use include granular activated carbon
filters (GAC) used for carbon filtering , metallic alloy filters ,
microporous ceramic filters , carbon block resin (CBR) and
ultrafiltration membranes. Some filters use more than one
filtration method. An example of this is a multi-barrier system.
Jug filters can be used for small quantities of drinking water.
Some kettles have built-in filters, primarily to reduce limescale
buildup.
Portable water filters
Main article: Portable water purification
Water filters are used by hikers, by aid organizations during
humanitarian emergencies, and by the military. These filters are
usually small, portable and light (1-2 pounds/0.5-1.0 kg or
less), and usually filter water by working a mechanical hand pump,
although some use a siphon drip system to force water through while
others are built into water bottles. Dirty water is pumped via a
screen-filtered flexible silicon tube through a specialized filter,
ending up in a container. These filters work to remove bacteria ,
protozoa and microbial cysts that can cause disease. Filters may
have fine meshes that must be replaced or cleaned, and ceramic
water filters must have their outside abraded when they have become
clogged with impurities.
These water filters should not be confused with devices or tablets
that are water purifiers , some of which remove or kill viruses
such as hepatitis A and rotavirus .
Homemade water filters
A homemade waterfilter for making drinking water
Water filters can be made on-site using local materials such as
grass, charcoal (e.g. from burned firewood), and sand. These
filters have been used by soldiers and outdoor enthusiasts. [ 2 ]
Due to their low cost they can be made and used by anyone,
including the poor , who often do not have access to safe drinking
water . Regrettably such filters do little if anything to mitigate
against pathogens and other harmful constituents and can give a
false sense of security that the water so produced is potable .
Water polishing
The term water polishing can refer to any process that removes
small (usually microscopic) unwanted material from a portion of
water. The process and its meaning vary from setting to setting: a
manufacturer of aquarium filters may claim that its filters perform
water polishing by capturing "micro particles" within nylon or
polyester pads [ 3 ] just as a chemical engineer can use the term
to refer to the removal of magnetic resins from a solution by
passing the solution over a bed of magnetic particulate. [ 4 ] In
this sense, water polishing is simply another term for water
filtration.
Drinking water or potable water is water of sufficiently high
quality that it can be consumed or used without risk of immediate
or long term harm. In most developed countries , the water supplied
to households, commerce and industry is all of drinking water
standard, even though only a very small proportion is actually
consumed or used in food preparation.
Over large parts of the world, humans have inadequate access to
potable water and use sources contaminated with disease vectors ,
pathogens or unacceptable levels of dissolved chemicals or
suspended solids. Such water is not potable and drinking or using
such water in food preparation leads to widespread acute and
chronic illnesses and is a major cause of death in many countries.
Reduction of waterborne diseases is a major public health goal in
developing countries.
Typically, water supply networks deliver potable water, whether it
is to be used for drinking, washing or landscape irrigation . One
counterexample is urban China , where drinking water can optionally
be delivered by a separate tap.
Contents
1 General
2 Water quality and contaminants
3 Access
4 Requirements
5 Indicators of safe drinking water
6 Diarrhea as a major health effect among children
7 Improving the availability of drinking water
8 In education
9 Drinking water regulation
9.1 European Union
9.2 United States of America
9.2.1 Standard potability testing
10 Bottled water
11 Drinking water preferences of animals
12 See also
13 References
14 External links
//
General
Essential to the survival of all organisms, [ 1 ] water has always
been an important and life-sustaining drink to humans. Excluding
fat , water composes approximately 70% of the human body by mass.
It is a crucial component of metabolic processes and serves as a
solvent for many bodily solutes . Health authorities have
historically suggested at least eight glasses, eight fluid ounces
each (168 ml), of water per day (64 fluid ounces, or 1.89
litres ), [ 2 ] [ 3 ] and the British Dietetic Association
recommends 1.8 litres. [ 1 ] The United States Environmental
Protection Agency has determined that the average adult actually
ingests 2.0 litres per day. [ 3 ]
Spring water , a natural resource from which much bottled water
comes, is generally imbued with minerals. [ 4 ] Tap water ,
delivered by domestic water systems in developed nations , refers
to water piped to homes through a tap . All of these forms of water
are commonly drunk, often purified through filtration . [ 5 ]
Water quality and contaminants
Further information: Water quality and Water
pollution
The examples and perspective in this section may not represent a
worldwide view of the subject . Please improve this article and
discuss the issue on the talk page .
This section requires expansion .
Further information: Appropriate technology#Drinking water
Further information: Drinking water quality in the United
States
Throughout most of the world, the most common contamination of raw
water sources is from human sewage and in particular human faecal
pathogens and parasites. In 2006, waterborne diseases were
estimated to cause 1.8 million deaths each year while about 1.1
billion people lacked proper drinking water. [ 6 ] . It is clear
that people in the developing world need to have access to good
quality water in sufficient quantity, water purification technology
and availability and distribution systems for water. In many parts
of the world the only sources of water are from small streams often
directly contaminated by sewage.
Most water requires some type of treatment before use, even water
from deep wells or springs. The extent of treatment depends on the
source of the water. Appropriate technology options in water
treatment include both community-scale and household-scale
point-of-use (POU) designs. [ 7 ] . A few large urban areas such as
Christchurch . New Zealand have access to sufficiently pure water
of sufficient volume that no treatment of the raw water is
required. [ 8 ]
The most reliable way to kill microbial pathogenic agents is to
heat water to a rolling boil [ 9 ] but this requires abundant
sources of fuel and is very onerous on the households, especially
where it is difficult to store boiled water in sterile conditions.
Other techniques, such as filtration, chemical disinfection, and
exposure to ultraviolet radiation (including solar UV) have been
demonstrated in an array of randomized control trials to
significantly reduce levels of water-borne disease among users in
low-income countries [ 10 ] , but these suffer from the same
problems as boiling methods.
Over the past decade, an increasing number of field-based studies
have been undertaken to determine the success of POU measures in
reducing waterborne disease. The ability of POU options to reduce
disease is a function of both their ability to remove microbial
pathogens if properly applied and such social factors as ease of
use and cultural appropriateness. Technologies may generate more
(or less) health benefit than their lab-based microbial removal
performance would suggest.
The current priority of the proponents of POU treatment is to reach
large numbers of low-income households on a sustainable basis. Few
POU measures have reached significant scale thus far, but efforts
to promote and commercially distribute these products to the
world's poor have only been under way for a few years.
Parameters for drinking water quality typically fall under two
categories: chemical/physical and microbiological.
Chemical/physical parameters include heavy metals , trace organic
compounds , total suspended solids (TSS), and turbidity .
Microbiological parameters include Coliform bacteria , E. coli ,
and specific pathogenic species of bacteria (such as cholera
-causing Vibrio cholerae ), viruses , and protozoan parasites .
Chemical parameters tend to pose more of a chronic health risk
through buildup of heavy metals although some components like
nitrates/nitrites and arsenic may have a more immediate impact.
Physical parameters affect the aesthetics and taste of the drinking
water and may complicate the removal of microbial pathogens.
Originally, fecal contamination was determined with the presence of
coliform bacteria , a convenient marker for a class of harmful
fecal pathogens . The presence of fecal coliforms (like E. Coli )
serves as an indication of contamination by sewage . Additional
contaminants include protozoan oocysts such as Cryptosporidium sp.
, Giardia lamblia , Legionella , and viruses (enteric). [ 11 ]
Microbial pathogenic parameters are typically of greatest concern
because of their immediate health risk.
Access
Further information: Water resources
Only forty-six percent of people in Africa have safe drinking
water.
Drinking water vending machines in Thailand . One litre of purified
water is sold (into the customer's own bottle) for 1 baht .
Shipot, a common source of drinking water in a Ukrainian
village.
Water quality - percent of population using improved water sources
by country
70% of the Earth's surface is covered by water. Water is available
almost everywhere if proper methods are used to get it. Sources
where water may be obtained include:
ground sources such as groundwater , hyporheic zones and aquifers
.
precipitation which includes rain, hail, snow, fog, etc.
surface water such as rivers, streams, glaciers
biological sources such as plants.
the sea through desalination
Access to drinkable water is a complicated, yet vital issue. There
is great diversity in access not only between countries but within
countries and even cities.
Cost is the major limiting factor of access to drinkable water.
The most efficient way to transport and deliver potable water is
through pipes. However, this requires a enormous up front
infrastructure costs. Further the high continual operating costs
mean many systems fall into disrepair in both developed and
undeveloped countries. The cost to replace the deteriorating water
and sanitation infrastructure of industrialized countries may be as
high as $200 billion a year. Further, Leakage of pipes reduces
access to water. Leakage rates of 50% are not uncommon in urban
systems [ 12 ]
Because of the high initial investments, many debt impoverished
nations cannot afford to develop this infrastructure. So people in
these areas end up paying a much higher percentage of their income
on water. [ 13 ] 2003 statistics from El Salvador, for example,
indicate that the poorest 20% of households spend more than 10% of
their total income on water. In the United Kingdom authorities
define spending of more than 3% of one's income on water as a
hardship. [ 14 ]
The Millennium Development Goal of halving the proportion of people
without access to safe drinking water between 1990 and 2015 will
probably be reached. Although some countries still face enormous
challenges. [ 15 ]
Rural communities are the furthest from meeting the 2015 MDGs
drinking water target. Globally only 27% of the rural population
has water piped directly to their home and 24% rely on unimproved
sources. Of the 884 million people without access to an improved
water source, 746 million people (84%) live in rural areas.
Sub-Saharan Africa has made the least progress in improved water
sources since 1990, improving only 9% to 2006. In contrast, the
Eastern Asian region saw a dramatic drop from 45% to 9% reliance on
unimproved water in the same time period. [ 16 ]
Table 2: Percentage of population with access to safe drinking
water (2000) [ 17 ]
Country
%
Country
%
Country
%
Country
%
Country
%
Albania
97
Algeria
89
Azerbaijan
78
Brazil
87
Chile
93
China
75
Cuba
91
Egypt
97
India
84
Indonesia
78
Iran
92
Iraq
85
Kenya
57
Mexico
88
Morocco
80
Peru
80
Philippines
86
South Africa
86
South Korea
92
Sudan
67
Syria
80
Turkey
82
Uganda
52
Venezuela
83
Zimbabwe
83
Note: All industrialized countries (as listed by UNICEF) with data
available are at 100%.
In the U.S, the typical nonconserving single family home uses 69.3
gallons of water per capita per day. In some parts of the country
there are water supplies that are dangerously low due to drought,
particularly in the West and the South East region of the U.S. [ 18
] .
Requirements
Main article: Fluid balance
Water is necessary for most life on Earth. Humans can survive for
several weeks without food, but for only a few days without water.
The exact amount of water a human needs is highly individual, as it
depends on the condition of the subject, the amount of physical
exercise, and on the environmental temperature and humidity. [ 19 ]
In the US, the reference daily intake (RDI) for water is 3.7 litres
per day for human males older than 18, and 2.7 litres for human
females older than 18 [ 20 ] including water contained in food,
beverages, and drinking water. It is a common misconception that
everyone should drink two litres (68 ounces, or about eight 8-oz
glasses) of water per day and is not supported by scientific
research. Various reviews of all the scientific literature on the
topic performed in 2002 and 2008 could not find any solid
scientific evidence that recommended drinking eight glasses of
water per day. [ 21 ] [ 22 ] [ 23 ] For example, people in hotter
climates will require greater water intake than those in cooler
climates. An individual's thirst provides a better guide for how
much water they require rather than a specific, fixed number. A
more flexible guideline is that a normal person should urinate 4
times per day, and the urine should be a light yellow color.
A constant supply is needed to replenish the fluids lost through
normal physiological activities, such as respiration, perspiration
and urination . Food contributes 0.5 to 1 litre, and the metabolism
of protein , fat , and carbohydrates produces another 0.25 to 0.4
litres [ 24 ] , which means that 2 to 3 litres of water for men and
1 to 2 litres of water for women should be taken in as fluid in
order to meet the RDI. In terms of mineral nutrients intake, it is
unclear what the drinking water contribution is. However, inorganic
minerals generally enter surface water and ground water via storm
water runoff or through the Earth's crust. Treatment processes also
lead to the presence of some mineral nutrients. Examples include
fluoride , calcium , zinc , manganese , phosphate , and sodium
compounds. [ 25 ] Water generated from the biochemical metabolism
of nutrients provides a significant proportion of the daily water
requirements for some arthropods and desert animals, but provides
only a small fraction of a human's necessary intake. There are a
variety of trace elements present in virtually all potable water,
some of which play a role in metabolism. For example sodium,
potassium and chloride are common chemicals found in small
quantities in most waters, and these elements play a role (not
necessarily major) in body metabolism. Other elements such as
fluoride, while beneficial in low concentrations, can cause dental
problems and other issues when present at high levels. Water is
essential for the growth and maintenance of our bodies, as it is
involved in a number of biological processes.
Profuse sweating can increase the need for electrolyte (salt)
replacement. Water intoxication (which results in hyponatremia ),
the process of consuming too much water too quickly, can be
fatal.
The human kidneys will normally adjust to varying levels of water
intake. The kidneys will require time to adjust to the new water
intake level. This can cause someone who drinks a lot of water to
become dehydrated more easily than someone who routinely drinks
less. Survival classes recommend that someone who expects to be in
an environment with little water (such as a desert), not to drink
water excessively, but rather to drink gradually decreasing amounts
for several days before their trip to accustom the kidneys to
making concentrated urine. Not using this method can, and has been
known to be fatal. [ 26 ]
Indicators of safe drinking water
Access to safe drinking water is indicated by the number of people
using proper sanitary sources. These improved drinking water
sources include household connection, public standpipe , borehole
condition, protected dug well, protected spring, and rain water
collection. Sources that don't encourage improved drinking water to
the same extent as previously mentioned include: unprotected well,
unprotected spring, rivers or ponds, vender-provided water, bottled
water (consequential of limitations in quantity, not quality of
water), and tanker truck water. Access to sanitary water comes hand
in hand with access to improved sanitation facilities for excreta.
These facilities include connection to public sewer, connection to
septic system, pour-flush latrine , and ventilated improved pit
latrine . Unimproved sanitation facilities are: public or shared
latrine, open pit latrine, or bucket latrine [ 27 ] .
Diarrhea as a major health effect among children
Diarrheal diseases cause ninety percent of all deaths of children
under five years old in developing countries. Malnutrition ,
especially protein-energy malnutrition , can decrease the
children's resistance to infections, including water-related
diarrheal diseases. In 2000-2003, 769,000 children under five years
old in sub-Saharan Africa died each year from diarrheal diseases.
As a result of only thirty-six percent of the population in the
sub-Saharan region having access to proper means of sanitation,
more than 2000 childrens' lives are lost every day. In South Asia,
683,000 children under five years old died each year from diarrheal
disease from 2000-2003. During the same time period, in developed
countries, 700 children under five years old died from diarrheal
disease. Improved water supply reduces diarrhea morbidity by
twenty-five percent and improvements in drinking water through
proper storage in the home and chlorination reduces diarrhea
episodes by thirty-nine percent. [ 28 ]
Improving the availability of drinking water
One of the Millennium Development Goals (MDGs) set by the UN
includes environmental sustainability. In 2004, only forty-two
percent of people in rural areas had access to clean water. [ 29 ]
.
Solar water disinfection is a low-cost method of purifying water
that can often be implemented with locally available materials. [
30 ] [ 31 ] [ 32 ] [ 33 ] Unlike methods that rely on firewood , it
has low impact on the environment.
One program developed to help people gain access to safe drinking
water is the Water Aid program. Working in 17 countries to help
provide water, Water Aid international is helping the sanitation
and hygiene education to some of the world's poorest people.
[10]
The Global Framework for Action (GF4A) is a organization that
brings together stakeholders, national governments, donors and NGOs
(such as Water aid) to define manageable targets and deadlines. 23
Countries are off-track to meet the MDG goals for improved water
availability. [ 34 ]
However, not all efforts to increase availability of safe drinking
water have been effective, and some have been damaging. The 1980s
was declared the International Decade of water by the UN. However,
the assumption was made that groundwater is inherently safer than
water from rivers, ponds and canals. While instances of cholera,
typhoid and diarrhea were reduced toxic level of fluoride were
found. Borehole wells were either not tested or not tested
thoroughly. Fluoride slowly dissolved from the granite rocks
underneath India and slowly poisoned the population, particularly
evident in the bone deformations of children. [ 35 ] . Further, in
Bangladesh, it is estimated that half of the countries 12 million
tube wells have unacceptable levels of arsenic due to the wells not
being dug deep enough (past 100 M). The Bangladeshi government had
spent less than $7 million of the 34 million allocated for solving
the problem by the World Bank in 1998. [ 36 ] [ 37 ] . Natural
arsenic poisoning is a global threat, 140 million people affected
in 70 countries on all continents. [ 38 ] These examples illustrate
the need to examine each location on a case by case basis and not
assume what works in one area will work in another.
In education
In Britain, many schools have poor provision of drinking water to
pupils through the day. Studies have been made upon the effect of
increasing the provision of water and significant improvements in
test scores have been observed. Areas such as Brighton have
introduced a Schools Water Policy to ensure an adequate intake of
1.5 to 1.75 litres for 5-10 year olds. [ 39 ]
Drinking water regulation
The examples and perspective in this section may not represent a
worldwide view of the subject . Please improve this article and
discuss the issue on the talk page .
European Union
The EU sets legislation on drinking water quality in addition to
factors such as how, where and when water can be extracted from the
environment. Directive 2000/60/EC of the European Parliament and of
the Council of 23 October 2000 establishing a framework for
Community action in the field of water policy , known as the water
framework directive , is the primary piece of legislation governing
drinking water. [ 40 ]
Each member state is responsible for establishing the required
policing measures to ensure that the legislation is implemented.
For example, in the UK the Drinking Water Inspectorate polices the
water companies.
United States of America
Main article: Drinking water quality in the United States
In the United States , the Environmental Protection Agency (EPA)
sets standards for tap and public water systems under the Safe
Drinking Water Act (SDWA). [ 41 ] The Food and Drug Administration
(FDA) regulates bottled water as a food product under the Federal
Food, Drug, and Cosmetic Act (FFDCA). [ 42 ] Bottled water is not
necessarily more pure, or more tested, than public tap water . [ 43
] However, there is evidence that the United States federal
regulations of drinking water do not ensure safe water, as some of
the regulations have not been updated with more recent science. Dr.
Peter W. Pruess, who became the head of the U.S. EPA's division
analyzing environmental risks in 2004, has been "particularly
concerned", and has faced controversy in studies which suggest that
regulations against certain chemicals should be tightened. [ 44
]
Standard potability testing
A standard testing of water's potability consists of drawing a
sample from a known property or water source, providing State
Certified Nitrate/Nitrogen and Coliform Bacteria Testing, along
with E.Coli testing (FHA/VA). It also means providing testing for
Total Dissolved Solids, Water Hardness, pH, and Iron Content
Testing. A Certified Laboratory must provide proper operation of
all Water Softening and Filtration Systems, and provide written
results of the above testing with a standarized time frame (2 weeks
general).
Bottled water
Main article: Bottled water
Drinking water of a variety of qualities is bottled and sold for
public consumption throughout the world. Trends in sales and
consumption of bottled water have risen significantly in the last
two decades in both developed and developing countries.
Drinking pigeon
Drinking water preferences of animals
The qualitative and quantitative aspects of drinking water
requirements of domesticated animals are studied and described
within the context of animal husbandry . However, relatively few
studies have been focused on the drinking behavior of wild animals.
A recent study has shown, e.g., that feral pigeons do not
discriminate drinking water according to its content of methabolic
wastes, such as uric acid or urea (mimicing faeces- or
urine-pollution by birds or mammals respectively). [ 45 ]
In chemistry , an alkali (from Arabic : Al-Qaly
القلي,
القالي ) is a basic , ionic
salt of an alkali metal or alkaline earth metal element . Alkalis
are best known for being bases that dissolve in water . Bases are
compounds with a pH greater than 7. The adjective alkaline is
commonly used in English as a synonym for base, especially for
soluble bases. This broad use of the term is likely to have come
about because alkalis were the first bases known to obey the
Arrhenius definition of a base and are still among the more common
bases. Since Brønsted-Lowry acid-base theory , the term
alkali in chemistry is normally restricted to those salts
containing alkali and alkaline earth metal elements.
Contents
1 Etymology
2 Common properties
3 Confusion between alkali and base
4 Salts
5 Alkaline soil
6 Lakes
7 References
//
Etymology
The word "alkali" is derived from Arabic al qalīy = the
calcined ashes , referring to the original source of alkaline
substance. Ashes were used in conjunction with animal fat to
produce soap , a process known as saponification .
Common properties
Alkalis are all Arrhenius bases, which form hydroxide ions (OH - )
when dissolved in water. Common properties of alkaline aqueous
solutions include:
Moderately-concentrated solutions (over 10 −3 M) have a pH of
7.1 or greater. This means that they will turn phenolphthalein from
colorless to pink.
Concentrated solutions are caustic (causing chemical burns).
Alkaline solutions are slippery or soapy to the touch, due to the
saponification of the fatty acids on the surface of the skin.
Alkalis are normally water soluble , although some like barium
carbonate are only soluble when reacting with an acidic aqueous
solution.
Acids and alkalis are measured on a pH scale
Alkalis are commonly found in household cleaners and toothpaste
Confusion between alkali and base
The terms "base" and "alkali" are often used interchangeably,
particularly outside of a scientific context, but they do not have
the same meaning. While all alkaline solutions are basic, not all
bases are alkaline. The following are common mistakes:
The phrase "measuring the alkalinity of soil" is incorrect since
the property measured is actually the pH (base property).
Calling bases that are not alkalis, such as ammonia , alkaline
(ammonia is a base but not an alkali).
Also, not all salts formed by alkali metals are alkaline; this
designation applies only to those salts that are basic. And while
most electropositive metal oxides are basic, only the soluble
alkali metal and alkaline earth metal oxides can be correctly
called alkalis.
This definition of an alkali as a basic salt of an alkali metal or
alkaline earth metal is the most common, based on dictionary
definitions [1] [2] , however conflicting definitions of the term
alkali do exist. These include:
Any base that is water-soluble and forms hydroxide ions [3] [4] .
In chemistry, this is more accurately called an Arrhenius base
.
The solution of a base in water [5] . This would be an Arrhenius
base in solution.
Name given by chemists to an important group of subtances, the
behaviour of bases the main alkali are 1,the hydroxides potassium
2,
Salts
Most basic salts are alkali salts, of which common examples
are:
sodium hydroxide (often called "caustic soda")
potassium hydroxide (commonly called "caustic potash")
lye (generic term, for either of the previous two, or even for a
mixture)
calcium carbonate (sometimes called "free lime")
magnesium hydroxide is an example of an atypical alkali since it
has low solubility in water (although the dissolved portion is
considered a strong base due to complete dissociation of its
ions).
Alkaline soil
Soil with a pH value higher than 7.3 is normally referred to as
alkaline. This soil property can occur naturally, due to the
presence of alkali salts. Although some plants do prefer slightly
basic soil (including vegetables like cabbage and fodder like
buffalograss ), most plants prefer a mildly acidic soil (pH between
6.0 and 6.8), and alkaline soils can cause problems.
Lakes
In alkali lakes (a type of salt lake ), evaporation concentrates
the naturally-occurring alkali salts, often forming a crust of
mildly-basic salt across a large area.
Examples of alkali lakes:
Redberry Lake, Saskatchewan , Canada .
Tramping Lake, Saskatchewan , Canada.
Mono lake , California , United States
Summer Lake , Oregon , United States
Alkali Lake, British Columbia and the adjoining reserves of the
Alkali Lake Indian Band are named for a local Alkali Lake, which
got its name from a large patch of alkali on the hillside above the
lake, which is not itself alkali, [ 1 ] although there are many in
the Cariboo district and adjoining regions of the British Columbia
Interior .
In chemistry , an alkali (from Arabic : Al-Qaly
القلي,
القالي ) is a basic , ionic
salt of an alkali metal or alkaline earth metal element . Alkalis
are best known for being bases that dissolve in water . Bases are
compounds with a pH greater than 7. The adjective alkaline is
commonly used in English as a synonym for base, especially for
soluble bases. This broad use of the term is likely to have come
about because alkalis were the first bases known to obey the
Arrhenius definition of a base and are still among the more common
bases. Since Brønsted-Lowry acid-base theory , the term
alkali in chemistry is normally restricted to those salts
containing alkali and alkaline earth metal elements.
Contents
1 Etymology
2 Common properties
3 Confusion between alkali and base
4 Salts
5 Alkaline soil
6 Lakes
7 References
//
Etymology
The word "alkali" is derived from Arabic al qalīy = the
calcined ashes , referring to the original source of alkaline
substance. Ashes were used in conjunction with animal fat to
produce soap , a process known as saponification .
Common properties
Alkalis are all Arrhenius bases, which form hydroxide ions (OH - )
when dissolved in water. Common properties of alkaline aqueous
solutions include:
Moderately-concentrated solutions (over 10 −3 M) have a pH of
7.1 or greater. This means that they will turn phenolphthalein from
colorless to pink.
Concentrated solutions are caustic (causing chemical burns).
Alkaline solutions are slippery or soapy to the touch, due to the
saponification of the fatty acids on the surface of the skin.
Alkalis are normally water soluble , although some like barium
carbonate are only soluble when reacting with an acidic aqueous
solution.
Acids and alkalis are measured on a pH scale
Alkalis are commonly found in household cleaners and toothpaste
Confusion between alkali and base
The terms "base" and "alkali" are often used interchangeably,
particularly outside of a scientific context, but they do not have
the same meaning. While all alkaline solutions are basic, not all
bases are alkaline. The following are common mistakes:
The phrase "measuring the alkalinity of soil" is incorrect since
the property measured is actually the pH (base property).
Calling bases that are not alkalis, such as ammonia , alkaline
(ammonia is a base but not an alkali).
Also, not all salts formed by alkali metals are alkaline; this
designation applies only to those salts that are basic. And while
most electropositive metal oxides are basic, only the soluble
alkali metal and alkaline earth metal oxides can be correctly
called alkalis.
This definition of an alkali as a basic salt of an alkali metal or
alkaline earth metal is the most common, based on dictionary
definitions [1] [2] , however conflicting definitions of the term
alkali do exist. These include:
Any base that is water-soluble and forms hydroxide ions [3] [4] .
In chemistry, this is more accurately called an Arrhenius base
.
The solution of a base in water [5] . This would be an Arrhenius
base in solution.
Name given by chemists to an important group of subtances, the
behaviour of bases the main alkali are 1,the hydroxides potassium
2,
Salts
Most basic salts are alkali salts, of which common examples
are:
sodium hydroxide (often called "caustic soda")
potassium hydroxide (commonly called "caustic potash")
lye (generic term, for either of the previous two, or even for a
mixture)
calcium carbonate (sometimes called "free lime")
magnesium hydroxide is an example of an atypical alkali since it
has low solubility in water (although the dissolved portion is
considered a strong base due to complete dissociation of its
ions).
Alkaline soil
Soil with a pH value higher than 7.3 is normally referred to as
alkaline. This soil property can occur naturally, due to the
presence of alkali salts. Although some plants do prefer slightly
basic soil (including vegetables like cabbage and fodder like
buffalograss ), most plants prefer a mildly acidic soil (pH between
6.0 and 6.8), and alkaline soils can cause problems.
Lakes
In alkali lakes (a type of salt lake ), evaporation concentrates
the naturally-occurring alkali salts, often forming a crust of
mildly-basic salt across a large area.
Examples of alkali lakes:
Redberry Lake, Saskatchewan , Canada .
Tramping Lake, Saskatchewan , Canada.
Mono lake , California , United States
Summer Lake , Oregon , United States
Alkali Lake, British Columbia and the adjoining reserves of the
Alkali Lake Indian Band are named for a local Alkali Lake, which
got its name from a large patch of alkali on the hillside above the
lake, which is not itself alkali, [ 1 ] although there are many in
the Cariboo district and adjoining regions of the British Columbia
Interior .
In typical usage, water refers only to its liquid form or state ,
but the substance also has a solid state, ice , and a gaseous
state, water vapor or steam . Water covers 71% of the Earth 's
surface [ 2 ] . On Earth, it is found mostly in oceans and other
large water bodies, with 1.6% of water below ground in aquifers and
0.001% in the air as vapor , clouds (formed of solid and liquid
water particles suspended in air), and precipitation . [ 3 ] Oceans
hold 97% of surface water, glaciers and polar ice caps 2.4%, and
other land surface water such as rivers , lakes and ponds 0.6%. A
very small amount of the Earth's water is contained within
biological bodies and manufactured products.
Water on Earth moves continually through a cycle of evaporation or
transpiration ( evapotranspiration ), precipitation , and runoff ,
usually reaching the sea . Over land, evaporation and transpiration
contribute to the precipitation over land.
Clean, fresh drinking water is essential to human and other
lifeforms. Access to safe drinking water has improved steadily and
substantially over the last decades in almost every part of the
world. [ 4 ] [ 5 ] There is a clear correlation between access to
safe water and GDP per capita. [ 6 ] However, some observers have
estimated that by 2025 more than half of the world population will
be facing water-based vulnerability. [ 7 ] A recent report
(November 2009) suggests that by 2030, in some developing regions
of the world, water demand will exceed supply by 50%. [ 8 ] Water
plays an important role in the world economy , as it functions as a
solvent for a wide variety of chemical substances and facilitates
industrial cooling and transportation. Approximately 70% of
freshwater is consumed by agriculture . [ 9 ]
Contents
1 Chemical and physical properties
2 Taste and odor
3 Distribution of water in nature
3.1 Water in the universe
3.2 Water and habitable zone
4 Water on Earth
4.1 Water cycle
4.2 Fresh water storage
4.3 Sea water
4.4 Tides
5 Effects on life
5.1 Aquatic life forms
6 Effects on human civilization
6.1 Health and pollution
6.2 Human uses
6.2.1 Agriculture
6.2.2 Water as a scientific standard
6.2.3 For drinking
6.2.4 Hygiene
6.2.5 Chemical uses
6.2.6 As a heat transfer fluid
6.2.7 Extinguishing fires
6.2.8 Recreation
6.2.9 Water industry
6.2.10 Industrial applications
6.2.11 Food processing
7 Water law, water politics and water crisis
8 Water in culture
8.1 Religion
8.2 Philosophy
8.3 Literature
9 See also
9.1 Other topics
10 References
11 Further reading
11.1 Water as a natural resource
12 External links
//
Chemical and physical properties
Main articles: Water (properties) , Water (data page) , and Water
model
Model of hydrogen bonds between molecules of water
Impact from a water drop causes an upward "rebound" jet surrounded
by circular capillary waves .
Snowflakes by Wilson Bentley , 1902
Dew drops adhering to a spider web
Capillary action of water compared to mercury
Water is the chemical substance with chemical formula H 2 O : one
molecule of water has two hydrogen atoms covalently bonded to a
single oxygen atom.
Water appears in nature in all three common states of matter and
may take many different forms on Earth: water vapor and clouds in
the sky; seawater and icebergs in the polar oceans; glaciers and
rivers in the mountains ; and the liquid in aquifers in the
ground.
The major chemical and physical properties of water are:
Water is a tasteless, odorless liquid at standard temperature and
pressure . The color of water and ice is, intrinsically, a very
light blue hue, although water appears colorless in small
quantities. Ice also appears colorless, and water vapor is
essentially invisible as a gas. [ 10 ]
Water is transparent , and thus aquatic plants can live within the
water because sunlight can reach them. Only strong UV light is
slightly absorbed .
Since the water molecule is not linear and the oxygen atom has a
higher electronegativity than hydrogen atoms, it carries a slight
negative charge, whereas the hydrogen atoms are slightly positive.
As a result, water is a polar molecule with an electrical dipole
moment . The net interactions between the dipoles on each molecule
cause an effective skin effect at the interface of water with other
substances, or air at the surface, the latter given rise to water's
high surface tension . This dipolar nature contributes to water
molecules' tendency to form hydrogen bonds which cause water's many
special properties. [ 11 ] The polar nature also favors adhesion to
other materials.
Each hydrogen nucleus is bound to the central oxygen atom by a pair
of electrons that are shared between them; chemists call this
shared electron pair a covalent chemical bond. In H 2 O, only two
of the six outer-shell electrons of oxygen are used for this
purpose, leaving four electrons which are organized into two
non-bonding pairs. The four electron pairs surrounding the oxygen
tend to arrange themselves as far from each other as possible in
order to minimize repulsions between these clouds of negative
charge. This would ordinarily result in a tetrahedral geometry in
which the angle between electron pairs (and therefore the H-O-H
bond angle) is 109.5°. However, because the two non-bonding
pairs remain closer to the oxygen atom, these exert a stronger
repulsion against the two covalent bonding pairs, effectively
pushing the two hydrogen atoms closer together. The result is a
distorted tetrahedral arrangement in which the H-O-H angle is
104.5°. [ 12 ]
A result of interplay of these properties, Capillary action refers
to the tendency of water to move up a narrow tube against the force
of gravity . This property is relied upon by all vascular plants ,
such as trees.
Water is a good solvent and is often referred to as the universal
solvent . Substances that dissolve in water, e.g., salts , sugars ,
acids , alkalis , and some gases – especially oxygen, carbon
dioxide ( carbonation ) are known as hydrophilic (water-loving)
substances, while those that do not mix well with water (e.g., fats
and oils ), are known as hydrophobic (water-fearing)
substances.
All the major components in cells ( proteins , DNA and
polysaccharides ) are also dissolved in water.
Pure water has a low electrical conductivity , but this increases
significantly with the dissolution of a small amount of ionic
material such as sodium chloride .
The boiling point of water (and all other liquids) is dependent on
the barometric pressure . For example, on the top of Mt. Everest
water boils at about 68 °C (154 °F), compared to
100 °C (212 °F) at sea level . Conversely, water
deep in the ocean near geothermal vents can reach temperatures of
hundreds of degrees and remain liquid.
Water has the second highest specific heat capacity of any known
substance, after ammonia , as well as a high heat of vaporization
(40.65 kJ·mol −1 ), both of which are a result of
the extensive hydrogen bonding between its molecules. These two
unusual properties allow water to moderate Earth's climate by
buffering large fluctuations in temperature.
The maximum density of water occurs at 3.98 °C
(39.16 °F). [ 13 ] Water becomes even less dense upon
freezing, expanding 9%. This results in an unusual phenomenon:
water's solid form, ice, floats upon water, allowing organisms to
survive inside a partially-frozen water body because the water on
the bottom has a temperature of around 4 °C
(39 °F).
ADR label for transporting goods dangerously reactive with
water
Water is miscible with many liquids, such as ethanol , in all
proportions, forming a single homogeneous liquid. On the other
hand, water and most oils are immiscible usually forming layers
according to increasing density from the top. As a gas, water vapor
is completely miscible with air.
Water forms an azeotrope with many other solvents.
Water can be split by electrolysis into hydrogen and oxygen.
As an oxide of hydrogen, water is formed when hydrogen or
hydrogen-containing compounds burn or react with oxygen or
oxygen-containing compounds. Water is not a fuel , it is an
end-product of the combustion of hydrogen. The energy required to
split water into hydrogen and oxygen by electrolysis or any other
means is greater than the energy released when the hydrogen and
oxygen recombine. [ 14 ]
Elements which are more electropositive than hydrogen such as
lithium , sodium , calcium , potassium and caesium displace
hydrogen from water, forming hydroxides . Being a flammable gas,
the hydrogen given off is dangerous and the reaction of water with
the more electropositive of these elements may be violently
explosive.
Taste and odor
Water can dissolve many different substances, giving it varying
tastes and odors. Humans and other animals have developed senses
which (more or less) enable them to evaluate the potability of
water by avoiding water that is too salty or putrid . Humans also
tend to prefer cold water to lukewarm water since cold water is
likely to contain fewer microbes . The taste advertised in spring
water or mineral water derives from the minerals dissolved in it:
Pure H 2 O is tasteless and odorless. The advertised purity of
spring and mineral water refers to absence of toxins , pollutants
and microbes .
Distribution of water in nature
Water in the universe
Much of the universe's water may be produced as a byproduct of star
formation . When stars are born, their birth is accompanied by a
strong outward wind of gas and dust. When this outflow of material
eventually impacts the surrounding gas, the shock waves that are
created compress and heat the gas. The water observed is quickly
produced in this warm dense gas. [ 15 ]
Water has been detected in interstellar clouds within our galaxy ,
the Milky Way . Water probably exists in abundance in other
galaxies, too, because its components, hydrogen and oxygen, are
among the most abundant elements in the universe. Interstellar
clouds eventually condense into solar nebulae and solar systems
such as ours.
Water vapor is present in:
Atmosphere of Mercury : 3.4%, and large amounts of water in
Mercury's exosphere [ 16 ]
Atmosphere of Venus : 0.002%
Earth's atmosphere : ~0.40% over full atmosphere, typically 1%-4%
at surface
Atmosphere of Mars : 0.03%
Atmosphere of Jupiter : 0.0004%
Atmosphere of Saturn - in ices only
Enceladus (moon of Saturn): 91%
exoplanets known as HD 189733 b [ 17 ] and HD 209458 b . [ 18 ]
Liquid water is present on:
Earth - 71% of surface
Moon - small amounts of water have been found (in 2008) in the
inside of volcanic pearls brought from Moon to Earth by the Apollo
15 crew in 1971. [ 19 ] NASA reported the detection of water
molecules by NASA's Moon Mineralogy Mapper aboard the Indian Space
Research Organization's Chandrayaan-1 spacecraft in September 2009.
[ 20 ]
Strong evidence suggests that liquid water is present just under
the surface of Saturn's moon Enceladus and on Jupiter's moon Europa
where it may exist as a 100 km deep ocean covering the whole
moon which would amount to more water than is in all the Earth's
oceans.
Water ice is present on:
Earth - mainly as ice sheets
polar ice caps on Mars
Moon
Titan
Europa
Saturn's rings [ 21 ]
Enceladus
Pluto and Charon [ 22 ]
Comets and comet source populations ( Kuiper belt and Oort cloud
objects).
Water ice may be present on Ceres and Tethys . Water and other
volatiles probably comprise much of the internal structures of
Uranus and Neptune .
Water and habitable zone
The Solar System along center row range of possible habitable zones
of varying size stars.
The existence of liquid water, and to a lesser extent its gaseous
and solid forms, on Earth are vital to the existence of life on
Earth as we know it. The Earth is located in the habitable zone of
the solar system ; if it were slightly closer to or further from
the Sun (about 5%, or about 8 million kilometers), the conditions
which allow the three forms to be present simultaneously would be
far less likely to exist. [ 23 ] [ 24 ]
Earth's gravity allows it to hold an atmosphere . Water vapor and
carbon dioxide in the atmosphere provide a temperature buffer (
greenhouse effect ) which helps maintain a relatively steady
surface temperature. If Earth were smaller, a thinner atmosphere
would allow temperature extremes, thus preventing the accumulation
of water except in polar ice caps (as on Mars ).
The surface temperature of Earth has been relatively constant
through geologic time despite varying levels of incoming solar
radiation ( insolation ), indicating that a dynamic process governs
Earth's temperature via a combination of greenhouse gases and
surface or atmospheric albedo . This proposal is known as the Gaia
hypothesis .
The state of water on a planet depends on ambient pressure, which
is determined by the planet's gravity. If a planet is sufficiently
massive, the water on it may be solid even at high temperatures,
because of the high pressure caused by gravity.
There are various theories about origin of water on Earth .
Water on Earth
Main articles: Hydrology and Water distribution on Earth
A graphical distribution of the locations of water on Earth.
Water covers 71% of the Earth's surface; the oceans contain 97.2%
of the Earth's water. The Antarctic ice sheet , which contains 90%
of all fresh water on Earth, is visible at the bottom. Condensed
atmospheric water can be seen as clouds , contributing to the
Earth's albedo .
Hydrology is the study of the movement, distribution, and quality
of water throughout the Earth. The study of the distribution of
water is hydrography . The study of the distribution and movement
of groundwater is hydrogeology , of glaciers is glaciology , of
inland waters is limnology and distribution of oceans is
oceanography . Ecological processes with hydrology are in focus of
ecohydrology .
The collective mass of water found on, under, and over the surface
of a planet is called the hydrosphere . Earth's approximate water
volume (the total water supply of the world) is
1,360,000,000 km 3 (326,000,000 mi 3 ).
Groundwater and fresh water are useful or potentially useful to
humans as water resources .
Liquid water is found in bodies of water , such as an ocean, sea ,
lake , river , stream , canal , pond , or puddle . The majority of
water on Earth is sea water . Water is also present in the
atmosphere in solid, liquid, and vapor states. It also exists as
groundwater in aquifers .
Water is important in many geological processes. Groundwater is
ubiquitous in rocks , and the pressure of this groundwater affects
patterns of faulting . Water in the mantle is responsible for the
melt that produces volcanoes at subduction zones . On the surface
of the Earth, water is important in both chemical and physical
weathering processes. Water and, to a lesser but still significant
extent, ice, are also responsible for a large amount of sediment
transport that occurs on the surface of the earth. Deposition of
transported sediment forms many types of sedimentary rocks , which
make up the geologic record of Earth history .
Water cycle
Main article: Water cycle
Water cycle
The water cycle (known scientifically as the hydrologic cycle )
refers to the continuous exchange of water within the hydrosphere ,
between the atmosphere , soil water, surface water , groundwater ,
and plants .
Water moves perpetually through each of these regions in the water
cycle consisting of following transfer processes:
evaporation from oceans and other water bodies into the air and
transpiration from land plants and animals into air.
precipitation , from water vapor condensing from the air and
falling to earth or ocean.
runoff from the land usually reaching the sea .
Most water vapor over the oceans returns to the oceans, but winds
carry water vapor over land at the same rate as runoff into the
sea, about 36 Tt per year. Over land, evaporation and
transpiration contribute another 71 Tt per year.
Precipitation, at a rate of 107 Tt per year over land, has several
forms: most commonly rain , snow , and hail , with some
contribution from fog and dew . Condensed water in the air may also
refract sunlight to produce rainbows .
Water runoff often collects over watersheds flowing into rivers. A
mathematical model used to simulate river or stream flow and
calculate water quality parameters is hydrological transport model
. Some of water is diverted to irrigation for agriculture. Rivers
and seas offer opportunity for travel and commerce . Through
erosion , runoff shapes the environment creating river valleys and
deltas which provide rich soil and level ground for the
establishment of population centers. A flood occurs when an area of
land, usually low-lying, is covered with water. It is when a river
overflows its banks or flood from the sea. A drought is an extended
period of months or years when a region notes a deficiency in its
water supply. This occurs when a region receives consistently below
average precipitation.
Fresh water storage
High tide (left) and low tide (right)
Main article: Water resources
Some runoff water is trapped for periods of time, for example in
lakes. At high altitude, during winter, and in the far north and
south, snow collects in ice caps, snow pack and glaciers. Water
also infiltrates the ground and goes into aquifers. This
groundwater later flows back to the surface in springs , or more
spectacularly in hot springs and geysers . Groundwater is also
extracted artificially in wells . This water storage is important,
since clean, fresh water is essential to human and other land-based
life. In many parts of the world, it is in short supply.
Sea water
Main article: Seawater
Sea water contains about 3.5% salt on average, plus smaller amounts
of other substances. The physical properties of sea water differ
from fresh water in some important respects. It freezes at a lower
temperature (about -1.9C) and its density increases with decreasing
temperature to the freezing point, instead of reaching maximum
density at a temperature above freezing. The salinity of water in
major seas varies from about 0.7% in the Baltic Sea to 4.0% in the
Red Sea .
Tides
Main article: Tide
Tides are the cyclic rising and falling of Earth's ocean surface
caused by the tidal forces of the Moon and the Sun acting on the
oceans. Tides cause changes in the depth of the marine and
estuarine water bodies and produce oscillating currents known as
tidal streams. The changing tide produced at a given location is
the result of the changing positions of the Moon and Sun relative
to the Earth coupled with the effects of Earth rotation and the
local bathymetry . The strip of seashore that is submerged at high
tide and exposed at low tide, the intertidal zone , is an important
ecological product of ocean tides.
Effects on life
An oasis is an isolated water source with vegetation in desert
Overview of photosynthesis and respiration . Water (at right),
together with carbon dioxide (CO 2 ), form oxygen and organic
compounds (at left), which can be respired to water and (CO 2
).
From a biological standpoint, water has many distinct properties
that are critical for the proliferation of life that set it apart
from other substances. It carries out this role by allowing organic
compounds to react in ways that ultimately allow replication . All
known forms of life depend on water. Water is vital both as a
solvent in which many of the body's solutes dissolve and as an
essential part of many metabolic processes within the body.
Metabolism is the sum total of anabolism and catabolism. In
anabolism, water is removed from molecules (through energy
requiring enzymatic chemical reactions) in order to grow larger
molecules (e.g. starches, triglycerides and proteins for storage of
fuels and information). In catabolism, water is used to break bonds
in order to generate smaller molecules (e.g. glucose, fatty acids
and amino acids to be used for fuels for energy use or other
purposes). Water is thus essential and central to these metabolic
processes. Therefore, without water, these metabolic processes
would cease to exist, leaving us to muse about what processes would
be in its place, such as gas absorption, dust collection, etc.
Water is also central to photosynthesis and respiration.
Photosynthetic cells use the sun's energy to split off water's
hydrogen from oxygen. Hydrogen is combined with CO 2 (absorbed from
air or water) to form glucose and release oxygen. All living cells
use such fuels and oxidize the hydrogen and carbon to capture the
sun's energy and reform water and CO 2 in the process (cellular
respiration).
Water is also central to acid-base neutrality and enzyme function.
An acid, a hydrogen ion (H + , that is, a proton) donor, can be
neutralized by a base, a proton acceptor such as hydroxide ion (OH
− ) to form water. Water is considered to be neutral, with a
pH (the negative log of the hydrogen ion concentration) of 7. Acids
have pH values less than 7 while bases have values greater than
7.
Some of the biodiversity of a coral reef
Stomach acid (HCl) is useful to digestion. However, its corrosive
effect on the esophagus during reflux can temporarily be
neutralized by ingestion of a base such as aluminum hydroxide to
produce the neutral molecules water and the salt aluminum chloride.
Human biochemistry that involves enzymes usually performs optimally
around a biologically neutral pH of 7.4.
For example, a cell of Escherichia coli contains 70% of water, a
human body 60–70%, plant body up to 90% and the body of an
adult jellyfish is made up of 94–98% water.
Aquatic life forms
Main articles: Hydrobiology and Aquatic plant
Some marine diatoms - a key phytoplankton group
Earth's waters are filled with life. The earliest life forms
appeared in water; nearly all fish live exclusively in water, and
there are many types of marine mammals, such as dolphins and whales
that also live in the water. Some kinds of animals, such as
amphibians , spend portions of their lives in water and portions on
land. Plants such as kelp and algae grow in the water and are the
basis for some underwater ecosystems. Plankton is generally the
foundation of the ocean food chain .
Aquatic animals must obtain oxygen to survive, and they do so in
various ways. Fish have gills instead of lungs , although some
species of fish, such as the lungfish , have both. Marine mammals ,
such as dolphins, whales, otters , and seals need to surface
periodically to breathe air. Smaller life forms are able to absorb
oxygen through their skin.
Effects on human civilization
Water fountain
Civilization has historically flourished around rivers and major
waterways; Mesopotamia , the so-called cradle of civilization, was
situated between the major rivers Tigris and Euphrates ; the
ancient society of the Egyptians depended entirely upon the Nile .
Large metropolises like Rotterdam , London , Montreal , Paris , New
York City , Buenos Aires , Shanghai , Tokyo , Chicago , and Hong
Kong owe their success in part to their easy accessibility via
water and the resultant expansion of trade. Islands with safe water
ports, like Singapore , have flourished for the same reason. In
places such as North Africa and the Middle East , where water is
more scarce, access to clean drinking water was and is a major
factor in human development.
Health and pollution
Environmental Science Program, Iowa State University student
sampling water.
Water fit for human consumption is called drinking water or potable
water . Water that is not potable can be made potable by filtration
or distillation (heating it until it becomes water vapor, and then
capturing the vapor without any of the impurities it leaves
behind), or by other methods (chemical or heat treatment that kills
bacteria). Sometimes the term safe water is applied to potable
water of a lower quality threshold (i.e., it is used effectively
for nutrition in humans that have weak access to water cleaning
processes, and does more good than harm). Water that is not fit for
drinking but is not harmful for humans when used for swimming or
bathing is called by various names other than potable or drinking
water, and is sometimes called safe water , or "safe for bathing".
Chlorine is a skin and mucous membrane irritant that is used to
make water safe for bathing or drinking. Its use is highly
technical and is usually monitored by government regulations
(typically 1 part per million (ppm) for drinking water, and
1–2 ppm of chlorine not yet reacted with impurities for
bathing water).
This natural resource is becoming scarcer in certain places, and
its availability is a major social and economic concern. Currently,
about a billion people around the world routinely drink unhealthy
water. Most countries accepted the goal of halving by 2015 the
number of people worldwide who do not have access to safe water and
sanitation during the 2003 G8 Evian summit . [ 25 ] Even if this
difficult goal is met, it will still leave more than an estimated
half a billion people without access to safe drinking water and
over a billion without access to adequate sanitation. Poor water
quality and bad sanitation are deadly; some five million deaths a
year are caused by polluted drinking water. The World Health
Organization estimates that safe water could prevent 1.4 million
child deaths from diarrhea each year. [ 26 ] Water, however, is not
a finite resource, but rather re-circulated as potable water in
precipitation in quantities many degrees of magnitude higher than
human consumption. Therefore, it is the relatively small quantity
of water in reserve in the earth (about 1% of our drinking water
supply , which is replenished in aquifers around every 1 to 10
years), that is a non-renewable resource, and it is, rather, the
distribution of potable and irrigation water which is scarce,
rather than the actual amount of it that exists on the earth.
Water-poor countries use importation of goods as the primary method
of importing water (to leave enough for local human consumption),
since the manufacturing process uses around 10 to 100 times
products' masses in water.
In the developing world, 90% of all wastewater still goes untreated
into local rivers and streams. [ 27 ] Some 50 countries, with
roughly a third of the world’s population, also suffer from
medium or high water stress, and 17 of these extract more water
annually than is recharged through their natural water cycles. [ 28
] The strain not only affects surface freshwater bodies like rivers
and lakes, but it also degrades groundwater resources.
Human uses
Agriculture
Irrigation of field crops
The most important use of water in agriculture is for irrigation ,
which is a key component to produce enough food. Irrigation takes
up to 90% of water withdrawn in some developing countries [ 29 ]
and significant proportions in more economically developed
countries (United States, 30% of freshwater usage is for
irrigation). [ 30 ]
Water as a scientific standard
On 7 April 1795, the gram was defined in France to be equal to "the
absolute weight of a volume of pure water equal to a cube of one
hundredth of a meter, and to the temperature of the melting ice." [
31 ] For practical purposes though, a metallic reference standard
was required, one thousand times more massive, the kilogram . Work
was therefore commissioned to determine precisely the mass of one
liter of water. In spite of the fact that the decreed definition of
the gram specified water at 0 °C—a highly
reproducible temperature —the scientists chose to redefine
the standard and to perform their measurements at the temperature
of highest water density , which was measured at the time as
4 °C (39 °F). [ 32 ]
The Kelvin temperature scale of the SI system is based on the
triple point of water, defined as exactly 273.16 K or
0.01 °C. The scale is a more accurate development of the
Celsius temperature scale, which was originally defined according
the boiling point (set to 100 °C) and melting point (set
to 0 °C) of water.
Natural water consists mainly of the isotopes hydrogen-1 and
oxygen-16, but there is also small quantity of heavier isotopes
such as hydrogen-2 ( deuterium ). The amount of deuterium oxides or
heavy water is very small, but it still affects the properties of
water. Water from rivers and lakes tends to contain less deuterium
than seawater. Therefore, standard water is defined in the Vienna
Standard Mean Ocean Water specification.
For drinking
Main article: Drinking water
A young girl drinking bottled water
Water quality: fraction of population using improved water sources
by country
The human body is anywhere from 55% to 78% water depending on body
size. [ 33 ] To function properly, the body requires between one
and seven liters of water per day to avoid dehydration ; the
precise amount depends on the level of activity, temperature,
humidity, and other factors. Most of this is ingested through foods
or beverages other than drinking straight water. It is not clear
how much water intake is needed by healthy people, though most
advocates agree that 6–7 glasses of water (approximately 2
liters) daily is the minimum to maintain proper hydration. [ 34 ]
Medical literature favors a lower consumption, typically 1 liter of
water for an average male, excluding extra requirements due to
fluid loss from exercise or warm weather. [ 35 ] For those who have
healthy kidneys, it is rather difficult to drink too much water,
but (especially in warm humid weather and while exercising) it is
dangerous to drink too little. People can drink far more water than
necessary while exercising, however, putting them at risk of water
intoxication (hyperhydration), which can be fatal. The "fact" that
a person should consume eight glasses of water per day cannot be
traced back to a scientific source. [ 36 ] There are other myths
such as the effect of water on weight loss and constipation that
have been dispelled. [ 37 ]
Hazard symbol for No drinking water
An original recommendation for water intake in 1945 by the Food and
Nutrition Board of the National Research Council read: "An ordinary
standard for diverse persons is 1 milliliter for each calorie of
food. Most of this quantity is contained in prepared foods." [ 38 ]
The latest dietary reference intake report by the United States
National Research Council in general recommended (including food
sources): 2.7 liters of water total for women and 3.7 liters for
men. [ 39 ] Specifically, pregnant and breastfeeding women need
additional fluids to stay hydrated. According to the Institute of
Medicine —who recommend that, on average, women consume 2.2
liters and men 3.0 liters—this is recommended to be 2.4
liters (10 cups) for pregnant women and 3 liters (12 cups) for
breastfeeding women since an especially large amount of fluid is
lost during nursing. [ 40 ] Also noted is that normally, about 20%
of water intake comes from food, while the rest comes from drinking
water and beverages ( caffeinated included). Water is excreted from
the body in multiple forms; through urine and faeces , through
sweating , and by exhalation of water vapor in the breath. With
physical exertion and heat exposure, water loss will increase and
daily fluid needs may increase as well.
Humans require water that does not contain too many impurities.
Common impurities include metal salts and oxides (including copper,
iron, calcium and lead) [ 41 ] and/or harmful bacteria , such as
Vibrio . Some solutes are acceptable and even desirable for taste
enhancement and to provide needed electrolytes . [ 42 ]
The single largest freshwater resource suitable for drinking is
Lake Baikal in Siberia, which has a very low salt and calcium
content and is therefore very clean.
Hygiene
The ability of water to make solutions and emulsions is used for
washing. Many industrial processes rely on reactions using
chemicals dissolved in water, suspension of solids in water
slurries or using water to dissolve and extract substances.
Chemical uses
Water is widely used in chemical reactions as a solvent or reactant
and less commonly as a solute or catalyst. In inorganic reactions,
water is a common solvent, dissolving many ionic compounds. In
organic reactions, it is not usually used as a reaction solvent,
because it does not dissolve the reactants well and is amphoteric
(acidic and basic) and nucleophilic . Nevertheless, these
properties are sometimes desirable. Also, acceleration of
Diels-Alder reactions by water has been observed. Supercritical
water has recently been a topic of research. Oxygen-saturated
supercritical water combusts organic pollutants efficiently.
As a heat transfer fluid
Ice used for cooling.
Water and steam are used as heat transfer fluids in diverse heat
exchange systems, due to its availability and high heat capacity,
both as a coolant and for heating. Cool water may even be naturally
available from a lake or the sea. Condensing steam is a
particularly efficient heating fluid because of the large heat of
vaporization. A disadvantage is that water and steam are somewhat
corrosive. In almost all electric power stations , water is the
coolant, which vaporizes and drives steam turbines to drive
generators. In the U.S., cooling power plants is the largest use of
water. [ 30 ]
In the nuclear industry, water can also be used as a neutron
moderator . In a pressurized water reactor , water is both a
coolant and a moderator. This provides a passive safety measure, as
removing the water from the reactor also slows the nuclear reaction
down.
Extinguishing fires
Water is used for fighting wildfires .
Water has a high heat of vaporization and is relatively inert,
which makes it a good fire extinguishing fluid. The evaporation of
water carries heat away from the fire. However, water cannot be
used to fight fires of electric equipment, because impure water is
electrically conductive, or of oils and organic solvents, because
they float on water and the explosive boiling of water tends to
spread the burning liquid.
Use of water in fire fighting should also take into account the
hazards of a steam explosion , which may occur when water is used
on very hot fires in confined spaces, and of a hydrogen explosion,
when substances which react with water, such as certain metals or
hot graphite, decompose the water, producing hydrogen gas .
The power of such explosions was seen in the Chernobyl disaster ,
although the water involved did not come from fire-fighting at that
time but the reactor's own water cooling system. A steam explosion
occurred when the extreme over-heating of the core caused water to
flash into steam. A hydrogen explosion may have occurred as a
result of reaction between steam and hot zirconium .
Recreation
Main article: Water sport (recreation)
Humans use water for many recreational purposes, as well as for
exercising and for sports. Some of these include swimming ,
waterskiing , boating , surfing and diving . In addition, some
sports, like ice hockey and ice skating , are played on ice.
Lakesides, beaches and waterparks are popular places for people to
go to relax and enjoy recreation. Many find the sound and
appearance of flowing water to be calming, and fountains and other
water features in public or private decorations.. Some keep fish
and other life in aquariums or ponds for show, fun, and
companionship. Humans also use water for snow sports i.e. skiing ,
sledding , snowmobiling or snowboarding , which requires the water
to be frozen. People may also use water for play fighting such as
with snowballs , water guns or water balloons .
Water industry
A water-carrier in India , 1882. In many places where running water
was not available, water had to be transported by people.
A manual water pump in China
Water purification facility
Main articles: Water industry and :Category:Water supply and
sanitation by country
The water industry provides drinking water and wastewater services
(including sewage treatment ) to households and industry . Water
supply facilities include water wells cisterns for rainwater
harvesting , water supply network , water purification facilities,
water tanks , water towers , water pipes including old aqueducts .
Atmospheric water generators are in development.
Drinking water is often collected at springs , extracted from
artificial borings (wells) in the ground, or pumped from lakes and
rivers. Building more wells in adequate places is thus a possible
way to produce more water, assuming the aquifers can supply an
adequate flow. Other water sources include rainwater collection.
Water may require purification for human consumption. This may
involve removal of undissolved substances, dissolved substances and
harmful microbes . Popular methods are filtering with sand which
only removes undissolved material, while chlorination and boiling
kill harmful microbes. Distillation does all three functions. More
advanced techniques exist, such as reverse osmosis . Desalination
of abundant seawater is a more expensive solution used in coastal
arid climates .
The distribution of drinking water is done through municipal water
systems , tanker delivery or as bottled water . Governments in many
countries have programs to distribute water to the needy at no
charge. Others argue that the market mechanism and free enterprise
are best to manage this rare resource and to finance the boring of
wells or the construction of dams and reservoirs .
Reducing usage by using drinking (potable) water only for human
consumption is another option. In some cities such as Hong Kong ,
sea water is extensively used for flushing toilets citywide in
order to conserve fresh water resources .
Polluting water may be the biggest single misuse of water; to the
extent that a pollutant limits other uses of the water, it becomes
a waste of the resource, regardless of benefits to the polluter.
Like other types of pollution, this does not enter standard
accounting of market costs, being conceived as externalities for
which the market cannot account. Thus other people pay the price of
water pollution, while the private firms' profits are not
redistributed to the local population victim of this pollution.
Pharmaceuticals consumed by humans often end up in the waterways
and can have detrimental effects on aquatic life if they
bioaccumulate and if they are not biodegradable .
Wastewater facilities are storm sewers and wastewater treatment
plants . Another way to remove pollution from surface runoff water
is bioswale .
Industrial applications
Water is used in power generation . Hydroelectricity is electricity
obtained from hydropower . Hydroelectric power comes from water
driving a water turbine connected to a generator. Hydroelectricity
is a low-cost, non-polluting, renewable energy source. The energy
is supplied by the sun. Heat from the sun evaporates water, which
condenses as rain in higher altitudes, from where it flows
down.
Three Gorges Dam is the largest hydro-electric power station .
Pressurized water is used in water blasting and water jet cutters .
Also, very high pressure water guns are used for precise cutting.
It works very well, is relatively safe, and is not harmful to the
environment. It is also used in the cooling of machinery to prevent
over-heating, or prevent saw blades from over-heating.
Water is also used in many industrial processes and machines, such
as the steam turbine and heat exchanger , in addition to its use as
a chemical solvent . Discharge of untreated water from industrial
uses is pollution . Pollution includes discharged solutes (
chemical pollution ) and discharged coolant water (thermal
pollution). Industry requires pure water for many applications and
utilizes a variety of purification techniques both in water supply
and discharge.
Food processing
Water can be used to cook foods such as noodles .
Water plays many critical roles within the field of food science .
It is important for a food scientist to understand the roles that
water plays within food processing to ensure the success of their
products.
Solutes such as salts and sugars found in water affect the physical
properties of water. The boiling and freezing points of water is
affected by solutes. One mole of sucrose (sugar) per kilogram of
water raises the boiling point of water by 0.51 °C, and one
mole of salt per kg raises the boiling point by 1.02 °C;
similarly, increasing the number of dissolved particles lowers
water's freezing point. [ 43 ] Solutes in water also affect water
activity which affects many chemical reactions and the growth of
microbes in food. [ 44 ] Water activity can be described as a ratio
of the vapor pressure of water in a solution to the vapor pressure
of pure water. [ 43 ] Solutes in water lower water activity. This
is important to know because most bacterial growth ceases at low
levels of water activity. [ 44 ] Not only does microbial growth
affect the safety of food but also the preservation and shelf life
of food.
Water hardness is also a critical factor in food processing. It can
dramatically affect the quality of a product as well as playing a
role in sanitation. Water hardness is classified based on the
amounts of removable calcium carbonate salt it contains per gallon.
Water hardness is measured in grains; 0.064 g calcium carbonate is
equivalent to one grain of hardness. [ 43 ] Water is classified as
soft if it contains 1 to 4 grains, medium if it contains 5 to 10
grains and hard if it contains 11 to 20 grains. [ vague ] [ 43 ]
The hardness of water may be altered or treated by using a chemical
ion exchange system. The hardness of water also affects its pH
balance which plays a critical role in food processing. For
example, hard water prevents successful production of clear
beverages. Water hardness also affects sanitation; with increasing
hardness, there is a loss of effectiveness for its use as a
sanitizer. [ 43 ]
Boiling , steaming , and simmering are popular cooking methods that
often require immersing food in water or its gaseous state, steam.
Water is also used for dishwashing .
Water law, water politics and water crisis
Best estimate of the share of people in developing countries with
access to drinking water 1970–2000
Main articles: Water law , Water right , Water politics , and Water
crisis
See also: Water resources
Water politics is politics affected by water and water resources .
For this reason, water is a strategic resource in the globe and an
important element in many political conflicts. It causes health
impacts and damage to biodiversity.
1.6 billion people have gained access to a safe water source since
1990 [1] . The proportion of people in developing countries with
access to safe water is calculated to have improved from 30% in
1970 [ 4 ] to 71% in 1990, 79% in 2000 and 84% in 2004. This trend
is projected to continue. [ 5 ] To halve, by 2015, the proportion
of people without sustainable access to safe drinking water is one
of the Millennium Development Goals . This goal is projected to be
reached.
A 2006 United Nations report stated that "there is enough water for
everyone", but that access to it is hampered by mismanagement and
corruption. [ 45 ]
The UN World Water Development Report (WWDR, 2003) from the World
Water Assessment Program indicates that, in the next 20 years, the
quantity of water available to everyone is predicted to decrease by
30%. 40% of the world's inhabitants currently have insufficient
fresh water for minimal hygiene . More than 2.2 million people died
in 2000 from waterborne diseases (related to the consumption of
contaminated water) or drought . In 2004, the UK charity WaterAid
reported that a child dies every 15 seconds from easily preventable
water-related diseases; often this means lack of sewage disposal;
see toilet .
Organizations concerned with water protection include International
Water Association (IWA), WaterAid , Water 1st , American Water
Resources Association . Water related conventions are United
Nations Convention to Combat Desertification (UNCCD), International
Convention for the Prevention of Pollution from Ships , United
Nations Convention on the Law of the Sea and Ramsar Convention .
World Day for Water takes place on 22 March and World Ocean Day on
8 June.
Water used in the production of a good or service is virtual water
.
Water in culture
Religion
Main article: Water and religion
Water is considered a purifier in most religions. Major faiths that
incorporate ritual washing ( ablution ) include Christianity ,
Hinduism , Rastafari movement , Islam , Shinto , Taoism , and
Judaism . Immersion (or aspersion or affusion ) of a person in
water is a central sacrament of Christianity (where it is called
baptism ); it is also a part of the practice of other religions,
including Judaism ( mikvah ) and Sikhism ( Amrit Sanskar ). In
addition, a ritual bath in pure water is performed for the dead in
many religions including Judaism and Islam. In Islam, the five
daily prayers can be done in most cases (see Tayammum ) after
completing washing certain parts of the body using clean water (
wudu ). In Shinto, water is used in almost all rituals to cleanse a
person or an area (e.g., in the ritual of misogi ). Water is
mentioned in the Bible 442 times in the New International Version
and 363 times in the King James Version : 2 Peter 3:5(b) states,
"The earth was formed out of water and by water" (NIV). In the
Koran it is stated that "Living things are made of water" and it is
often used to described Paradise.
Philosophy
The Ancient Greek philosopher Empedocles held that water is one of
the four classical elements along with fire , earth and air , and
was regarded as the ylem , or basic substance of the universe.
Water was considered cold and moist. In the theory of the four
bodily humors , water was associated with phlegm . The classical
element of Water was also one of the five elements in traditional
Chinese philosophy , along with earth , fire , wood , and metal
.
Water is also taken as a role model in some parts of traditional
and popular Asian philosophy. James Legge's 1891 translation of the
Dao De Jing states "The highest excellence is like (that of) water.
The excellence of water appears in its benefiting all things, and
in its occupying, without striving (to the contrary), the low place
which all men dislike. Hence (its way) is near to (that of) the
Tao" and "There is nothing in the world more soft and weak than
water, and yet for attacking things that are firm and strong there
is nothing that can take precedence of it—for there is
nothing (so effectual) for which it can be changed." [ 46 ]
Literature
Water is used in literature as a symbol of purification. Examples
include the critical importance of a river in As I Lay Dying by
William Faulkner and the drowning of Ophelia in Hamlet .
Sherlock Holmes held that "From a drop of water, a logician could
infer the possibility of an Atlantic or a Niagara without having
seen or heard of one or the other." [ 47 ]
In chemistry , an alkali (from Arabic : Al-Qaly
القلي,
القالي ) is a basic , ionic
salt of an alkali metal or alkaline earth metal element . Alkalis
are best known for being bases that dissolve in water . Bases are
compounds with a pH greater than 7. The adjective alkaline is
commonly used in English as a synonym for base, especially for
soluble bases. This broad use of the term is likely to have come
about because alkalis were the first bases known to obey the
Arrhenius definition of a base and are still among the more common
bases. Since Brønsted-Lowry acid-base theory , the term
alkali in chemistry is normally restricted to those salts
containing alkali and alkaline earth metal elements.
Contents
1 Etymology
2 Common properties
3 Confusion between alkali and base
4 Salts
5 Alkaline soil
6 Lakes
7 References
//
Etymology
The word "alkali" is derived from Arabic al qalīy = the
calcined ashes , referring to the original source of alkaline
substance. Ashes were used in conjunction with animal fat to
produce soap , a process known as saponification .
Common properties
Alkalis are all Arrhenius bases, which form hydroxide ions (OH - )
when dissolved in water. Common properties of alkaline aqueous
solutions include:
Moderately-concentrated solutions (over 10 −3 M) have a pH of
7.1 or greater. This means that they will turn phenolphthalein from
colorless to pink.
Concentrated solutions are caustic (causing chemical burns).
Alkaline solutions are slippery or soapy to the touch, due to the
saponification of the fatty acids on the surface of the skin.
Alkalis are normally water soluble , although some like barium
carbonate are only soluble when reacting with an acidic aqueous
solution.
Acids and alkalis are measured on a pH scale
Alkalis are commonly found in household cleaners and toothpaste
Confusion between alkali and base
The terms "base" and "alkali" are often used interchangeably,
particularly outside of a scientific context, but they do not have
the same meaning. While all alkaline solutions are basic, not all
bases are alkaline. The following are common mistakes:
The phrase "measuring the alkalinity of soil" is incorrect since
the property measured is actually the pH (base property).
Calling bases that are not alkalis, such as ammonia , alkaline
(ammonia is a base but not an alkali).
Also, not all salts formed by alkali metals are alkaline; this
designation applies only to those salts that are basic. And while
most electropositive metal oxides are basic, only the soluble
alkali metal and alkaline earth metal oxides can be correctly
called alkalis.
This definition of an alkali as a basic salt of an alkali metal or
alkaline earth metal is the most common, based on dictionary
definitions [1] [2] , however conflicting definitions of the term
alkali do exist. These include:
Any base that is water-soluble and forms hydroxide ions [3] [4] .
In chemistry, this is more accurately called an Arrhenius base
.
The solution of a base in water [5] . This would be an Arrhenius
base in solution.
Name given by chemists to an important group of subtances, the
behaviour of bases the main alkali are 1,the hydroxides potassium
2,
Salts
Most basic salts are alkali salts, of which common examples
are:
sodium hydroxide (often called "caustic soda")
potassium hydroxide (commonly called "caustic potash")
lye (generic term, for either of the previous two, or even for a
mixture)
calcium carbonate (sometimes called "free lime")
magnesium hydroxide is an example of an atypical alkali since it
has low solubility in water (although the dissolved portion is
considered a strong base due to complete dissociation of its
ions).
Alkaline soil
Soil with a pH value higher than 7.3 is normally referred to as
alkaline. This soil property can occur naturally, due to the
presence of alkali salts. Although some plants do prefer slightly
basic soil (including vegetables like cabbage and fodder like
buffalograss ), most plants prefer a mildly acidic soil (pH between
6.0 and 6.8), and alkaline soils can cause problems.
Lakes
In alkali lakes (a type of salt lake ), evaporation concentrates
the naturally-occurring alkali salts, often forming a crust of
mildly-basic salt across a large area.
Examples of alkali lakes:
Redberry Lake, Saskatchewan , Canada .
Tramping Lake, Saskatchewan , Canada.
Mono lake , California , United States
Summer Lake , Oregon , United States
Alkali Lake, British Columbia and the adjoining reserves of the
Alkali Lake Indian Band are named for a local Alkali Lake, which
got its name from a large patch of alkali on the hillside above the
lake, which is not itself alkali, [ 1 ] although there are many in
the Cariboo district and adjoining regions of the British Columbia
Interior .
In chemistry , an alkali (from Arabic : Al-Qaly
القلي,
القالي ) is a basic , ionic
salt of an alkali metal or alkaline earth metal element . Alkalis
are best known for being bases that dissolve in water . Bases are
compounds with a pH greater than 7. The adjective alkaline is
commonly used in English as a synonym for base, especially for
soluble bases. This broad use of the term is likely to have come
about because alkalis were the first bases known to obey the
Arrhenius definition of a base and are still among the more common
bases. Since Brønsted-Lowry acid-base theory , the term
alkali in chemistry is normally restricted to those salts
containing alkali and alkaline earth metal elements.
Contents
1 Etymology
2 Common properties
3 Confusion between alkali and base
4 Salts
5 Alkaline soil
6 Lakes
7 References
//
Etymology
The word "alkali" is derived from Arabic al qalīy = the
calcined ashes , referring to the original source of alkaline
substance. Ashes were used in conjunction with animal fat to
produce soap , a process known as saponification .
Common properties
Alkalis are all Arrhenius bases, which form hydroxide ions (OH - )
when dissolved in water. Common properties of alkaline aqueous
solutions include:
Moderately-concentrated solutions (over 10 −3 M) have a pH of
7.1 or greater. This means that they will turn phenolphthalein from
colorless to pink.
Concentrated solutions are caustic (causing chemical burns).
Alkaline solutions are slippery or soapy to the touch, due to the
saponification of the fatty acids on the surface of the skin.
Alkalis are normally water soluble , although some like barium
carbonate are only soluble when reacting with an acidic aqueous
solution.
Acids and alkalis are measured on a pH scale
Alkalis are commonly found in household cleaners and toothpaste
Confusion between alkali and base
The terms "base" and "alkali" are often used interchangeably,
particularly outside of a scientific context, but they do not have
the same meaning. While all alkaline solutions are basic, not all
bases are alkaline. The following are common mistakes:
The phrase "measuring the alkalinity of soil" is incorrect since
the property measured is actually the pH (base property).
Calling bases that are not alkalis, such as ammonia , alkaline
(ammonia is a base but not an alkali).
Also, not all salts formed by alkali metals are alkaline; this
designation applies only to those salts that are basic. And while
most electropositive metal oxides are basic, only the soluble
alkali metal and alkaline earth metal oxides can be correctly
called alkalis.
This definition of an alkali as a basic salt of an alkali metal or
alkaline earth metal is the most common, based on dictionary
definitions [1] [2] , however conflicting definitions of the term
alkali do exist. These include:
Any base that is water-soluble and forms hydroxide ions [3] [4] .
In chemistry, this is more accurately called an Arrhenius base
.
The solution of a base in water [5] . This would be an Arrhenius
base in solution.
Name given by chemists to an important group of subtances, the
behaviour of bases the main alkali are 1,the hydroxides potassium
2,
Salts
Most basic salts are alkali salts, of which common examples
are:
sodium hydroxide (often called "caustic soda")
potassium hydroxide (commonly called "caustic potash")
lye (generic term, for either of the previous two, or even for a
mixture)
calcium carbonate (sometimes called "free lime")
magnesium hydroxide is an example of an atypical alkali since it
has low solubility in water (although the dissolved portion is
considered a strong base due to complete dissociation of its
ions).
Alkaline soil
Soil with a pH value higher than 7.3 is normally referred to as
alkaline. This soil property can occur naturally, due to the
presence of alkali salts. Although some plants do prefer slightly
basic soil (including vegetables like cabbage and fodder like
buffalograss ), most plants prefer a mildly acidic soil (pH between
6.0 and 6.8), and alkaline soils can cause problems.
Lakes
In alkali lakes (a type of salt lake ), evaporation concentrates
the naturally-occurring alkali salts, often forming a crust of
mildly-basic salt across a large area.
Examples of alkali lakes:
Redberry Lake, Saskatchewan , Canada .
Tramping Lake, Saskatchewan , Canada.
Mono lake , California , United States
Summer Lake , Oregon , United States
Alkali Lake, British Columbia and the adjoining reserves of the
Alkali Lake Indian Band are named for a local Alkali Lake, which
got its name from a large patch of alkali on the hillside above the
lake, which is not itself alkali, [ 1 ] although there are many in
the Cariboo district and adjoining regions of the British Columbia
Interior .
An antioxidant is a molecule capable of slowing or preventing the
oxidation of other molecules. Oxidation is a chemical reaction that
transfers electrons from a substance to an oxidizing agent .
Oxidation reactions can produce free radicals , which start chain
reactions that damage cells . Antioxidants terminate these chain
reactions by removing free radical intermediates, and inhibit other
oxidation reactions by being oxidized themselves. As a result,
antioxidants are often reducing agents such as thiols , ascorbic
acid or polyphenols . [ 1 ]
Although oxidation reactions are crucial for life, they can also be
damaging; hence, plants and animals maintain complex systems of
multiple types of antioxidants, such as glutathione , vitamin C ,
and vitamin E as well as enzymes such as catalase , superoxide
dismutase and various peroxidases . Low levels of antioxidants, or
inhibition of the antioxidant enzymes, cause oxidative stress and
may damage or kill cells.
As oxidative stress might be an important part of many human
diseases, the use of antioxidants in pharmacology is intensively
studied, particularly as treatments for stroke and
neurodegenerative diseases . However, it is unknown whether
oxidative stress is the cause or the consequence of disease.
Antioxidants are widely used as ingredients in dietary supplements
in the hope of maintaining health and preventing diseases such as
cancer and coronary heart disease . Although initial studies
suggested that antioxidant supplements might promote health, later
large clinical trials did not detect any benefit and suggested
instead that excess supplementation may be harmful. [ 2 ] In
addition to these uses of natural antioxidants in medicine, these
compounds have many industrial uses, such as preservatives in food
and cosmetics and preventing the degradation of rubber and gasoline
.
Contents
1 History
2 The oxidative challenge in biology
3 Metabolites
8 Measurement and levels in food
9 Uses in technology
9.1 Food preservatives
9.2 Industrial uses
10 See also
11 Further reading
12 References
13 External links
//
History
The term antioxidant originally was used to refer specifically to a
chemical that prevented the consumption of oxygen. In the late 19th
and early 20th century, extensive study was devoted to the uses of
antioxidants in important industrial processes, such as the
prevention of metal corrosion , the vulcanization of rubber, and
the polymerization of fuels in the fouling of internal combustion
engines . [ 3 ]
Early research on the role of antioxidants in biology focused on
their use in preventing the oxidation of unsaturated fats , which
is the cause of rancidity . [ 4 ] Antioxidant activity could be
measured simply by placing the fat in a closed container with
oxygen and measuring the rate of oxygen consumption. However, it
was the identification of vitamins A , C , and E as antioxidants
that revolutionized the field and led to the realization of the
importance of antioxidants in the biochemistry of living organisms
. [ 5 ] [ 6 ]
The possible mechanisms of action of antioxidants were first
explored when it was recognized that a substance with
anti-oxidative activity is likely to be one that is itself readily
oxidized. [ 7 ] Research into how vitamin E prevents the process of
lipid peroxidation led to the identification of antioxidants as
reducing agents that prevent oxidative reactions, often by
scavenging reactive oxygen species before they can damage cells. [
8 ]
The oxidative challenge in biology
Further information: Oxidative stress
The structure of the antioxidant vitamin ascorbic acid (vitamin
C).
A paradox in metabolism is that while the vast majority of complex
life on Earth requires oxygen for its existence, oxygen is a highly
reactive molecule that damages living organisms by producing
reactive oxygen species . [ 9 ] Consequently, organisms contain a
complex network of antioxidant metabolites and enzymes that work
together to prevent oxidative damage to cellular components such as
DNA , proteins and lipids . [ 1 ] [ 10 ] In general, antioxidant
systems either prevent these reactive species from being formed, or
remove them before they can damage vital components of the cell. [
1 ] [ 9 ] However, since reactive oxygen species do have useful
functions in cells, such as redox signaling , the function of
antioxidant systems is not to remove oxidants entirely, but instead
to keep them at an optimum level. [ 11 ]
The reactive oxygen species produced in cells include hydrogen
peroxide (H 2 O 2 ), hypochlorous acid (HOCl), and free radicals
such as the hydroxyl radical (·OH) and the superoxide anion
(O 2 − ). [ 12 ] The hydroxyl radical is particularly
unstable and will react rapidly and non-specifically with most
biological molecules. This species is produced from hydrogen
peroxide in metal-catalyzed redox reactions such as the Fenton
reaction . [ 13 ] These oxidants can damage cells by starting
chemical chain reactions such as lipid peroxidation, or by
oxidizing DNA or proteins. [ 1 ] Damage to DNA can cause mutations
and possibly cancer , if not reversed by DNA repair mechanisms, [
14 ] [ 15 ] while damage to proteins causes enzyme inhibition,
denaturation and protein degradation . [ 16 ]
The use of oxygen as part of the process for generating metabolic
energy produces reactive oxygen species. [ 17 ] In this process,
the superoxide anion is produced as a by-product of several steps
in the electron transport chain . [ 18 ] Particularly important is
the reduction of coenzyme Q in complex III , since a highly
reactive free radical is formed as an intermediate (Q ·
− ). This unstable intermediate can lead to electron
"leakage", when electrons jump directly to oxygen and form the
superoxide anion, instead of moving through the normal series of
well-controlled reactions of the electron transport chain. [ 19 ]
Peroxide is also produced from the oxidation of reduced
flavoproteins , such as complex I . [ 20 ] However, although these
enzymes can produce oxidants, the relative importance of the
electron transfer chain to other processes that generate peroxide
is unclear. [ 21 ] [ 22 ] In plants , algae , and cyanobacteria ,
reactive oxygen species are also produced during photosynthesis , [
23 ] particularly under conditions of high light intensity . [ 24 ]
This effect is partly offset by the involvement of carotenoids in
photoinhibition , which involves these antioxidants reacting with
over-reduced forms of the photosynthetic reaction centres to
prevent the production of reactive oxygen species. [ 25 ] [ 26
]
Metabolites
Overview
Antioxidants are classified into two broad divisions, depending on
whether they are soluble in water ( hydrophilic ) or in lipids (
hydrophobic ). In general, water-soluble antioxidants react with
oxidants in the cell cytosol and the blood plasma , while
lipid-soluble antioxidants protect cell membranes from lipid
peroxidation. [ 1 ] These compounds may be synthesized in the body
or obtained from the diet. [ 10 ] The different antioxidants are
present at a wide range of concentrations in body fluids and
tissues, with some such as glutathione or ubiquinone mostly present
within cells, while others such as uric acid are more evenly
distributed (see table below). Some antioxidants are only found in
a few organisms and these compounds can be important in pathogens
and can be virulence factors . [ 27 ]
The relative importance and interactions between these different
antioxidants is a very complex question, with the various
metabolites and enzyme systems having synergistic and
interdependent effects on one another. [ 28 ] [ 29 ] The action of
one antioxidant may therefore depend on the proper function of
other members of the antioxidant system. [ 10 ] The amount of
protection provided by any one antioxidant will also depend on its
concentration, its reactivity towards the particular reactive
oxygen species being considered, and the status of the antioxidants
with which it interacts. [ 10 ]
Some compounds contribute to antioxidant defense by chelating
transition metals and preventing them from catalyzing the
production of free radicals in the cell. Particularly important is
the ability to sequester iron , which is the function of
iron-binding proteins such as transferrin and ferritin . [ 30 ]
Selenium and zinc are commonly referred to as antioxidant nutrients
, but these chemical elements have no antioxidant action themselves
and are instead required for the activity of some antioxidant
enzymes, as is discussed below.
Antioxidant metabolite
Solubility
Concentration in human serum (μM) [ 31 ]
Concentration in liver tissue (μmol/kg)
Ascorbic acid ( vitamin C )
Water
50 – 60 [ 32 ]
260 (human) [ 33 ]
Ascorbic acid
Ascorbic acid or " vitamin C " is a monosaccharide antioxidant
found in both animals and plants. As one of the enzymes needed to
make ascorbic acid has been lost by mutation during human evolution
, it must be obtained from the diet and is a vitamin. [ 43 ] Most
other animals are able to produce this compound in their bodies and
do not require it in their diets. [ 44 ] In cells, it is maintained
in its reduced form by reaction with glutathione, which can be
catalysed by protein disulfide isomerase and glutaredoxins . [ 45 ]
[ 46 ] Ascorbic acid is a reducing agent and can reduce, and
thereby neutralize, reactive oxygen species such as hydrogen
peroxide. [ 47 ] In addition to its direct antioxidant effects,
ascorbic acid is also a substrate for the antioxidant enzyme
ascorbate peroxidase , a function that is particularly important in
stress resistance in plants. [ 48 ] Ascorbic acid is present at
high levels in all parts of plants and can reach concentrations of
20 millimolar in chloroplasts . [ 49 ]
Glutathione
The free radical mechanism of lipid peroxidation.
Glutathione is a cysteine -containing peptide found in most forms
of aerobic life. [ 50 ] It is not required in the diet and is
instead synthesized in cells from its constituent amino acids . [
51 ] Glutathione has antioxidant properties since the thiol group
in its cysteine moiety is a reducing agent and can be reversibly
oxidized and reduced. In cells, glutathione is maintained in the
reduced form by the enzyme glutathione reductase and in turn
reduces other metabolites and enzyme systems, such as ascorbate in
the glutathione-ascorbate cycle , glutathione peroxidases and
glutaredoxins , as well as reacting directly with oxidants. [ 45 ]
Due to its high concentration and its central role in maintaining
the cell's redox state, glutathione is one of the most important
cellular antioxidants. [ 50 ] In some organisms glutathione is
replaced by other thiols, such as by mycothiol in the Actinomycetes
, or by trypanothione in the Kinetoplastids . [ 52 ] [ 53 ]
Melatonin
Melatonin is a powerful antioxidant that can easily cross cell
membranes and the blood-brain barrier . [ 54 ] Unlike other
antioxidants, melatonin does not undergo redox cycling , which is
the ability of a molecule to undergo repeated reduction and
oxidation . Redox cycling may allow other antioxidants (such as
vitamin C) to act as pro-oxidants and promote free radical
formation. Melatonin, once oxidized, cannot be reduced to its
former state because it forms several stable end-products upon
reacting with free radicals. Therefore, it has been referred to as
a terminal (or suicidal) antioxidant. [ 55 ]
Tocopherols and tocotrienols (vitamin E)
Vitamin E is the collective name for a set of eight related
tocopherols and tocotrienols , which are fat-soluble vitamins with
antioxidant properties. [ 56 ] [ 57 ] Of these, α-tocopherol
has been most studied as it has the highest bioavailability , with
the body preferentially absorbing and metabolising this form. [ 58
]
It has been claimed that the α-tocopherol form is the most
important lipid-soluble antioxidant, and that it protects membranes
from oxidation by reacting with lipid radicals produced in the
lipid peroxidation chain reaction. [ 56 ] [ 59 ] This removes the
free radical intermediates and prevents the propagation reaction
from continuing. This reaction produces oxidised
α-tocopheroxyl radicals that can be recycled back to the
active reduced form through reduction by other antioxidants, such
as ascorbate, retinol or ubiquinol. [ 60 ] This is in line with
findings showing that α-tocopherol, but not water-soluble
antioxidants, efficiently protects glutathione peroxidase 4 ( GPX4
)-deficient cells from cell death [ 61 ] . GPx4 is the only known
enzyme that efficiently reduces lipid-hydroperoxides within
biological membranes.
However, the roles and importance of the various forms of vitamin E
are presently unclear, [ 62 ] [ 63 ] and it has even been suggested
that the most important function of α-tocopherol is as a
signaling molecule , with this molecule having no significant role
in antioxidant metabolism. [ 64 ] [ 65 ] The functions of the other
forms of vitamin E are even less well-understood, although
γ-tocopherol is a nucleophile that may react with
electrophilic mutagens, [ 58 ] and tocotrienols may be important in
protecting neurons from damage. [ 66 ]
Pro-oxidant activities
Further information: Pro-oxidant
Antioxidants that are reducing agents can also act as pro-oxidants.
For example, vitamin C has antioxidant activity when it reduces
oxidizing substances such as hydrogen peroxide, [ 67 ] however, it
will also reduce metal ions that generate free radicals through the
Fenton reaction . [ 68 ] [ 69 ]
2 Fe 3+ + Ascorbate → 2 Fe 2+ + Dehydroascorbate
2 Fe 2+ + 2 H 2 O 2 → 2 Fe 3+ + 2 OH · + 2 OH
−
The relative importance of the antioxidant and pro-oxidant
activities of antioxidants are an area of current research, but
vitamin C, for example, appears to have a mostly antioxidant action
in the body. [ 68 ] [ 70 ] However, less data is available for
other dietary antioxidants, such as vitamin E, [ 71 ] or the
polyphenols . [ 72 ]
Enzyme systems
Enzymatic pathway for detoxification of reactive oxygen
species.
Overview
As with the chemical antioxidants, cells are protected against
oxidative stress by an interacting network of antioxidant enzymes.
[ 1 ] [ 9 ] Here, the superoxide released by processes such as
oxidative phosphorylation is first converted to hydrogen peroxide
and then further reduced to give water. This detoxification pathway
is the result of multiple enzymes, with superoxide dismutases
catalysing the first step and then catalases and various
peroxidases removing hydrogen peroxide. As with antioxidant
metabolites, the contributions of these enzymes to antioxidant
defenses can be hard to separate from one another, but the
generation of transgenic mice lacking just one antioxidant enzyme
can be informative. [ 73 ]
Superoxide dismutase, catalase and peroxiredoxins
Superoxide dismutases (SODs) are a class of closely related enzymes
that catalyze the breakdown of the superoxide anion into oxygen and
hydrogen peroxide. [ 74 ] [ 75 ] SOD enzymes are present in almost
all aerobic cells and in extracellular fluids. [ 76 ] Superoxide
dismutase enzymes contain metal ion cofactors that, depending on
the isozyme, can be copper , zinc, manganese or iron . In humans,
the copper/zinc SOD is present in the cytosol , while manganese SOD
is present in the mitochondrion . [ 75 ] There also exists a third
form of SOD in extracellular fluids , which contains copper and
zinc in its active sites. [ 77 ] The mitochondrial isozyme seems to
be the most biologically important of these three, since mice
lacking this enzyme die soon after birth. [ 78 ] In contrast, the
mice lacking copper/zinc SOD (Sod1) are viable but have numerous
pathologies and a reduced lifespan (see article on superoxide ),
while mice without the extracellular SOD have minimal defects
(sensitive to hyperoxia ). [ 73 ] [ 79 ] In plants, SOD isozymes
are present in the cytosol and mitochondria, with an iron SOD found
in chloroplasts that is absent from vertebrates and yeast . [ 80
]
Catalases are enzymes that catalyse the conversion of hydrogen
peroxide to water and oxygen, using either an iron or manganese
cofactor. [ 81 ] [ 82 ] This protein is localized to peroxisomes in
most eukaryotic cells. [ 83 ] Catalase is an unusual enzyme since,
although hydrogen peroxide is its only substrate, it follows a
ping-pong mechanism . Here, its cofactor is oxidised by one
molecule of hydrogen peroxide and then regenerated by transferring
the bound oxygen to a second molecule of substrate. [ 84 ] Despite
its apparent importance in hydrogen peroxide removal, humans with
genetic deficiency of catalase — " acatalasemia " — or
mice genetically engineered to lack catalase completely, suffer few
ill effects. [ 85 ] [ 86 ]
Decameric structure of AhpC, a bacterial 2-cysteine peroxiredoxin
from Salmonella typhimurium . [ 87 ]
Peroxiredoxins are peroxidases that catalyze the reduction of
hydrogen peroxide, organic hydroperoxides , as well as
peroxynitrite . [ 88 ] They are divided into three classes: typical
2-cysteine peroxiredoxins; atypical 2-cysteine peroxiredoxins; and
1-cysteine peroxiredoxins. [ 89 ] These enzymes share the same
basic catalytic mechanism, in which a redox-active cysteine (the
peroxidatic cysteine) in the active site is oxidized to a sulfenic
acid by the peroxide substrate. [ 90 ] Over-oxidation of this
cysteine residue in peroxiredoxins inactivates these enzymes, but
this can be reversed by the action of sulfiredoxin . [ 91 ]
Peroxiredoxins seem to be important in antioxidant metabolism, as
mice lacking peroxiredoxin 1 or 2 have shortened lifespan and
suffer from hemolytic anaemia , while plants use peroxiredoxins to
remove hydrogen peroxide generated in chloroplasts. [ 92 ] [ 93 ] [
94 ]
Thioredoxin and glutathione systems
The thioredoxin system contains the 12-k Da protein thioredoxin and
its companion thioredoxin reductase . [ 95 ] Proteins related to
thioredoxin are present in all sequenced organisms with plants,
such as Arabidopsis thaliana , having a particularly great
diversity of isoforms. [ 96 ] The active site of thioredoxin
consists of two neighboring cysteines, as part of a highly
conserved CXXC motif , that can cycle between an active dithiol
form (reduced) and an oxidized disulfide form. In its active state,
thioredoxin acts as an efficient reducing agent, scavenging
reactive oxygen species and maintaining other proteins in their
reduced state. [ 97 ] After being oxidized, the active thioredoxin
is regenerated by the action of thioredoxin reductase, using NADPH
as an electron donor . [ 98 ]
The glutathione system includes glutathione, glutathione reductase
, glutathione peroxidases and glutathione S -transferases . [ 50 ]
This system is found in animals, plants and microorganisms. [ 50 ]
[ 99 ] Glutathione peroxidase is an enzyme containing four selenium
- cofactors that catalyzes the breakdown of hydrogen peroxide and
organic hydroperoxides. There are at least four different
glutathione peroxidase isozymes in animals. [ 100 ] Glutathione
peroxidase 1 is the most abundant and is a very efficient scavenger
of hydrogen peroxide, while glutathione peroxidase 4 is most active
with lipid hydroperoxides. Surprisingly, glutathione peroxidase 1
is dispensable, as mice lacking this enzyme have normal lifespans,
[ 101 ] but they are hypersensitive to induced oxidative stress. [
102 ] In addition, the glutathione S -transferases show high
activity with lipid peroxides. [ 103 ] These enzymes are at
particularly high levels in the liver and also serve in
detoxification metabolism. [ 104 ]
Oxidative stress in disease
Further information: Pathology , Free-radical theory of aging
Oxidative stress is thought to contribute to the development of a
wide range of diseases including Alzheimer's disease , [ 105 ] [
106 ] Parkinson's disease , [ 107 ] the pathologies caused by
diabetes , [ 108 ] [ 109 ] rheumatoid arthritis , [ 110 ] and
neurodegeneration in motor neuron diseases . [ 111 ] In many of
these cases, it is unclear if oxidants trigger the disease, or if
they are produced as a secondary consequence of the disease and
from general tissue damage; [ 12 ] One case in which this link is
particularly well-understood is the role of oxidative stress in
cardiovascular disease . Here, low density lipoprotein (LDL)
oxidation appears to trigger the process of atherogenesis , which
results in atherosclerosis , and finally cardiovascular disease. [
112 ] [ 113 ]
A low calorie diet extends median and maximum lifespan in many
animals. This effect may involve a reduction in oxidative stress. [
114 ] While there is some evidence to support the role of oxidative
stress in aging in model organisms such as Drosophila melanogaster
and Caenorhabditis elegans , [ 115 ] [ 116 ] the evidence in
mammals is less clear. [ 117 ] [ 118 ] [ 119 ] Indeed, a 2009
review of experiments in mice concluded that almost all
manipulations of antioxidant systems had no effect on aging. [ 120
] Diets high in fruit and vegetables, which are high in
antioxidants, promote health and reduce the effects of aging,
however antioxidant vitamin supplementation has no detectable
effect on the aging process, so the effects of fruit and vegetables
may be unrelated to their antioxidant contents. [ 121 ] [ 122 ] One
reason for this might be the fact that consuming antioxidant
molecules such as polyphenols and vitamin E will produce changes in
other parts of metabolism, so it may be these other effects that
are the real reason these compounds are important in human
nutrition. [ 64 ] [ 123 ]
Health effects
Disease treatment
The brain is uniquely vulnerable to oxidative injury, due to its
high metabolic rate and elevated levels of polyunsaturated lipids,
the target of lipid peroxidation. [ 124 ] Consequently,
antioxidants are commonly used as medications to treat various
forms of brain injury. Here, superoxide dismutase mimetics, [ 125 ]
sodium thiopental and propofol are used to treat reperfusion injury
and traumatic brain injury , [ 126 ] while the experimental drug
NXY-059 [ 127 ] [ 128 ] and ebselen [ 129 ] are being applied in
the treatment of stroke. These compounds appear to prevent
oxidative stress in neurons and prevent apoptosis and neurological
damage. Antioxidants are also being investigated as possible
treatments for neurodegenerative diseases such as Alzheimer's
disease , Parkinson's disease , and amyotrophic lateral sclerosis ,
[ 130 ] [ 131 ] and as a way to prevent noise-induced hearing loss
. [ 132 ]
Disease prevention
Structure of the polyphenol antioxidant resveratrol .
People who eat fruits and vegetables have a lower risk of heart
disease and some neurological diseases, [ 133 ] and there is
evidence that some types of vegetables, and fruits in general,
protect against some cancers. [ 134 ] Since fruits and vegetables
happen to be good sources of antioxidants, this suggested that
antioxidants might prevent some types of diseases. This idea has
been tested in clinical trials and does not seem to be true, as
antioxidant supplements have no clear effect on the risk of chronic
diseases such as cancer and heart disease. [ 133 ] [ 135 ] This
suggests that these health benefits come from other substances in
fruits and vegetables (possibly flavonoids ), or come from a
complex mix of substances. [ 136 ] [ 137 ]
It is thought that oxidation of low density lipoprotein in the
blood contributes to heart disease, and initial observational
studies found that people taking Vitamin E supplements had a lower
risk of developing heart disease. [ 138 ] Consequently, at least
seven large clinical trials were conducted to test the effects of
antioxidant supplement with Vitamin E, in doses ranging from 50 to
600 mg per day. None of these trials found a statistically
significant effect of Vitamin E on overall number of deaths or on
deaths due to heart disease. [ 139 ] Further studies have also been
negative. [ 140 ] [ 141 ] It is not clear if the doses used in
these trials or in most dietary supplements are capable of
producing any significant decrease in oxidative stress. [ 142 ]
Overall, despite the clear role of oxidative stress in
cardiovascular disease, controlled studies using antioxidant
vitamins have observed no reduction in either the risk of
developing heart disease, or the rate of progression of existing
disease. [ 143 ] [ 144 ]
While several trials have investigated supplements with high doses
of antioxidants, the " Supplémentation en Vitamines et
Mineraux Antioxydants " (SU.VI.MAX) study tested the effect of
supplementation with doses comparable to those in a healthy diet .
[ 145 ] Over 12,500 French men and women took either low-dose
antioxidants ( 120 mg of ascorbic acid, 30 mg of vitamin E, 6 mg of
beta carotene, 100 μ g of selenium, and 20 mg of zinc) or
placebo pills for an average of 7.5 years. The investigators found
there was no statistically significant effect of the antioxidants
on overall survival, cancer, or heart disease. In a post-hoc
analysis they found a 31% reduction in the risk of cancer in men,
but not women.
Many nutraceutical and health food companies sell formulations of
antioxidants as dietary supplements and these are widely used in
industrialized countries . [ 146 ] These supplements may include
specific antioxidant chemicals, like the polyphenol , resveratrol
(from grape seeds or knotweed roots), [ 147 ] combinations of
antioxidants, like the "ACES" products that contain beta carotene
(provitamin A ), vitamin C , vitamin E and S elenium, or herbs that
contain antioxidants - such as green tea and jiaogulan . Although
some levels of antioxidant vitamins and minerals in the diet are
required for good health, there is considerable doubt as to whether
these antioxidant supplements are beneficial or harmful, and if
they are actually beneficial, which antioxidant(s) are needed and
in what amounts. [ 133 ] [ 135 ] [ 148 ] Indeed, some authors argue
that the hypothesis that antioxidants could prevent chronic
diseases has now been disproved and that the idea was misguided
from the beginning. [ 149 ] Rather, dietary polyphenols may have
non-antioxidant roles in minute concentrations that affect
cell-to-cell signaling, receptor sensitivity, inflammatory enzyme
activity or gene regulation . [ 150 ] [ 151 ]
For overall life expectancy , it has even been suggested that
moderate levels of oxidative stress may increase lifespan in the
worm Caenorhabditis elegans , by inducing a protective response to
increased levels of reactive oxygen species. [ 152 ] The suggestion
that increased life expectancy comes from increased oxidative
stress conflicts with results seen in the yeast Saccharomyces
cerevisiae , [ 153 ] and the situation in mammals is even less
clear. [ 117 ] [ 118 ] [ 119 ] Nevertheless, antioxidant
supplements do not appear to increase life expectancy in humans. [
154 ]
Physical exercise
During exercise, oxygen consumption can increase by a factor of
more than 10. [ 155 ] This leads to a large increase in the
production of oxidants and results in damage that contributes to
muscular fatigue during and after exercise. The inflammatory
response that occurs after strenuous exercise is also associated
with oxidative stress, especially in the 24 hours after an exercise
session. The immune system response to the damage done by exercise
peaks 2 to 7 days after exercise, which is the period during which
most of the adaptation that leads to greater fitness occurs. During
this process, free radicals are produced by neutrophils to remove
damaged tissue. As a result, excessive antioxidant levels may
inhibit recovery and adaptation mechanisms. [ 156 ] Antioxidant
supplements may also prevent any of the health gains that normally
come from exercise, such as increased insulin sensitivity . [ 157
]
The evidence for benefits from antioxidant supplementation in
vigorous exercise is mixed. There is strong evidence that one of
the adaptations resulting from exercise is a strengthening of the
body's antioxidant defenses, particularly the glutathione system,
to regulate the increased oxidative stress. [ 158 ] This effect may
be to some extent protective against diseases which are associated
with oxidative stress, which would provide a partial explanation
for the lower incidence of major diseases and better health of
those who undertake regular exercise. [ 159 ]
However, no benefits for physical performance to athletes are seen
with vitamin E supplementation. [ 160 ] Indeed, despite its key
role in preventing lipid membrane peroxidation, 6 weeks of vitamin
E supplementation had no effect on muscle damage in ultramarathon
runners. [ 161 ] Although there appears to be no increased
requirement for vitamin C in athletes, there is some evidence that
vitamin C supplementation increased the amount of intense exercise
that can be done and vitamin C supplementation before strenuous
exercise may reduce the amount of muscle damage. [ 162 ] [ 163 ]
However, other studies found no such effects, and some research
suggests that supplementation with amounts as high as 1000 mg
inhibits recovery. [ 164 ]
Adverse effects
Further information: Micronutrients
Structure of the metal chelator phytic acid .
Relatively strong reducing acids can have antinutrient effects by
binding to dietary minerals such as iron and zinc in the
gastrointestinal tract and preventing them from being absorbed. [
165 ] Notable examples are oxalic acid , tannins and phytic acid ,
which are high in plant-based diets. [ 166 ] Calcium and iron
deficiencies are not uncommon in diets in developing countries
where less meat is eaten and there is high consumption of phytic
acid from beans and unleavened whole grain bread. [ 167 ]
Foods
Reducing acid present
Cocoa bean and chocolate , spinach , turnip and rhubarb . [ 168
]
Oxalic acid
Nonpolar antioxidants such as eugenol —a major component of
oil of cloves —have toxicity limits that can be exceeded with
the misuse of undiluted essential oils . [ 171 ] Toxicity
associated with high doses of water-soluble antioxidants such as
ascorbic acid are less of a concern, as these compounds can be
excreted rapidly in urine . [ 172 ] More seriously, very high doses
of some antioxidants may have harmful long-term effects. The
beta-Carotene and Retinol Efficacy Trial (CARET) study of lung
cancer patients found that smokers given supplements containing
beta-carotene and vitamin A had increased rates of lung cancer. [
173 ] Subsequent studies confirmed these adverse effects. [ 174
]
These harmful effects may also be seen in non-smokers, as a recent
meta-analysis including data from approximately 230,000 patients
showed that β-carotene, vitamin A or vitamin E supplementation
is associated with increased mortality but saw no significant
effect from vitamin C. [ 175 ] No health risk was seen when all the
randomized controlled studies were examined together, but an
increase in mortality was detected only when the high-quality and
low-bias risk trials were examined separately. However, as the
majority of these low-bias trials dealt with either elderly people
, or people already suffering disease, these results may not apply
to the general population. [ 176 ] This meta-analysis was later
repeated and extended by the same authors, with the new analysis
published by the Cochrane Collaboration ; confirming the previous
results. [ 177 ] These two publications are consistent with some
previous meta-analyzes that also suggested that Vitamin E
supplementation increased mortality, [ 178 ] and that antioxidant
supplements increased the risk of colon cancer . [ 179 ] However,
the results of this meta-analysis are inconsistent with other
studies such as the SU.VI.MAX trial, which suggested that
antioxidants have no effect on cause-all mortality. [ 145 ] [ 180 ]
[ 181 ] [ 182 ] Overall, the large number of clinical trials
carried out on antioxidant supplements suggest that either these
products have no effect on health, or that they cause a small
increase in mortality in elderly or vulnerable populations. [ 133 ]
[ 135 ] [ 175 ]
While antioxidant supplementation is widely used in attempts to
prevent the development of cancer, it has been proposed that
antioxidants may, paradoxically, interfere with cancer treatments.
[ 183 ] This was thought to occur since the environment of cancer
cells causes high levels of oxidative stress, making these cells
more susceptible to the further oxidative stress induced by
treatments. As a result, by reducing the redox stress in cancer
cells, antioxidant supplements could decrease the effectiveness of
radiotherapy and chemotherapy . [ 184 ] [ 185 ] On the other hand,
other reviews have suggested that antioxidants could reduce side
effects or increase survival times. [ 186 ] [ 187 ]
Measurement and levels in food
Further information: List of antioxidants in food , Polyphenol
antioxidants
Fruits and vegetables are good sources of antioxidants.
Measurement of antioxidants is not a straightforward process, as
this is a diverse group of compounds with different reactivities to
different reactive oxygen species. In food science , the oxygen
radical absorbance capacity (ORAC) has become the current industry
standard for assessing antioxidant strength of whole foods, juices
and food additives. [ 188 ] [ 189 ] Other measurement tests include
the Folin-Ciocalteu reagent , and the Trolox equivalent antioxidant
capacity assay. [ 190 ]
Antioxidants are found in varying amounts in foods such as
vegetables, fruits, grain cereals, eggs, meat, legumes and nuts.
Some antioxidants such as lycopene and ascorbic acid can be
destroyed by long-term storage or prolonged cooking. [ 191 ] [ 192
] Other antioxidant compounds are more stable, such as the
polyphenolic antioxidants in foods such as whole-wheat cereals and
tea. [ 193 ] [ 194 ] The effects of cooking and food processing are
complex, as these processes can also increase the bioavailability
of antioxidants, such as some carotenoids in vegetables. [ 195 ] In
general, processed foods contain fewer antioxidants than fresh and
uncooked foods, since the preparation processes may expose the food
to oxygen. [ 196 ]
Antioxidant compounds
Foods containing high levels of these antioxidants [ 170 ] [ 197 ]
[ 198 ]
Vitamin C (ascorbic acid)
Fruits and vegetables
Vitamin E (tocopherols, tocotrienols)
Vegetable oils
Polyphenolic antioxidants ( resveratrol , flavonoids )
Tea, coffee , soy , fruit , olive oil , chocolate , cinnamon ,
oregano and red wine
Other antioxidants are not vitamins and are instead made in the
body. For example, ubiquinol (coenzyme Q) is poorly absorbed from
the gut and is made in humans through the mevalonate pathway . [ 42
] Another example is glutathione , which is made from amino acids.
As any glutathione in the gut is broken down to free cysteine,
glycine and glutamic acid before being absorbed, even large oral
doses have little effect on the concentration of glutathione in the
body. [ 200 ] [ 201 ] Although large amounts of sulfur-containing
amino acids such as acetylcysteine can increase glutathione, [ 202
] no evidence exists that eating high levels of these glutathione
precursors is beneficial for healthy adults. [ 203 ] Supplying more
of these precursors may be useful as part of the treatment of some
diseases, such as acute respiratory distress syndrome ,
protein-energy malnutrition , or preventing the liver damage
produced by paracetamol overdose. [ 202 ] [ 204 ]
Other compounds in the diet can alter the levels of antioxidants by
acting as pro-oxidants . Here, consuming the compound causes
oxidative stress, which the body responds to by inducing higher
levels of antioxidant defenses such as antioxidant enzymes. [ 149 ]
Some of these compounds, such as isothiocyanates and curcumin , may
be chemopreventive agents that either block the transformation of
abnormal cells into cancerous cells, or even kill existing cancer
cells. [ 149 ] [ 205 ]
Uses in technology
Food preservatives
Antioxidants are used as food additives to help guard against food
deterioration . Exposure to oxygen and sunlight are the two main
factors in the oxidation of food, so food is preserved by keeping
in the dark and sealing it in containers or even coating it in wax,
as with cucumbers. However, as oxygen is also important for plant
respiration , storing plant materials in anaerobic conditions
produces unpleasant flavors and unappealing colors. [ 206 ]
Consequently, packaging of fresh fruits and vegetables contains an
~8% oxygen atmosphere. Antioxidants are an especially important
class of preservatives as, unlike bacterial or fungal spoilage,
oxidation reactions still occur relatively rapidly in frozen or
refrigerated food. [ 207 ] These preservatives include natural
antioxidants such as ascorbic acid (AA, E300) and tocopherols
(E306), as well as synthetic antioxidants such as propyl gallate
(PG, E310), tertiary butylhydroquinone (TBHQ), butylated
hydroxyanisole (BHA, E320) and butylated hydroxytoluene (BHT,
E321). [ 208 ] [ 209 ]
The most common molecules attacked by oxidation are unsaturated
fats; oxidation causes them to turn rancid . [ 210 ] Since oxidized
lipids are often discolored and usually have unpleasant tastes such
as metallic or sulfurous flavors, it is important to avoid
oxidation in fat-rich foods. Thus, these foods are rarely preserved
by drying; instead, they are preserved by smoking , salting or
fermenting . Even less fatty foods such as fruits are sprayed with
sulfurous antioxidants prior to air drying. Oxidation is often
catalyzed by metals, which is why fats such as butter should never
be wrapped in aluminium foil or kept in metal containers. Some
fatty foods such as olive oil are partially protected from
oxidation by their natural content of antioxidants, but remain
sensitive to photooxidation. [ 211 ] Antioxidant preservatives are
also added to fat-based cosmetics such as lipstick and moisturizers
to prevent rancidity.
Industrial uses
Antioxidants are frequently added to industrial products. A common
use is as stabilizers in fuels and lubricants to prevent oxidation,
and in gasolines to prevent the polymerization that leads to the
formation of engine-fouling residues. [ 212 ]
They are widely used to prevent the oxidative degradation of
polymers such as rubbers , plastics and adhesives that causes a
loss of strength and flexibility in these materials. [ 213 ]
Polymers containing double bonds in their main chains are
especially susceptible to oxidation and ozonolysis . Solid polymer
products start to crack on exposed surfaces as the material
degrades and the chains unzip. The mode of cracking varies between
oxygen and ozone attack, the former causing a "crazy paving"
effect, while ozone attack produces deeper cracks aligned at right
angles to the tensile strain in the product. Ozone cracking is
especially damaging to elastomers such as natural rubber ,
polybutadiene and other double-bonded rubbers. They can be
protected by antiozonants . Oxidation and UV degradation are also
frequently linked, mainly because UV radiation creates free
radicals by bond breakage. The free radicals then react with oxygen
to produce peroxy radicals which cause yet further damage, often in
a chain reaction . Other polymers suceptible to oxidation include
polypropylene and polyethylene . The former is more sensitive owing
to the presence of secondary carbon atoms present in every repeat
unit. Attack occurs at this point because the free radical formed
is more stable than one formed on a primary carbon atom . Oxidation
of polyethylene tends to occur at weak links in the chain, such as
branch points in low density polyethylene .
In chemistry , an alkali (from Arabic : Al-Qaly
القلي,
القالي ) is a basic , ionic
salt of an alkali metal or alkaline earth metal element . Alkalis
are best known for being bases that dissolve in water . Bases are
compounds with a pH greater than 7. The adjective alkaline is
commonly used in English as a synonym for base, especially for
soluble bases. This broad use of the term is likely to have come
about because alkalis were the first bases known to obey the
Arrhenius definition of a base and are still among the more common
bases. Since Brønsted-Lowry acid-base theory , the term
alkali in chemistry is normally restricted to those salts
containing alkali and alkaline earth metal elements.
Contents
1 Etymology
2 Common properties
3 Confusion between alkali and base
4 Salts
5 Alkaline soil
6 Lakes
7 References
//
Etymology
The word "alkali" is derived from Arabic al qalīy = the
calcined ashes , referring to the original source of alkaline
substance. Ashes were used in conjunction with animal fat to
produce soap , a process known as saponification .
Common properties
Alkalis are all Arrhenius bases, which form hydroxide ions (OH - )
when dissolved in water. Common properties of alkaline aqueous
solutions include:
Moderately-concentrated solutions (over 10 −3 M) have a pH of
7.1 or greater. This means that they will turn phenolphthalein from
colorless to pink.
Concentrated solutions are caustic (causing chemical burns).
Alkaline solutions are slippery or soapy to the touch, due to the
saponification of the fatty acids on the surface of the skin.
Alkalis are normally water soluble , although some like barium
carbonate are only soluble when reacting with an acidic aqueous
solution.
Acids and alkalis are measured on a pH scale
Alkalis are commonly found in household cleaners and toothpaste
Confusion between alkali and base
The terms "base" and "alkali" are often used interchangeably,
particularly outside of a scientific context, but they do not have
the same meaning. While all alkaline solutions are basic, not all
bases are alkaline. The following are common mistakes:
The phrase "measuring the alkalinity of soil" is incorrect since
the property measured is actually the pH (base property).
Calling bases that are not alkalis, such as ammonia , alkaline
(ammonia is a base but not an alkali).
Also, not all salts formed by alkali metals are alkaline; this
designation applies only to those salts that are basic. And while
most electropositive metal oxides are basic, only the soluble
alkali metal and alkaline earth metal oxides can be correctly
called alkalis.
This definition of an alkali as a basic salt of an alkali metal or
alkaline earth metal is the most common, based on dictionary
definitions [1] [2] , however conflicting definitions of the term
alkali do exist. These include:
Any base that is water-soluble and forms hydroxide ions [3] [4] .
In chemistry, this is more accurately called an Arrhenius base
.
The solution of a base in water [5] . This would be an Arrhenius
base in solution.
Name given by chemists to an important group of subtances, the
behaviour of bases the main alkali are 1,the hydroxides potassium
2,
Salts
Most basic salts are alkali salts, of which common examples
are:
sodium hydroxide (often called "caustic soda")
potassium hydroxide (commonly called "caustic potash")
lye (generic term, for either of the previous two, or even for a
mixture)
calcium carbonate (sometimes called "free lime")
magnesium hydroxide is an example of an atypical alkali since it
has low solubility in water (although the dissolved portion is
considered a strong base due to complete dissociation of its
ions).
Alkaline soil
Soil with a pH value higher than 7.3 is normally referred to as
alkaline. This soil property can occur naturally, due to the
presence of alkali salts. Although some plants do prefer slightly
basic soil (including vegetables like cabbage and fodder like
buffalograss ), most plants prefer a mildly acidic soil (pH between
6.0 and 6.8), and alkaline soils can cause problems.
Lakes
In alkali lakes (a type of salt lake ), evaporation concentrates
the naturally-occurring alkali salts, often forming a crust of
mildly-basic salt across a large area.
Examples of alkali lakes:
Redberry Lake, Saskatchewan , Canada .
Tramping Lake, Saskatchewan , Canada.
Mono lake , California , United States
Summer Lake , Oregon , United States
Alkali Lake, British Columbia and the adjoining reserves of the
Alkali Lake Indian Band are named for a local Alkali Lake, which
got its name from a large patch of alkali on the hillside above the
lake, which is not itself alkali, [ 1 ] although there are many in
the Cariboo district and adjoining regions of the British Columbia
Interior .
A water ionizer is an appliance that ionizes water . Ionized water
is purported to be beneficial to human health and marketed with
claims that it is an antioxidant which can slow aging and prevent
disease. [ 1 ] Others note that such claims contradict basic laws
of chemistry and physiology. [ 2 ]
Contents
1 Ionization
2 Uses
3 See also
4 References
5 External links
//
Ionization
Main article: Electrolysis of water
A water ionizer separates water into alkaline and acid fractions
using a process known as electrolysis . [ 3 ] It does this by
exploiting the electric charge of the calcium and magnesium ions
present in nearly all sources of drinking water. When a source of
water lacks mineral ions, such as distilled water , or has been
filtered by reverse osmosis , water ionization has no effect.
Uses
Some research suggests that alkaline reduced water may be useful in
scavenging free radicals in the laboratory setting. [ 4 ] Tests on
in vitro lymphocytes suggest that reduced water can prevent
hydrogen peroxide -induced damage to DNA , RNA and certain proteins
. [ 5 ] However, drinking ionized water would not be expected to
alter the body's pH , and there is no evidence of any claims made
by manufacturers that drinking ionized water will have a noticeable
effect on the body. [ 2 ]
Electrolyzed water has been used by the food industry to sanitize
food products; though effective in bacterial solutions, it was
found less useful when sanitizing utensils, surfaces and food
products. [ 6 ] [ 7 ] Acidic electrolyzed water (pH 2.3–2.6)
may have use as a seed surface disinfectant or contact bactericide
. [ 8 ]
Health insurance like other forms of insurance is a form of
collectivism by means of which people collectively pool their risk,
in this case the risk of incurring medical expenses. It is
sometimes used more broadly to include insurance covering
disability or long-term nursing or custodial care needs. It may be
provided through a government-sponsored social insurance program,
or from private insurance companies. It may be purchased on a group
basis (e.g., by a firm to cover its employees) or purchased by
individual consumers. In each case, the covered groups or
individuals pay premiums or taxes to help protect themselves from
high or unexpected healthcare expenses. Similar benefits paying for
medical expenses may also be provided through social welfare
programs funded by the government.
By estimating the overall risk of healthcare expenses, a routine
finance structure (such as a monthly premium or annual tax) can be
developed, ensuring that money is available to pay for the
healthcare benefits specified in the insurance agreement. The
benefit is administered by a central organization such as a
government agency, private business, or not-for-profit entity. [ 1
]
Contents
1 History and evolution
2 How it works
2.1 Health plan vs. health insurance
2.2 Comprehensive vs. scheduled
2.3 Other factors affecting insurance prices
3 Comparison
3.1 Australia
3.2 Canada
3.3 France
3.4 Netherlands
3.5 United Kingdom
3.6 United States
3.6.1 California
3.7 Germany
3.7.1 Insurance systems
4 See also
5 Notes and references
//
History and evolution
Main article: History of insurance
The concept of health insurance was proposed in 1694 by Hugh the
Elder Chamberlen from the Peter Chamberlen family. In the late 19th
century, "accident insurance" began to be available, which operated
much like modern disability insurance. [ 2 ] [ 3 ] This payment
model continued until the start of the 20th century in some
jurisdictions (like California), where all laws regulating health
insurance actually referred to disability insurance. [ 4 ]
Accident insurance was first offered in the United States by the
Franklin Health Assurance Company of Massachusetts. This firm,
founded in 1850, offered insurance against injuries arising from
railroad and steamboat accidents. Sixty organizations were offering
accident insurance in the U.S. by 1866, but the industry
consolidated rapidly soon thereafter. While there were earlier
experiments, the origins of sickness coverage in the U.S.
effectively date from 1890. The first employer-sponsored group
disability policy was issued in 1911. [ 5 ]
Before the development of medical expense insurance, patients were
expected to pay all other health care costs out of their own
pockets, under what is known as the fee-for-service business model.
During the middle to late 20th century, traditional disability
insurance evolved into modern health insurance programs. Today,
most comprehensive private health insurance programs cover the cost
of routine, preventive, and emergency health care procedures, and
most prescription drugs, but this was not always the case.
Hospital and medical expense policies were introduced during the
first half of the 20th century. During the 1920s, individual
hospitals began offering services to individuals on a pre-paid
basis, eventually leading to the development of Blue Cross
organizations. [ 5 ] The predecessors of today's Health Maintenance
Organizations (HMOs) originated beginning in 1929, through the
1930s and on during World War II . [ 6 ] [ 7 ]
How it works
A health insurance policy is a contract between an insurance
company and an individual or his sponsor (e.g. an employer). The
contract can be renewable annually or monthly. The type and amount
of health care costs that will be covered by the health insurance
company are specified in advance, in the member contract or
"Evidence of Coverage" booklet. The individual insured person's
obligations may take several forms: [ 8 ]
Premium: The amount the policy-holder or his sponsor (e.g. an
employer) pays to the health plan each month to purchase health
coverage.
Deductible : The amount that the insured must pay out-of-pocket
before the health insurer pays its share. For example, a
policy-holder might have to pay a $500 deductible per year, before
any of their health care is covered by the health insurer. It may
take several doctor's visits or prescription refills before the
insured person reaches the deductible and the insurance company
starts to pay for care.
Co-payment : The amount that the insured person must pay out of
pocket before the health insurer pays for a particular visit or
service. For example, an insured person might pay a $45 co-payment
for a doctor's visit, or to obtain a prescription. A co-payment
must be paid each time a particular service is obtained.
Coinsurance : Instead of, or in addition to, paying a fixed amount
up front (a co-payment), the co-insurance is a percentage of the
total cost that insured person may also pay. For example, the
member might have to pay 20% of the cost of a surgery over and
above a co-payment, while the insurance company pays the other 80%.
If there is an upper limit on coinsurance, the policy-holder could
end up owing very little, or a great deal, depending on the actual
costs of the services they obtain.
Exclusions: Not all services are covered. The insured person is
generally expected to pay the full cost of non-covered services out
of their own pocket.
Coverage limits: Some health insurance policies only pay for health
care up to a certain dollar amount. The insured person may be
expected to pay any charges in excess of the health plan's maximum
payment for a specific service. In addition, some insurance company
schemes have annual or lifetime coverage maximums. In these cases,
the health plan will stop payment when they reach the benefit
maximum, and the policy-holder must pay all remaining costs.
Out-of-pocket maximums: Similar to coverage limits, except that in
this case, the insured person's payment obligation ends when they
reach the out-of-pocket maximum, and the health company pays all
further covered costs. Out-of-pocket maximums can be limited to a
specific benefit category (such as prescription drugs) or can apply
to all coverage provided during a specific benefit year.
Capitation : An amount paid by an insurer to a health care
provider, for which the provider agrees to treat all members of the
insurer.
In-Network Provider: (U.S. term) A health care provider on a list
of providers preselected by the insurer. The insurer will offer
discounted coinsurance or co-payments, or additional benefits, to a
plan member to see an in-network provider. Generally, providers in
network are providers who have a contract with the insurer to
accept rates further discounted from the "usual and customary"
charges the insurer pays to out-of-network providers.
Prior Authorization: A certification or authorization that an
insurer provides prior to medical service occurring. Obtaining an
authorization means that the insurer is obligated to pay for the
service, assuming it matches what was authorized. Many smaller,
routine services do not require authorization. [ 9 ]
Explanation of Benefits : A document sent by an insurer to a
patient explaining what was covered for a medical service, and how
they arrived at the payment amount and patient responsibility
amount. [ 10 ]
Prescription drug plans are a form of insurance offered through
some employer benefit plans in the U.S., where the patient pays a
copayment and the prescription drug insurance part or all of the
balance for drugs covered in the formulary of the plan.
Some, if not most, health care providers in the United States will
agree to bill the insurance company if patients are willing to sign
an agreement that they will be responsible for the amount that the
insurance company doesn't pay. The insurance company pays out of
network providers according to "reasonable and customary" charges,
which may be less than the provider's usual fee. The provider may
also have a separate contract with the insurer to accept what
amounts to a discounted rate or capitation to the provider's
standard charges. It generally costs the patient less to use an
in-network provider.
Health plan vs. health insurance
Historically, HMOs tended to use the term "health plan", while
commercial insurance companies used the term "health insurance". A
health plan can also refer to a subscription -based medical care
arrangement offered through HMOs , preferred provider organizations
, or point of service plans . These plans are similar to pre-paid
dental, pre-paid legal, and pre-paid vision plans. Pre-paid health
plans typically pay for a fixed number of services (for instance,
$300 in preventive care, a certain number of days of hospice care
or care in a skilled nursing facility, a fixed number of home
health visits, a fixed number of spinal manipulation charges, etc.)
The services offered are usually at the discretion of a utilization
review nurse who is often contracted through the managed care
entity providing the subscription health plan. This determination
may be made either prior to or after hospital admission (concurrent
utilization review).
Comprehensive vs. scheduled
Comprehensive health insurance pays a percentage of the cost of
hospital and physician charges after a deductible (usually applies
to hospital charges) or a co-pay (usually applies to physician
charges, but may apply to some hospital services) is met by the
insured. These plans are generally expensive because of the high
potential benefit payout — $1,000,000 to 5,000,000 is common
— and because of the vast array of covered benefits. [ 11
]
Scheduled health insurance plans are not meant to replace a
traditional comprehensive health insurance plans and are more of a
basic policy providing access to day-to-day health care such as
going to the doctor or getting a prescription drug. In recent
years, these plans have taken the name mini-med plans or
association plans. The term "association" is often used to describe
them because they require membership in an association that must
exist for some other purpose than to sell insurance. Examples
include the National Association for the Self Employed and the
Health Care Credit Union Association . These plans may provide
benefits for hospitalization and surgical, but these benefits will
be limited. Scheduled plans are not meant to be effective for
catastrophic events. These plans cost much less than comprehensive
health insurance. They generally pay limited benefits amounts
directly to the service provider, and payments are based upon the
plan's "schedule of benefits". Annual benefits maximums for a
typical scheduled health insurance plan may range from $1,000 to
$25,000. [ 12 ]
Other factors affecting insurance prices
A recent study by PriceWaterhouseCoopers examining the drivers of
rising health care costs in the U.S. pointed to increased
utilization created by increased consumer demand, new treatments,
and more intensive diagnostic testing, as the most significant
driver. [ 13 ] People in developed countries are living longer. The
population of those countries is aging, and a larger group of
senior citizens requires more intensive medical care than a young
healthier population. Advances in medicine and medical technology
can also increase the cost of medical treatment. Lifestyle-related
factors can increase utilization and therefore insurance prices,
such as: increases in obesity caused by insufficient exercise and
unhealthy food choices ; excessive alcohol use, smoking , and use
of street drugs . Other factors noted by the PWC study included the
movement to broader-access plans, higher-priced technologies, and
cost-shifting from Medicaid and the uninsured to private payers. [
13 ]
Comparison
See also: Health care systems
The Commonwealth Fund, in its annual survey, "Mirror, Mirror on the
Wall", compares the performance of the health care systems in
Australia, New Zealand, the United Kingdom, Germany, Canada and the
U.S. Its 2007 study found that, although the U.S. system is the
most expensive, it consistently under-performs compared to the
other countries. [ 14 ] One difference between the U.S. and the
other countries in the study is that the U.S. is the only country
without universal health insurance coverage.
Australia
Main article: Health care in Australia
The public health system is called Medicare . It ensures free
universal access to hospital treatment and subsidised
out-of-hospital medical treatment. It is funded by a 1.5% tax levy
on all taxpayers, an extra 1% levy on high income earners, as well
as general revenue.
The private health system is funded by a number of private health
insurance organisations. The largest of these is Medibank Private,
which is government-owned, but operates as a government business
enterprise under the same regulatory regime as all other registered
private health funds. The Coalition Howard government had announced
that Medibank would be privatised if it won the 2007 election,
however they were defeated by the Australian Labor Party under
Kevin Rudd which had already pledged that it would remain in
government ownership.
Some private health insurers are 'for profit' enterprises, and some
are non-profit organizations such as HCF Health Insurance and GMHBA
Health Insurance . Some have membership restricted to particular
groups, but the majority have open membership. Membership to most
health funds is now also available through comparison websites like
moneytime , iSelect or the decision assistance site HelpMeChoose .
These comparison sites operate on a commission-basis by agreement
with their participating health funds.
Most aspects of private health insurance in Australia are regulated
by the Private Health Insurance Act 2007 .
The private health system in Australia operates on a "community
rating" basis, whereby premiums do not vary solely because of a
person's previous medical history, current state of health, or
(generally speaking) their age (but see Lifetime Health Cover
below). Balancing this are waiting periods, in particular for
pre-existing conditions (usually referred to within the industry as
PEA, which stands for "pre-existing ailment"). Funds are entitled
to impose a waiting period of up to 12 months on benefits for any
medical condition the signs and symptoms of which existed during
the six months ending on the day the person first took out
insurance. They are also entitled to impose a 12-month waiting
period for benefits for treatment relating to an obstetric
condition, and a 2-month waiting period for all other benefits when
a person first takes out private insurance. Funds have the
discretion to reduce or remove such waiting periods in individual
cases. They are also free not to impose them to begin with, but
this would place such a fund at risk of "adverse selection",
attracting a disproportionate number of members from other funds,
or from the pool of intending members who might otherwise have
joined other funds. It would also attract people with existing
medical conditions, who might not otherwise have taken out
insurance at all because of the denial of benefits for 12 months
due to the PEA Rule. The benefits paid out for these conditions
would create pressure on premiums for all the fund's members,
causing some to drop their membership, which would lead to further
rises in premiums, and a vicious cycle of higher premiums-leaving
members would ensue.
There are a number of other matters about which funds are not
permitted to discriminate between members in terms of premiums,
benefits or membership - these include racial origin, religion,
sex, sexual orientation, nature of employment, and leisure
activities. Premiums for a fund's product that is sold in more than
one state can vary from state to state, but not within the same
state.
The Australian government has introduced a number of incentives to
encourage adults to take out private hospital insurance. These
include:
Lifetime Health Cover : If a person has not taken out private
hospital cover by the 1st July after their 31st birthday, then when
(and if) they do so after this time, their premiums must include a
loading of 2% per annum for each year they were without hospital
cover. Thus, a person taking out private cover for the first time
at age 40 will pay a 20 per cent loading. The loading is removed
after 10 years of continuous hospital cover. The loading applies
only to premiums for hospital cover, not to ancillary (extras)
cover.
Medicare Levy Surcharge : People whose taxable income is greater
than a specified amount (currently $70,000 for singles and $140,000
for couples) and who do not have an adequate level of private
hospital cover must pay a 1% surcharge on top of the standard 1.5%
Medicare Levy. The rationale is that if the people in this income
group are forced to pay more money one way or another, most would
choose to purchase hospital insurance with it, with the possibility
of a benefit in the event that they need private hospital treatment
- rather than pay it in the form of extra tax as well as having to
meet their own private hospital costs.
The Australian government announced in May 2008 that it proposes to
increase the thresholds, to $100,000 for singles and $150,000 for
families. These changes require legislative approval. A bill to
change the law has been introduced but was not passed by the
Senate. [ 15 ] [ 16 ] An amended version was passed on
16 October 2008. There have been criticisms that the changes
will cause many people to drop their private health insurance,
causing a further burden on the public hospital system, and a rise
in premiums for those who stay with the private system. Other
commentators believe the effect will be minimal. [ 17 ]
Private Health Insurance Rebate : The government subsidises the
premiums for all private health insurance cover, including hospital
and ancillary (extras), by 30%, 35% or 40%, depending on age. The
Rudd Government announced in May 2009 that as of July 2010, the
Rebate would become means-tested, and offered on a sliding
scale.
Canada
Main article: Health care in Canada
Most health insurance in Canada is administered by each province,
under the Canada Health Act , which requires all people to have
free access to health care. Collectively, the public provincial
health insurance systems in Canada are frequently referred to as
Medicare . Private health insurance is allowed, but the provincial
governments allow it only for services that the public health plans
do not cover; for example, semi-private or private rooms in
hospitals and prescription drug plans. Canadians are free to use
private insurance for elective medical services such as laser
vision correction surgery, cosmetic surgery, and other non-basic
medical procedures. Some 65% of Canadians have some form of
supplementary private health insurance; many of them receive it
through their employers. [ 18 ] Private-sector services not paid
for by the government account for nearly 30 percent of total health
care spending. [ 19 ]
In 2005, the Supreme Court of Canada ruled, in Chaoulli v. Quebec ,
that the province's prohibition on private insurance for health
care already insured by the provincial plan could constitute an
infringement of the right to life and security if there were long
wait times for treatment as happened in this case. Certain other
provinces have legislation which financially discourages but does
not forbid private health insurance in areas covered by the public
plans. The ruling has not changed the overall pattern of health
insurance across Canada but has spurred on attempts to tackle the
core issues of supply and demand and the impact of wait times. [ 20
]
France
Main article: Health care in France
The national system of health insurance was instituted in 1945,
just after the end of the Second World War. It was a compromise
between Gaullist and Communist representatives in the French
parliament. The Conservative Gaullists were opposed to a state-run
healthcare system, while the Communists were supportive of a
complete nationalisation of health care along a British Beveridge
model.
The resulting programme is profession-based: all people working are
required to pay a portion of their income to a health insurance
fund, which mutualises the risk of illness, and which reimburses
medical expenses at varying rates. Children and spouses of insured
people are eligible for benefits, as well. Each fund is free to
manage its own budget, and used to reimburse medical expenses at
the rate it saw fit, however following a number of reforms in
recent years, the majority of funds provide the same level of
reimbursment and benefits.
The government has two responsibilities in this system.
The first government responsibility is the fixing of the rate at
which medical expenses should be negotiated, and it does this in
two ways: The Ministry of Health directly negotiates prices of
medicine with the manufacturers, based on the average price of sale
observed in neighboring countries. A board of doctors and experts
decides if the medicine provides a valuable enough medical benefit
to be reimbursed (note that most medicine is reimbursed, including
homeopathy). In parallel, the government fixes the reimbursment
rate for medical services: this means that a doctor is free to
charge the fee that he wishes for a consultation or an examination,
but the social security system will only reimburse it at a pre-set
rate. These tariffs are set annually through negotiation with
doctors' representative organisations.
The second government responsibility is oversight of the
health-insurance funds, to ensure that they are correctly managing
the sums they receive, and to ensure oversight of the public
hospital network.
Today, this system is more-or-less intact. All citizens and legal
foreign residents of France are covered by one of these mandatory
programs, which continue to be funded by worker participation.
However, since 1945, a number of major changes have been
introduced. Firstly, the different health-care funds (there are
five: General, Independent, Agricultural, Student, Public Servants)
now all reimburse at the same rate. Secondly, since 2000, the
government now provides health care to those who are not covered by
a mandatory regime (those who have never worked and who are not
students, meaning the very rich or the very poor). This regime,
unlike the worker-financed ones, is financed via general taxation
and reimburses at a higher rate than the profession-based system
for those who cannot afford to make up the difference. Finally, to
counter the rise in health-care costs, the government has installed
two plans, (in 2004 and 2006), which require insured people to
declare a referring doctor in order to be fully reimbursed for
specalist visits, and which installed a mandatory co-pay of 1
€ (about $1.45) for a doctor visit, 0,50 € (about 80
¢) for each box of medicine prescribed, and a fee of 16-18
€ (20-25 $) per day for hospital stays and for expensive
procedures.
An important element of the French insurance system is solidarity:
the more ill a person becomes, the less the person pays. This means
that for people with serious or chronic illnesses, the insurance
system reimburses them 100 % of expenses, and waives their
co-pay charges.
Finally, for fees that the mandatory system does not cover, there
is a large range of private complementary insurance plans
available. The market for these programs is very competitive, and
often subsidised by the employer, which means that premiums are
usually modest. 85% of French people benefit from complementary
private health insurance. [ 21 ] [ 22 ]
Netherlands
Main article: Health care in the Netherlands
In 2006, a new system of health insurance came into force in the
Netherlands. This new system avoids the two pitfalls of adverse
selection and moral hazard associated with traditional forms of
health insurance by using a combination of regulation and an
insurance equalization pool . Moral hazard is avoided by mandating
that insurance companies provide at least one policy which meets a
government set minimum standard level of coverage, and all adult
residents are obliged by law to purchase this coverage from an
insurance company of their choice. All insurance companies receive
funds from the equalization pool to help cover the cost of this
government-mandated coverage. This pool is run by a regulator which
collects salary-based contributions from employers, which make up
about 50% of all health care funding, and funding from the
government to cover people who cannot afford health care, which
makes up an additional 5%.
The remaining 45% of health care funding comes from insurance
premiums paid by the public, for which companies compete on price,
though the variation between the various competing insurers is only
about 5%. However, insurance companies are free to sell additional
policies to provide coverage beyond the national minimum. These
policies do not receive funding from the equalization pool, but
cover additional treatments, such as dental procedures and
physiotherapy, which are not paid for by the mandatory policy.
Funding from the equalization pool is distributed to insurance
companies for each person they insure under the required policy.
However, high-risk individuals get more from the pool, and
low-income persons and children under 18 have their insurance paid
for entirely. Because of this, insurance companies no longer find
insuring high risk individuals an unappealing proposition, avoiding
the potential problem of adverse selection.
Insurance companies are not allowed to have co-payments, caps, or
deductibles, or to deny coverage to any person applying for a
policy, or to charge anything other than their nationally set and
published standard premiums. Therefore, every person buying
insurance will pay the same price as everyone else buying the same
policy, and every person will get at least the minimum level of
coverage.
United Kingdom
Main article: National Health Service
The UK 's National Health Service (NHS) is a publicly funded
healthcare system that provides coverage to everyone normally
resident in the UK. It is not strictly an insurance system because
(a) there are no premiums collected, (b) costs are not charged at
the patient level and (c) costs are not pre-paid from a pool.
However, it does achieve the main aim of insurance which is to
spread financial risk arising from ill-health. The costs of running
the NHS (est. £104 billion in 2007-8) [ 23 ] are met directly
from general taxation. The NHS provides the majority of health care
in the UK, including primary care , in-patient care , long-term
health care , ophthalmology and dentistry .
Private health care has continued parallel to the NHS, paid for
largely by private insurance, but it is used by less than 8% of the
population, and generally as a top-up to NHS services. There are
many treatments that the private sector does not provide. For
example, health insurance on pregnancy is generally not covered or
covered with restricting clauses. [ 24 ] Typical exclusions for
Bupa schemes (and many other insurers) include:
ageing, menopause and puberty; AIDS/HIV; allergies or allergic
disorders; birth control, conception, sexual problems and sex
changes; chronic conditions; complications from excluded or
restricted conditions/ treatment; convalescence, rehabilitation and
general nursing care cosmetic, reconstructive or weight loss
treatment; deafness; dental/oral treatment (such as fillings, gum
disease, jaw shrinkage, etc); dialysis; drugs and dressings for
out-patient or take-home use† experimental drugs and
treatment; eyesight; HRT and bone densitometry; learning
difficulties, behavioural and developmental problems; overseas
treatment and repatriation; physical aids and devices; pre-existing
or special conditions; pregnancy and childbirth; screening and
preventive treatment; sleep problems and disorders; speech
disorders; temporary relief of symptoms. [ 25 ] († = except
in exceptional circumstances)
There are a number of other companies in the United Kingdom which
include, among others, AXA [ 26 ] , Aviva, Groupama Healthcare and
Pru Health. Similar exclusions apply, depending on the policy which
is purchased.
Recently the private sector has been used to increase NHS capacity
despite a large proportion of the British public opposing such
involvement. [ 27 ] According to the World Health Organization ,
government funding covered 86% of overall health care expenditures
in the UK as of 2004, with private expenditures covering the
remaining 14%. [ 28 ]
United States
Main articles: Health insurance in the United States , Health
insurance reform , and Health care in the United States
Today, the United States is the only westernized country with no
form of universal health insurance coverage for its citizens. In
2004, U.S. health insurers directly employed almost 470,000 people
at an average salary of $61,409. [ 29 ] (As of the fourth quarter
of 2007, the total U.S. labor force stood at 153.6 million, of whom
146.3 million were employed. Employment related to all forms of
insurance totaled 2.3 million. [ 30 ] Mean annual earnings for
full-time civilian workers as of June 2006 were $41,231; median
earnings were $33,634.) [ 31 ]
The United States health care system relies heavily on private
health insurance, which is the primary source of coverage for most
Americans. According to the CDC , approximately 58% of Americans
have private health insurance. Public programs provide the primary
source of coverage for most senior citizens and for low-income
children and families who meet certain eligibility requirements.
The primary public programs are Medicare , a federal social
insurance program for seniors and certain disabled individuals,
Medicaid , funded jointly by the federal government and states but
administered at the state level, which covers certain very low
income children and their families, and SCHIP , also a
federal-state partnership that serves certain children and families
who do not qualify for Medicaid but who cannot afford private
coverage. Other public programs include military health benefits
provided through TRICARE and the Veterans Health Administration and
benefits provided through the Indian Health Service . Some states
have additional programs for low-income individuals. [ 32 ]
A recent study found that 62 percent of all bankruptcies filed in
2007 were linked to medical expenses. Of those who filed for
bankruptcy, nearly 80 percent had health insurance. [ 33 ] In just
three years, the Medicare and Medicaid programs will account for 50
percent of all national health spending. [ 34 ] This has fueled an
outcry for an overhaul of the health care system in the United
States. The House of Representatives passed a health care reform
bill by a vote of 220-215 on November 7, 2009. [ 35 ] Currently the
fate of the bill rests on the Senate. The legislation once included
changes that would give the government the power to negotiate
policy premiums and to provide a public option, but in an effort to
acquire the necessary votes to prevent a Republican filibuster the
public option was eliminated from the bill. This would have given
citizens the option to buy into public programs like Medicare for
which current members pay only $96.40 monthly. [ 36 ] Instead the
bill now requires that all Americans purchase private health
insurance or be subject to fines. [ 37 ] [ 38 ] [ not in citation
given ] The insurance industry represents a significant lobbying
group in the United States. The major health interests have spent
an average of $1.4 million per day to lobby Congress so far this
year and are on track to spend more than half a billion dollars by
the end 2009. [ 39 ] This data may be indicative of why the current
bill no longer offers a public option.
California
In 2007, 87% of Californians had some form of health insurance. [
40 ] Services in California range from private offerings: HMOs ,
PPOs to public programs: Medi-Cal , Medicare, and Healthy Families
( SCHIP ).
At times, it is difficult to navigate the complex health insurance
system. California developed a solution to assist people across the
State and is one of the only States to have an Office devoted to
giving people tips and resources to get the best care possible.
California's Office of the Patient Advocate was established July
2000 to publish a yearly Health Care Quality Report Card on the Top
HMOs, PPOs, and Medical Groups and to create and distribute helpful
tips and resources to give Californians the tools needed to get the
best care. [ 41 ]
Additionally, California has a Help Center that assists
Californians when they have problems with their health insurance.
The Help Center is run by the Department of Managed Health Care ,
the government department that oversees and regulates HMOs and some
PPOs. The number to call is 1.888.466.2219, they have staff on hand
to help you through the process of filing a complaint, or just
figuring out what to do next.
Germany
Main article: Health care in Germany
Germany has Europe's oldest universal health care system, with
origins dating back to Otto von Bismarck 's Social legislation ,
which included the Health Insurance Bill of 1883 , Accident
Insurance Bill of 1884 , and Old Age and Disability Insurance Bill
of 1889 . As mandatory health insurance, these bills originally
applied only to low-income workers and certain government
employees; their coverage, and that of subsequent legislation
gradually expanded to cover virtually the entire population. [ 42
]
Currently 85% of the population is covered by a basic health
insurance plan provided by statute, which provides a standard level
of coverage. The remainder opt for private health insurance, which
frequently offers additional benefits. According to the World
Health Organization , Germany's health care system was 77%
government-funded and 23% privately funded as of 2004. [ 28 ]
The government partially reimburses the costs for low-wage workers,
whose premiums are capped at a predetermined value. Higher wage
workers pay a premium based on their salary. They may also opt for
private insurance, which is generally more expensive, but whose
price may vary based on the individual's health status. [ 43 ]
Reimbursement is on a fee-for-service basis, but the number of
physicians allowed to accept Statutory Health Insurance in a given
locale is regulated by the government and professional
societies.
Co payments were introduced in the 1980s in an attempt to prevent
over utilization. The average length of hospital stay in Germany
has decreased in recent years from 14 days to 9 days, still
considerably longer than average stays in the United States (5 to 6
days). [ 44 ] [ 45 ] Part of the difference is that the chief
consideration for hospital reimbursement is the number of hospital
days as opposed to procedures or diagnosis. Drug costs have
increased substantially, rising nearly 60% from 1991 through 2005.
Despite attempts to contain costs, overall health care expenditures
rose to 10.7% of GDP in 2005, comparable to other western European
nations, but substantially less than that spent in the U.S. (nearly
16% of GDP). [ 46 ]
Insurance systems
Germany has a universal multi-payer system with two main types of
health insurance. Germans are offered three mandatory health
benefits, which are co-financed by employer and employee: health
insurance, accident insurance, and long-term care insurance.
Accident insurance (Unfallversicherung) is covered by the employer
and basically covers all risks for commuting to work and at the
workplace.
Long term care (Pflegeversicherung) is covered half and half by
employer and employee and covers cases in which a person is not
able to manage his or her daily routine (provision of food,
cleaning of apartment, personal hygiene, etc.). It is about 2% of a
yearly salaried income or pension, with employers matching the
contribution of the employee.
There are two separate systems of health insurance : public health
insurance ( Gesetzliche Krankenversicherung ) and private insurance
( Private Krankenversicherung ). Both systems struggle with the
increasing cost of medical treatment and the changing demography.
About 87.5% of the persons with health insurance are members of the
public system, while 12.5% are covered by private insurance (as of
2006). [ 47 ]
In typical usage, water refers only to its liquid form or state ,
but the substance also has a solid state, ice , and a gaseous
state, water vapor or steam . Water covers 71% of the Earth 's
surface [ 2 ] . On Earth, it is found mostly in oceans and other
large water bodies, with 1.6% of water below ground in aquifers and
0.001% in the air as vapor , clouds (formed of solid and liquid
water particles suspended in air), and precipitation . [ 3 ] Oceans
hold 97% of surface water, glaciers and polar ice caps 2.4%, and
other land surface water such as rivers , lakes and ponds 0.6%. A
very small amount of the Earth's water is contained within
biological bodies and manufactured products.
Water on Earth moves continually through a cycle of evaporation or
transpiration ( evapotranspiration ), precipitation , and runoff ,
usually reaching the sea . Over land, evaporation and transpiration
contribute to the precipitation over land.
Clean, fresh drinking water is essential to human and other
lifeforms. Access to safe drinking water has improved steadily and
substantially over the last decades in almost every part of the
world. [ 4 ] [ 5 ] There is a clear correlation between access to
safe water and GDP per capita. [ 6 ] However, some observers have
estimated that by 2025 more than half of the world population will
be facing water-based vulnerability. [ 7 ] A recent report
(November 2009) suggests that by 2030, in some developing regions
of the world, water demand will exceed supply by 50%. [ 8 ] Water
plays an important role in the world economy , as it functions as a
solvent for a wide variety of chemical substances and facilitates
industrial cooling and transportation. Approximately 70% of
freshwater is consumed by agriculture . [ 9 ]
Contents
1 Chemical and physical properties
2 Taste and odor
3 Distribution of water in nature
3.1 Water in the universe
3.2 Water and habitable zone
4 Water on Earth
4.1 Water cycle
4.2 Fresh water storage
4.3 Sea water
4.4 Tides
5 Effects on life
5.1 Aquatic life forms
6 Effects on human civilization
6.1 Health and pollution
6.2 Human uses
6.2.1 Agriculture
6.2.2 Water as a scientific standard
6.2.3 For drinking
6.2.4 Hygiene
6.2.5 Chemical uses
6.2.6 As a heat transfer fluid
6.2.7 Extinguishing fires
6.2.8 Recreation
6.2.9 Water industry
6.2.10 Industrial applications
6.2.11 Food processing
7 Water law, water politics and water crisis
8 Water in culture
8.1 Religion
8.2 Philosophy
8.3 Literature
9 See also
9.1 Other topics
10 References
11 Further reading
11.1 Water as a natural resource
12 External links
//
Chemical and physical properties
Main articles: Water (properties) , Water (data page) , and Water
model
Model of hydrogen bonds between molecules of water
Impact from a water drop causes an upward "rebound" jet surrounded
by circular capillary waves .
Snowflakes by Wilson Bentley , 1902
Dew drops adhering to a spider web
Capillary action of water compared to mercury
Water is the chemical substance with chemical formula H 2 O : one
molecule of water has two hydrogen atoms covalently bonded to a
single oxygen atom.
Water appears in nature in all three common states of matter and
may take many different forms on Earth: water vapor and clouds in
the sky; seawater and icebergs in the polar oceans; glaciers and
rivers in the mountains ; and the liquid in aquifers in the
ground.
The major chemical and physical properties of water are:
Water is a tasteless, odorless liquid at standard temperature and
pressure . The color of water and ice is, intrinsically, a very
light blue hue, although water appears colorless in small
quantities. Ice also appears colorless, and water vapor is
essentially invisible as a gas. [ 10 ]
Water is transparent , and thus aquatic plants can live within the
water because sunlight can reach them. Only strong UV light is
slightly absorbed .
Since the water molecule is not linear and the oxygen atom has a
higher electronegativity than hydrogen atoms, it carries a slight
negative charge, whereas the hydrogen atoms are slightly positive.
As a result, water is a polar molecule with an electrical dipole
moment . The net interactions between the dipoles on each molecule
cause an effective skin effect at the interface of water with other
substances, or air at the surface, the latter given rise to water's
high surface tension . This dipolar nature contributes to water
molecules' tendency to form hydrogen bonds which cause water's many
special properties. [ 11 ] The polar nature also favors adhesion to
other materials.
Each hydrogen nucleus is bound to the central oxygen atom by a pair
of electrons that are shared between them; chemists call this
shared electron pair a covalent chemical bond. In H 2 O, only two
of the six outer-shell electrons of oxygen are used for this
purpose, leaving four electrons which are organized into two
non-bonding pairs. The four electron pairs surrounding the oxygen
tend to arrange themselves as far from each other as possible in
order to minimize repulsions between these clouds of negative
charge. This would ordinarily result in a tetrahedral geometry in
which the angle between electron pairs (and therefore the H-O-H
bond angle) is 109.5°. However, because the two non-bonding
pairs remain closer to the oxygen atom, these exert a stronger
repulsion against the two covalent bonding pairs, effectively
pushing the two hydrogen atoms closer together. The result is a
distorted tetrahedral arrangement in which the H-O-H angle is
104.5°. [ 12 ]
A result of interplay of these properties, Capillary action refers
to the tendency of water to move up a narrow tube against the force
of gravity . This property is relied upon by all vascular plants ,
such as trees.
Water is a good solvent and is often referred to as the universal
solvent . Substances that dissolve in water, e.g., salts , sugars ,
acids , alkalis , and some gases – especially oxygen, carbon
dioxide ( carbonation ) are known as hydrophilic (water-loving)
substances, while those that do not mix well with water (e.g., fats
and oils ), are known as hydrophobic (water-fearing)
substances.
All the major components in cells ( proteins , DNA and
polysaccharides ) are also dissolved in water.
Pure water has a low electrical conductivity , but this increases
significantly with the dissolution of a small amount of ionic
material such as sodium chloride .
The boiling point of water (and all other liquids) is dependent on
the barometric pressure . For example, on the top of Mt. Everest
water boils at about 68 °C (154 °F), compared to
100 °C (212 °F) at sea level . Conversely, water
deep in the ocean near geothermal vents can reach temperatures of
hundreds of degrees and remain liquid.
Water has the second highest specific heat capacity of any known
substance, after ammonia , as well as a high heat of vaporization
(40.65 kJ·mol −1 ), both of which are a result of
the extensive hydrogen bonding between its molecules. These two
unusual properties allow water to moderate Earth's climate by
buffering large fluctuations in temperature.
The maximum density of water occurs at 3.98 °C
(39.16 °F). [ 13 ] Water becomes even less dense upon
freezing, expanding 9%. This results in an unusual phenomenon:
water's solid form, ice, floats upon water, allowing organisms to
survive inside a partially-frozen water body because the water on
the bottom has a temperature of around 4 °C
(39 °F).
ADR label for transporting goods dangerously reactive with
water
Water is miscible with many liquids, such as ethanol , in all
proportions, forming a single homogeneous liquid. On the other
hand, water and most oils are immiscible usually forming layers
according to increasing density from the top. As a gas, water vapor
is completely miscible with air.
Water forms an azeotrope with many other solvents.
Water can be split by electrolysis into hydrogen and oxygen.
As an oxide of hydrogen, water is formed when hydrogen or
hydrogen-containing compounds burn or react with oxygen or
oxygen-containing compounds. Water is not a fuel , it is an
end-product of the combustion of hydrogen. The energy required to
split water into hydrogen and oxygen by electrolysis or any other
means is greater than the energy released when the hydrogen and
oxygen recombine. [ 14 ]
Elements which are more electropositive than hydrogen such as
lithium , sodium , calcium , potassium and caesium displace
hydrogen from water, forming hydroxides . Being a flammable gas,
the hydrogen given off is dangerous and the reaction of water with
the more electropositive of these elements may be violently
explosive.
Taste and odor
Water can dissolve many different substances, giving it varying
tastes and odors. Humans and other animals have developed senses
which (more or less) enable them to evaluate the potability of
water by avoiding water that is too salty or putrid . Humans also
tend to prefer cold water to lukewarm water since cold water is
likely to contain fewer microbes . The taste advertised in spring
water or mineral water derives from the minerals dissolved in it:
Pure H 2 O is tasteless and odorless. The advertised purity of
spring and mineral water refers to absence of toxins , pollutants
and microbes .
Distribution of water in nature
Water in the universe
Much of the universe's water may be produced as a byproduct of star
formation . When stars are born, their birth is accompanied by a
strong outward wind of gas and dust. When this outflow of material
eventually impacts the surrounding gas, the shock waves that are
created compress and heat the gas. The water observed is quickly
produced in this warm dense gas. [ 15 ]
Water has been detected in interstellar clouds within our galaxy ,
the Milky Way . Water probably exists in abundance in other
galaxies, too, because its components, hydrogen and oxygen, are
among the most abundant elements in the universe. Interstellar
clouds eventually condense into solar nebulae and solar systems
such as ours.
Water vapor is present in:
Atmosphere of Mercury : 3.4%, and large amounts of water in
Mercury's exosphere [ 16 ]
Atmosphere of Venus : 0.002%
Earth's atmosphere : ~0.40% over full atmosphere, typically 1%-4%
at surface
Atmosphere of Mars : 0.03%
Atmosphere of Jupiter : 0.0004%
Atmosphere of Saturn - in ices only
Enceladus (moon of Saturn): 91%
exoplanets known as HD 189733 b [ 17 ] and HD 209458 b . [ 18 ]
Liquid water is present on:
Earth - 71% of surface
Moon - small amounts of water have been found (in 2008) in the
inside of volcanic pearls brought from Moon to Earth by the Apollo
15 crew in 1971. [ 19 ] NASA reported the detection of water
molecules by NASA's Moon Mineralogy Mapper aboard the Indian Space
Research Organization's Chandrayaan-1 spacecraft in September 2009.
[ 20 ]
Strong evidence suggests that liquid water is present just under
the surface of Saturn's moon Enceladus and on Jupiter's moon Europa
where it may exist as a 100 km deep ocean covering the whole
moon which would amount to more water than is in all the Earth's
oceans.
Water ice is present on:
Earth - mainly as ice sheets
polar ice caps on Mars
Moon
Titan
Europa
Saturn's rings [ 21 ]
Enceladus
Pluto and Charon [ 22 ]
Comets and comet source populations ( Kuiper belt and Oort cloud
objects).
Water ice may be present on Ceres and Tethys . Water and other
volatiles probably comprise much of the internal structures of
Uranus and Neptune .
Water and habitable zone
The Solar System along center row range of possible habitable zones
of varying size stars.
The existence of liquid water, and to a lesser extent its gaseous
and solid forms, on Earth are vital to the existence of life on
Earth as we know it. The Earth is located in the habitable zone of
the solar system ; if it were slightly closer to or further from
the Sun (about 5%, or about 8 million kilometers), the conditions
which allow the three forms to be present simultaneously would be
far less likely to exist. [ 23 ] [ 24 ]
Earth's gravity allows it to hold an atmosphere . Water vapor and
carbon dioxide in the atmosphere provide a temperature buffer (
greenhouse effect ) which helps maintain a relatively steady
surface temperature. If Earth were smaller, a thinner atmosphere
would allow temperature extremes, thus preventing the accumulation
of water except in polar ice caps (as on Mars ).
The surface temperature of Earth has been relatively constant
through geologic time despite varying levels of incoming solar
radiation ( insolation ), indicating that a dynamic process governs
Earth's temperature via a combination of greenhouse gases and
surface or atmospheric albedo . This proposal is known as the Gaia
hypothesis .
The state of water on a planet depends on ambient pressure, which
is determined by the planet's gravity. If a planet is sufficiently
massive, the water on it may be solid even at high temperatures,
because of the high pressure caused by gravity.
There are various theories about origin of water on Earth .
Water on Earth
Main articles: Hydrology and Water distribution on Earth
A graphical distribution of the locations of water on Earth.
Water covers 71% of the Earth's surface; the oceans contain 97.2%
of the Earth's water. The Antarctic ice sheet , which contains 90%
of all fresh water on Earth, is visible at the bottom. Condensed
atmospheric water can be seen as clouds , contributing to the
Earth's albedo .
Hydrology is the study of the movement, distribution, and quality
of water throughout the Earth. The study of the distribution of
water is hydrography . The study of the distribution and movement
of groundwater is hydrogeology , of glaciers is glaciology , of
inland waters is limnology and distribution of oceans is
oceanography . Ecological processes with hydrology are in focus of
ecohydrology .
The collective mass of water found on, under, and over the surface
of a planet is called the hydrosphere . Earth's approximate water
volume (the total water supply of the world) is
1,360,000,000 km 3 (326,000,000 mi 3 ).
Groundwater and fresh water are useful or potentially useful to
humans as water resources .
Liquid water is found in bodies of water , such as an ocean, sea ,
lake , river , stream , canal , pond , or puddle . The majority of
water on Earth is sea water . Water is also present in the
atmosphere in solid, liquid, and vapor states. It also exists as
groundwater in aquifers .
Water is important in many geological processes. Groundwater is
ubiquitous in rocks , and the pressure of this groundwater affects
patterns of faulting . Water in the mantle is responsible for the
melt that produces volcanoes at subduction zones . On the surface
of the Earth, water is important in both chemical and physical
weathering processes. Water and, to a lesser but still significant
extent, ice, are also responsible for a large amount of sediment
transport that occurs on the surface of the earth. Deposition of
transported sediment forms many types of sedimentary rocks , which
make up the geologic record of Earth history .
Water cycle
Main article: Water cycle
Water cycle
The water cycle (known scientifically as the hydrologic cycle )
refers to the continuous exchange of water within the hydrosphere ,
between the atmosphere , soil water, surface water , groundwater ,
and plants .
Water moves perpetually through each of these regions in the water
cycle consisting of following transfer processes:
evaporation from oceans and other water bodies into the air and
transpiration from land plants and animals into air.
precipitation , from water vapor condensing from the air and
falling to earth or ocean.
runoff from the land usually reaching the sea .
Most water vapor over the oceans returns to the oceans, but winds
carry water vapor over land at the same rate as runoff into the
sea, about 36 Tt per year. Over land, evaporation and
transpiration contribute another 71 Tt per year.
Precipitation, at a rate of 107 Tt per year over land, has several
forms: most commonly rain , snow , and hail , with some
contribution from fog and dew . Condensed water in the air may also
refract sunlight to produce rainbows .
Water runoff often collects over watersheds flowing into rivers. A
mathematical model used to simulate river or stream flow and
calculate water quality parameters is hydrological transport model
. Some of water is diverted to irrigation for agriculture. Rivers
and seas offer opportunity for travel and commerce . Through
erosion , runoff shapes the environment creating river valleys and
deltas which provide rich soil and level ground for the
establishment of population centers. A flood occurs when an area of
land, usually low-lying, is covered with water. It is when a river
overflows its banks or flood from the sea. A drought is an extended
period of months or years when a region notes a deficiency in its
water supply. This occurs when a region receives consistently below
average precipitation.
Fresh water storage
High tide (left) and low tide (right)
Main article: Water resources
Some runoff water is trapped for periods of time, for example in
lakes. At high altitude, during winter, and in the far north and
south, snow collects in ice caps, snow pack and glaciers. Water
also infiltrates the ground and goes into aquifers. This
groundwater later flows back to the surface in springs , or more
spectacularly in hot springs and geysers . Groundwater is also
extracted artificially in wells . This water storage is important,
since clean, fresh water is essential to human and other land-based
life. In many parts of the world, it is in short supply.
Sea water
Main article: Seawater
Sea water contains about 3.5% salt on average, plus smaller amounts
of other substances. The physical properties of sea water differ
from fresh water in some important respects. It freezes at a lower
temperature (about -1.9C) and its density increases with decreasing
temperature to the freezing point, instead of reaching maximum
density at a temperature above freezing. The salinity of water in
major seas varies from about 0.7% in the Baltic Sea to 4.0% in the
Red Sea .
Tides
Main article: Tide
Tides are the cyclic rising and falling of Earth's ocean surface
caused by the tidal forces of the Moon and the Sun acting on the
oceans. Tides cause changes in the depth of the marine and
estuarine water bodies and produce oscillating currents known as
tidal streams. The changing tide produced at a given location is
the result of the changing positions of the Moon and Sun relative
to the Earth coupled with the effects of Earth rotation and the
local bathymetry . The strip of seashore that is submerged at high
tide and exposed at low tide, the intertidal zone , is an important
ecological product of ocean tides.
Effects on life
An oasis is an isolated water source with vegetation in desert
Overview of photosynthesis and respiration . Water (at right),
together with carbon dioxide (CO 2 ), form oxygen and organic
compounds (at left), which can be respired to water and (CO 2
).
From a biological standpoint, water has many distinct properties
that are critical for the proliferation of life that set it apart
from other substances. It carries out this role by allowing organic
compounds to react in ways that ultimately allow replication . All
known forms of life depend on water. Water is vital both as a
solvent in which many of the body's solutes dissolve and as an
essential part of many metabolic processes within the body.
Metabolism is the sum total of anabolism and catabolism. In
anabolism, water is removed from molecules (through energy
requiring enzymatic chemical reactions) in order to grow larger
molecules (e.g. starches, triglycerides and proteins for storage of
fuels and information). In catabolism, water is used to break bonds
in order to generate smaller molecules (e.g. glucose, fatty acids
and amino acids to be used for fuels for energy use or other
purposes). Water is thus essential and central to these metabolic
processes. Therefore, without water, these metabolic processes
would cease to exist, leaving us to muse about what processes would
be in its place, such as gas absorption, dust collection, etc.
Water is also central to photosynthesis and respiration.
Photosynthetic cells use the sun's energy to split off water's
hydrogen from oxygen. Hydrogen is combined with CO 2 (absorbed from
air or water) to form glucose and release oxygen. All living cells
use such fuels and oxidize the hydrogen and carbon to capture the
sun's energy and reform water and CO 2 in the process (cellular
respiration).
Water is also central to acid-base neutrality and enzyme function.
An acid, a hydrogen ion (H + , that is, a proton) donor, can be
neutralized by a base, a proton acceptor such as hydroxide ion (OH
− ) to form water. Water is considered to be neutral, with a
pH (the negative log of the hydrogen ion concentration) of 7. Acids
have pH values less than 7 while bases have values greater than
7.
Some of the biodiversity of a coral reef
Stomach acid (HCl) is useful to digestion. However, its corrosive
effect on the esophagus during reflux can temporarily be
neutralized by ingestion of a base such as aluminum hydroxide to
produce the neutral molecules water and the salt aluminum chloride.
Human biochemistry that involves enzymes usually performs optimally
around a biologically neutral pH of 7.4.
For example, a cell of Escherichia coli contains 70% of water, a
human body 60–70%, plant body up to 90% and the body of an
adult jellyfish is made up of 94–98% water.
Aquatic life forms
Main articles: Hydrobiology and Aquatic plant
Some marine diatoms - a key phytoplankton group
Earth's waters are filled with life. The earliest life forms
appeared in water; nearly all fish live exclusively in water, and
there are many types of marine mammals, such as dolphins and whales
that also live in the water. Some kinds of animals, such as
amphibians , spend portions of their lives in water and portions on
land. Plants such as kelp and algae grow in the water and are the
basis for some underwater ecosystems. Plankton is generally the
foundation of the ocean food chain .
Aquatic animals must obtain oxygen to survive, and they do so in
various ways. Fish have gills instead of lungs , although some
species of fish, such as the lungfish , have both. Marine mammals ,
such as dolphins, whales, otters , and seals need to surface
periodically to breathe air. Smaller life forms are able to absorb
oxygen through their skin.
Effects on human civilization
Water fountain
Civilization has historically flourished around rivers and major
waterways; Mesopotamia , the so-called cradle of civilization, was
situated between the major rivers Tigris and Euphrates ; the
ancient society of the Egyptians depended entirely upon the Nile .
Large metropolises like Rotterdam , London , Montreal , Paris , New
York City , Buenos Aires , Shanghai , Tokyo , Chicago , and Hong
Kong owe their success in part to their easy accessibility via
water and the resultant expansion of trade. Islands with safe water
ports, like Singapore , have flourished for the same reason. In
places such as North Africa and the Middle East , where water is
more scarce, access to clean drinking water was and is a major
factor in human development.
Health and pollution
Environmental Science Program, Iowa State University student
sampling water.
Water fit for human consumption is called drinking water or potable
water . Water that is not potable can be made potable by filtration
or distillation (heating it until it becomes water vapor, and then
capturing the vapor without any of the impurities it leaves
behind), or by other methods (chemical or heat treatment that kills
bacteria). Sometimes the term safe water is applied to potable
water of a lower quality threshold (i.e., it is used effectively
for nutrition in humans that have weak access to water cleaning
processes, and does more good than harm). Water that is not fit for
drinking but is not harmful for humans when used for swimming or
bathing is called by various names other than potable or drinking
water, and is sometimes called safe water , or "safe for bathing".
Chlorine is a skin and mucous membrane irritant that is used to
make water safe for bathing or drinking. Its use is highly
technical and is usually monitored by government regulations
(typically 1 part per million (ppm) for drinking water, and
1–2 ppm of chlorine not yet reacted with impurities for
bathing water).
This natural resource is becoming scarcer in certain places, and
its availability is a major social and economic concern. Currently,
about a billion people around the world routinely drink unhealthy
water. Most countries accepted the goal of halving by 2015 the
number of people worldwide who do not have access to safe water and
sanitation during the 2003 G8 Evian summit . [ 25 ] Even if this
difficult goal is met, it will still leave more than an estimated
half a billion people without access to safe drinking water and
over a billion without access to adequate sanitation. Poor water
quality and bad sanitation are deadly; some five million deaths a
year are caused by polluted drinking water. The World Health
Organization estimates that safe water could prevent 1.4 million
child deaths from diarrhea each year. [ 26 ] Water, however, is not
a finite resource, but rather re-circulated as potable water in
precipitation in quantities many degrees of magnitude higher than
human consumption. Therefore, it is the relatively small quantity
of water in reserve in the earth (about 1% of our drinking water
supply , which is replenished in aquifers around every 1 to 10
years), that is a non-renewable resource, and it is, rather, the
distribution of potable and irrigation water which is scarce,
rather than the actual amount of it that exists on the earth.
Water-poor countries use importation of goods as the primary method
of importing water (to leave enough for local human consumption),
since the manufacturing process uses around 10 to 100 times
products' masses in water.
In the developing world, 90% of all wastewater still goes untreated
into local rivers and streams. [ 27 ] Some 50 countries, with
roughly a third of the world’s population, also suffer from
medium or high water stress, and 17 of these extract more water
annually than is recharged through their natural water cycles. [ 28
] The strain not only affects surface freshwater bodies like rivers
and lakes, but it also degrades groundwater resources.
Human uses
Agriculture
Irrigation of field crops
The most important use of water in agriculture is for irrigation ,
which is a key component to produce enough food. Irrigation takes
up to 90% of water withdrawn in some developing countries [ 29 ]
and significant proportions in more economically developed
countries (United States, 30% of freshwater usage is for
irrigation). [ 30 ]
Water as a scientific standard
On 7 April 1795, the gram was defined in France to be equal to "the
absolute weight of a volume of pure water equal to a cube of one
hundredth of a meter, and to the temperature of the melting ice." [
31 ] For practical purposes though, a metallic reference standard
was required, one thousand times more massive, the kilogram . Work
was therefore commissioned to determine precisely the mass of one
liter of water. In spite of the fact that the decreed definition of
the gram specified water at 0 °C—a highly
reproducible temperature —the scientists chose to redefine
the standard and to perform their measurements at the temperature
of highest water density , which was measured at the time as
4 °C (39 °F). [ 32 ]
The Kelvin temperature scale of the SI system is based on the
triple point of water, defined as exactly 273.16 K or
0.01 °C. The scale is a more accurate development of the
Celsius temperature scale, which was originally defined according
the boiling point (set to 100 °C) and melting point (set
to 0 °C) of water.
Natural water consists mainly of the isotopes hydrogen-1 and
oxygen-16, but there is also small quantity of heavier isotopes
such as hydrogen-2 ( deuterium ). The amount of deuterium oxides or
heavy water is very small, but it still affects the properties of
water. Water from rivers and lakes tends to contain less deuterium
than seawater. Therefore, standard water is defined in the Vienna
Standard Mean Ocean Water specification.
For drinking
Main article: Drinking water
A young girl drinking bottled water
Water quality: fraction of population using improved water sources
by country
The human body is anywhere from 55% to 78% water depending on body
size. [ 33 ] To function properly, the body requires between one
and seven liters of water per day to avoid dehydration ; the
precise amount depends on the level of activity, temperature,
humidity, and other factors. Most of this is ingested through foods
or beverages other than drinking straight water. It is not clear
how much water intake is needed by healthy people, though most
advocates agree that 6–7 glasses of water (approximately 2
liters) daily is the minimum to maintain proper hydration. [ 34 ]
Medical literature favors a lower consumption, typically 1 liter of
water for an average male, excluding extra requirements due to
fluid loss from exercise or warm weather. [ 35 ] For those who have
healthy kidneys, it is rather difficult to drink too much water,
but (especially in warm humid weather and while exercising) it is
dangerous to drink too little. People can drink far more water than
necessary while exercising, however, putting them at risk of water
intoxication (hyperhydration), which can be fatal. The "fact" that
a person should consume eight glasses of water per day cannot be
traced back to a scientific source. [ 36 ] There are other myths
such as the effect of water on weight loss and constipation that
have been dispelled. [ 37 ]
Hazard symbol for No drinking water
An original recommendation for water intake in 1945 by the Food and
Nutrition Board of the National Research Council read: "An ordinary
standard for diverse persons is 1 milliliter for each calorie of
food. Most of this quantity is contained in prepared foods." [ 38 ]
The latest dietary reference intake report by the United States
National Research Council in general recommended (including food
sources): 2.7 liters of water total for women and 3.7 liters for
men. [ 39 ] Specifically, pregnant and breastfeeding women need
additional fluids to stay hydrated. According to the Institute of
Medicine —who recommend that, on average, women consume 2.2
liters and men 3.0 liters—this is recommended to be 2.4
liters (10 cups) for pregnant women and 3 liters (12 cups) for
breastfeeding women since an especially large amount of fluid is
lost during nursing. [ 40 ] Also noted is that normally, about 20%
of water intake comes from food, while the rest comes from drinking
water and beverages ( caffeinated included). Water is excreted from
the body in multiple forms; through urine and faeces , through
sweating , and by exhalation of water vapor in the breath. With
physical exertion and heat exposure, water loss will increase and
daily fluid needs may increase as well.
Humans require water that does not contain too many impurities.
Common impurities include metal salts and oxides (including copper,
iron, calcium and lead) [ 41 ] and/or harmful bacteria , such as
Vibrio . Some solutes are acceptable and even desirable for taste
enhancement and to provide needed electrolytes . [ 42 ]
The single largest freshwater resource suitable for drinking is
Lake Baikal in Siberia, which has a very low salt and calcium
content and is therefore very clean.
Hygiene
The ability of water to make solutions and emulsions is used for
washing. Many industrial processes rely on reactions using
chemicals dissolved in water, suspension of solids in water
slurries or using water to dissolve and extract substances.
Chemical uses
Water is widely used in chemical reactions as a solvent or reactant
and less commonly as a solute or catalyst. In inorganic reactions,
water is a common solvent, dissolving many ionic compounds. In
organic reactions, it is not usually used as a reaction solvent,
because it does not dissolve the reactants well and is amphoteric
(acidic and basic) and nucleophilic . Nevertheless, these
properties are sometimes desirable. Also, acceleration of
Diels-Alder reactions by water has been observed. Supercritical
water has recently been a topic of research. Oxygen-saturated
supercritical water combusts organic pollutants efficiently.
As a heat transfer fluid
Ice used for cooling.
Water and steam are used as heat transfer fluids in diverse heat
exchange systems, due to its availability and high heat capacity,
both as a coolant and for heating. Cool water may even be naturally
available from a lake or the sea. Condensing steam is a
particularly efficient heating fluid because of the large heat of
vaporization. A disadvantage is that water and steam are somewhat
corrosive. In almost all electric power stations , water is the
coolant, which vaporizes and drives steam turbines to drive
generators. In the U.S., cooling power plants is the largest use of
water. [ 30 ]
In the nuclear industry, water can also be used as a neutron
moderator . In a pressurized water reactor , water is both a
coolant and a moderator. This provides a passive safety measure, as
removing the water from the reactor also slows the nuclear reaction
down.
Extinguishing fires
Water is used for fighting wildfires .
Water has a high heat of vaporization and is relatively inert,
which makes it a good fire extinguishing fluid. The evaporation of
water carries heat away from the fire. However, water cannot be
used to fight fires of electric equipment, because impure water is
electrically conductive, or of oils and organic solvents, because
they float on water and the explosive boiling of water tends to
spread the burning liquid.
Use of water in fire fighting should also take into account the
hazards of a steam explosion , which may occur when water is used
on very hot fires in confined spaces, and of a hydrogen explosion,
when substances which react with water, such as certain metals or
hot graphite, decompose the water, producing hydrogen gas .
The power of such explosions was seen in the Chernobyl disaster ,
although the water involved did not come from fire-fighting at that
time but the reactor's own water cooling system. A steam explosion
occurred when the extreme over-heating of the core caused water to
flash into steam. A hydrogen explosion may have occurred as a
result of reaction between steam and hot zirconium .
Recreation
Main article: Water sport (recreation)
Humans use water for many recreational purposes, as well as for
exercising and for sports. Some of these include swimming ,
waterskiing , boating , surfing and diving . In addition, some
sports, like ice hockey and ice skating , are played on ice.
Lakesides, beaches and waterparks are popular places for people to
go to relax and enjoy recreation. Many find the sound and
appearance of flowing water to be calming, and fountains and other
water features in public or private decorations.. Some keep fish
and other life in aquariums or ponds for show, fun, and
companionship. Humans also use water for snow sports i.e. skiing ,
sledding , snowmobiling or snowboarding , which requires the water
to be frozen. People may also use water for play fighting such as
with snowballs , water guns or water balloons .
Water industry
A water-carrier in India , 1882. In many places where running water
was not available, water had to be transported by people.
A manual water pump in China
Water purification facility
Main articles: Water industry and :Category:Water supply and
sanitation by country
The water industry provides drinking water and wastewater services
(including sewage treatment ) to households and industry . Water
supply facilities include water wells cisterns for rainwater
harvesting , water supply network , water purification facilities,
water tanks , water towers , water pipes including old aqueducts .
Atmospheric water generators are in development.
Drinking water is often collected at springs , extracted from
artificial borings (wells) in the ground, or pumped from lakes and
rivers. Building more wells in adequate places is thus a possible
way to produce more water, assuming the aquifers can supply an
adequate flow. Other water sources include rainwater collection.
Water may require purification for human consumption. This may
involve removal of undissolved substances, dissolved substances and
harmful microbes . Popular methods are filtering with sand which
only removes undissolved material, while chlorination and boiling
kill harmful microbes. Distillation does all three functions. More
advanced techniques exist, such as reverse osmosis . Desalination
of abundant seawater is a more expensive solution used in coastal
arid climates .
The distribution of drinking water is done through municipal water
systems , tanker delivery or as bottled water . Governments in many
countries have programs to distribute water to the needy at no
charge. Others argue that the market mechanism and free enterprise
are best to manage this rare resource and to finance the boring of
wells or the construction of dams and reservoirs .
Reducing usage by using drinking (potable) water only for human
consumption is another option. In some cities such as Hong Kong ,
sea water is extensively used for flushing toilets citywide in
order to conserve fresh water resources .
Polluting water may be the biggest single misuse of water; to the
extent that a pollutant limits other uses of the water, it becomes
a waste of the resource, regardless of benefits to the polluter.
Like other types of pollution, this does not enter standard
accounting of market costs, being conceived as externalities for
which the market cannot account. Thus other people pay the price of
water pollution, while the private firms' profits are not
redistributed to the local population victim of this pollution.
Pharmaceuticals consumed by humans often end up in the waterways
and can have detrimental effects on aquatic life if they
bioaccumulate and if they are not biodegradable .
Wastewater facilities are storm sewers and wastewater treatment
plants . Another way to remove pollution from surface runoff water
is bioswale .
Industrial applications
Water is used in power generation . Hydroelectricity is electricity
obtained from hydropower . Hydroelectric power comes from water
driving a water turbine connected to a generator. Hydroelectricity
is a low-cost, non-polluting, renewable energy source. The energy
is supplied by the sun. Heat from the sun evaporates water, which
condenses as rain in higher altitudes, from where it flows
down.
Three Gorges Dam is the largest hydro-electric power station .
Pressurized water is used in water blasting and water jet cutters .
Also, very high pressure water guns are used for precise cutting.
It works very well, is relatively safe, and is not harmful to the
environment. It is also used in the cooling of machinery to prevent
over-heating, or prevent saw blades from over-heating.
Water is also used in many industrial processes and machines, such
as the steam turbine and heat exchanger , in addition to its use as
a chemical solvent . Discharge of untreated water from industrial
uses is pollution . Pollution includes discharged solutes (
chemical pollution ) and discharged coolant water (thermal
pollution). Industry requires pure water for many applications and
utilizes a variety of purification techniques both in water supply
and discharge.
Food processing
Water can be used to cook foods such as noodles .
Water plays many critical roles within the field of food science .
It is important for a food scientist to understand the roles that
water plays within food processing to ensure the success of their
products.
Solutes such as salts and sugars found in water affect the physical
properties of water. The boiling and freezing points of water is
affected by solutes. One mole of sucrose (sugar) per kilogram of
water raises the boiling point of water by 0.51 °C, and one
mole of salt per kg raises the boiling point by 1.02 °C;
similarly, increasing the number of dissolved particles lowers
water's freezing point. [ 43 ] Solutes in water also affect water
activity which affects many chemical reactions and the growth of
microbes in food. [ 44 ] Water activity can be described as a ratio
of the vapor pressure of water in a solution to the vapor pressure
of pure water. [ 43 ] Solutes in water lower water activity. This
is important to know because most bacterial growth ceases at low
levels of water activity. [ 44 ] Not only does microbial growth
affect the safety of food but also the preservation and shelf life
of food.
Water hardness is also a critical factor in food processing. It can
dramatically affect the quality of a product as well as playing a
role in sanitation. Water hardness is classified based on the
amounts of removable calcium carbonate salt it contains per gallon.
Water hardness is measured in grains; 0.064 g calcium carbonate is
equivalent to one grain of hardness. [ 43 ] Water is classified as
soft if it contains 1 to 4 grains, medium if it contains 5 to 10
grains and hard if it contains 11 to 20 grains. [ vague ] [ 43 ]
The hardness of water may be altered or treated by using a chemical
ion exchange system. The hardness of water also affects its pH
balance which plays a critical role in food processing. For
example, hard water prevents successful production of clear
beverages. Water hardness also affects sanitation; with increasing
hardness, there is a loss of effectiveness for its use as a
sanitizer. [ 43 ]
Boiling , steaming , and simmering are popular cooking methods that
often require immersing food in water or its gaseous state, steam.
Water is also used for dishwashing .
Water law, water politics and water crisis
Best estimate of the share of people in developing countries with
access to drinking water 1970–2000
Main articles: Water law , Water right , Water politics , and Water
crisis
See also: Water resources
Water politics is politics affected by water and water resources .
For this reason, water is a strategic resource in the globe and an
important element in many political conflicts. It causes health
impacts and damage to biodiversity.
1.6 billion people have gained access to a safe water source since
1990 [1] . The proportion of people in developing countries with
access to safe water is calculated to have improved from 30% in
1970 [ 4 ] to 71% in 1990, 79% in 2000 and 84% in 2004. This trend
is projected to continue. [ 5 ] To halve, by 2015, the proportion
of people without sustainable access to safe drinking water is one
of the Millennium Development Goals . This goal is projected to be
reached.
A 2006 United Nations report stated that "there is enough water for
everyone", but that access to it is hampered by mismanagement and
corruption. [ 45 ]
The UN World Water Development Report (WWDR, 2003) from the World
Water Assessment Program indicates that, in the next 20 years, the
quantity of water available to everyone is predicted to decrease by
30%. 40% of the world's inhabitants currently have insufficient
fresh water for minimal hygiene . More than 2.2 million people died
in 2000 from waterborne diseases (related to the consumption of
contaminated water) or drought . In 2004, the UK charity WaterAid
reported that a child dies every 15 seconds from easily preventable
water-related diseases; often this means lack of sewage disposal;
see toilet .
Organizations concerned with water protection include International
Water Association (IWA), WaterAid , Water 1st , American Water
Resources Association . Water related conventions are United
Nations Convention to Combat Desertification (UNCCD), International
Convention for the Prevention of Pollution from Ships , United
Nations Convention on the Law of the Sea and Ramsar Convention .
World Day for Water takes place on 22 March and World Ocean Day on
8 June.
Water used in the production of a good or service is virtual water
.
Water in culture
Religion
Main article: Water and religion
Water is considered a purifier in most religions. Major faiths that
incorporate ritual washing ( ablution ) include Christianity ,
Hinduism , Rastafari movement , Islam , Shinto , Taoism , and
Judaism . Immersion (or aspersion or affusion ) of a person in
water is a central sacrament of Christianity (where it is called
baptism ); it is also a part of the practice of other religions,
including Judaism ( mikvah ) and Sikhism ( Amrit Sanskar ). In
addition, a ritual bath in pure water is performed for the dead in
many religions including Judaism and Islam. In Islam, the five
daily prayers can be done in most cases (see Tayammum ) after
completing washing certain parts of the body using clean water (
wudu ). In Shinto, water is used in almost all rituals to cleanse a
person or an area (e.g., in the ritual of misogi ). Water is
mentioned in the Bible 442 times in the New International Version
and 363 times in the King James Version : 2 Peter 3:5(b) states,
"The earth was formed out of water and by water" (NIV). In the
Koran it is stated that "Living things are made of water" and it is
often used to described Paradise.
Philosophy
The Ancient Greek philosopher Empedocles held that water is one of
the four classical elements along with fire , earth and air , and
was regarded as the ylem , or basic substance of the universe.
Water was considered cold and moist. In the theory of the four
bodily humors , water was associated with phlegm . The classical
element of Water was also one of the five elements in traditional
Chinese philosophy , along with earth , fire , wood , and metal
.
Water is also taken as a role model in some parts of traditional
and popular Asian philosophy. James Legge's 1891 translation of the
Dao De Jing states "The highest excellence is like (that of) water.
The excellence of water appears in its benefiting all things, and
in its occupying, without striving (to the contrary), the low place
which all men dislike. Hence (its way) is near to (that of) the
Tao" and "There is nothing in the world more soft and weak than
water, and yet for attacking things that are firm and strong there
is nothing that can take precedence of it—for there is
nothing (so effectual) for which it can be changed." [ 46 ]
Literature
Water is used in literature as a symbol of purification. Examples
include the critical importance of a river in As I Lay Dying by
William Faulkner and the drowning of Ophelia in Hamlet .
Sherlock Holmes held that "From a drop of water, a logician could
infer the possibility of an Atlantic or a Niagara without having
seen or heard of one or the other." [ 47 ]
In chemistry , an alkali (from Arabic : Al-Qaly
القلي,
القالي ) is a basic , ionic
salt of an alkali metal or alkaline earth metal element . Alkalis
are best known for being bases that dissolve in water . Bases are
compounds with a pH greater than 7. The adjective alkaline is
commonly used in English as a synonym for base, especially for
soluble bases. This broad use of the term is likely to have come
about because alkalis were the first bases known to obey the
Arrhenius definition of a base and are still among the more common
bases. Since Brønsted-Lowry acid-base theory , the term
alkali in chemistry is normally restricted to those salts
containing alkali and alkaline earth metal elements.
Contents
1 Etymology
2 Common properties
3 Confusion between alkali and base
4 Salts
5 Alkaline soil
6 Lakes
7 References
//
Etymology
The word "alkali" is derived from Arabic al qalīy = the
calcined ashes , referring to the original source of alkaline
substance. Ashes were used in conjunction with animal fat to
produce soap , a process known as saponification .
Common properties
Alkalis are all Arrhenius bases, which form hydroxide ions (OH - )
when dissolved in water. Common properties of alkaline aqueous
solutions include:
Moderately-concentrated solutions (over 10 −3 M) have a pH of
7.1 or greater. This means that they will turn phenolphthalein from
colorless to pink.
Concentrated solutions are caustic (causing chemical burns).
Alkaline solutions are slippery or soapy to the touch, due to the
saponification of the fatty acids on the surface of the skin.
Alkalis are normally water soluble , although some like barium
carbonate are only soluble when reacting with an acidic aqueous
solution.
Acids and alkalis are measured on a pH scale
Alkalis are commonly found in household cleaners and toothpaste
Confusion between alkali and base
The terms "base" and "alkali" are often used interchangeably,
particularly outside of a scientific context, but they do not have
the same meaning. While all alkaline solutions are basic, not all
bases are alkaline. The following are common mistakes:
The phrase "measuring the alkalinity of soil" is incorrect since
the property measured is actually the pH (base property).
Calling bases that are not alkalis, such as ammonia , alkaline
(ammonia is a base but not an alkali).
Also, not all salts formed by alkali metals are alkaline; this
designation applies only to those salts that are basic. And while
most electropositive metal oxides are basic, only the soluble
alkali metal and alkaline earth metal oxides can be correctly
called alkalis.
This definition of an alkali as a basic salt of an alkali metal or
alkaline earth metal is the most common, based on dictionary
definitions [1] [2] , however conflicting definitions of the term
alkali do exist. These include:
Any base that is water-soluble and forms hydroxide ions [3] [4] .
In chemistry, this is more accurately called an Arrhenius base
.
The solution of a base in water [5] . This would be an Arrhenius
base in solution.
Name given by chemists to an important group of subtances, the
behaviour of bases the main alkali are 1,the hydroxides potassium
2,
Salts
Most basic salts are alkali salts, of which common examples
are:
sodium hydroxide (often called "caustic soda")
potassium hydroxide (commonly called "caustic potash")
lye (generic term, for either of the previous two, or even for a
mixture)
calcium carbonate (sometimes called "free lime")
magnesium hydroxide is an example of an atypical alkali since it
has low solubility in water (although the dissolved portion is
considered a strong base due to complete dissociation of its
ions).
Alkaline soil
Soil with a pH value higher than 7.3 is normally referred to as
alkaline. This soil property can occur naturally, due to the
presence of alkali salts. Although some plants do prefer slightly
basic soil (including vegetables like cabbage and fodder like
buffalograss ), most plants prefer a mildly acidic soil (pH between
6.0 and 6.8), and alkaline soils can cause problems.
Lakes
In alkali lakes (a type of salt lake ), evaporation concentrates
the naturally-occurring alkali salts, often forming a crust of
mildly-basic salt across a large area.
Examples of alkali lakes:
Redberry Lake, Saskatchewan , Canada .
Tramping Lake, Saskatchewan , Canada.
Mono lake , California , United States
Summer Lake , Oregon , United States
Alkali Lake, British Columbia and the adjoining reserves of the
Alkali Lake Indian Band are named for a local Alkali Lake, which
got its name from a large patch of alkali on the hillside above the
lake, which is not itself alkali, [ 1 ] although there are many in
the Cariboo district and adjoining regions of the British Columbia
Interior .
In chemistry , an electrolyte is any substance containing free ions
that make the substance electrically conductive . The most typical
electrolyte is an ionic solution , but molten electrolytes and
solid electrolytes are also possible.
Electrolytes commonly exist as solutions of acids, bases or salts.
Furthermore, some gases may act as electrolytes under conditions of
high temperature or low pressure. Electrolyte solutions can also
result from the dissolution of some biological (e.g., DNA,
polypeptides) and synthetic polymers (e.g., polystyrene sulfonate),
termed polyelectrolytes, which contain charged functional
group.
Electrolyte solutions are normally formed when a salt is placed
into a solvent such as water and the individual components
dissociate due to the thermodynamic interactions between solvent
and solute molecules, in a process called solvation. For example,
when table salt, NaCl, is placed in water, the salt (a solid)
dissolves into its component elements, according to the
dissociation reaction
NaCl (s) → Na + (aq) + Cl − (aq)
It is also possible for substances to react with water when they
are added to it, producing ions, e.g., carbon dioxide gas dissolves
in water to produce a solution which contains hydronium, carbonate,
and hydrogen carbonate ions.
Note that molten salts can be electrolytes as well. For instance,
when sodium chloride is molten, the liquid conducts
electricity.
An electrolyte in a solution may be described as concentrated if it
has a high concentration of ions, or dilute if it has a low
concentration. If a high proportion of the solute dissociates to
form free ions, the electrolyte is strong; if most of the solute
does not dissociate, the electrolyte is weak. The properties of
electrolytes may be exploited using electrolysis to extract
constituent elements and compounds contained within the
solution.
Contents
1 Physiological importance
1.1 Measurement
1.2 Sports drinks
2 Electrochemistry
3 Dry electrolyte
4 See also
5 References
//
Physiological importance
In physiology , the primary ions of electrolytes are sodium (Na +
), potassium (K + ), calcium (Ca 2+ ), magnesium (Mg 2+ ), chloride
(Cl − ), hydrogen phosphate (HPO 4 2− ), and hydrogen
carbonate (HCO 3 − ). The electric charge symbols of plus (+)
and minus (−) indicate that the substance in question is
ionic in nature and has an imbalanced distribution of electrons,
which is the result of chemical dissociation.
All known higher lifeforms require a subtle and complex electrolyte
balance between the intracellular and extracellular milieu. In
particular, the maintenance of precise osmotic gradients of
electrolytes is important. Such gradients affect and regulate the
hydration of the body, blood pH , and are critical for nerve and
muscle function. Various mechanisms exist in living species that
keep the concentrations of different electrolytes under tight
control.
Both muscle tissue and neurons are considered electric tissues of
the body. Muscles and neurons are activated by electrolyte activity
between the extracellular fluid or interstitial fluid , and
intracellular fluid . Electrolytes may enter or leave the cell
membrane through specialized protein structures embedded in the
plasma membrane called ion channels . For example, muscle
contraction is dependent upon the presence of calcium (Ca 2+ ),
sodium (Na + ), and potassium (K + ). Without sufficient levels of
these key electrolytes, muscle weakness or severe muscle
contractions may occur.
Electrolyte balance is maintained by oral, or in emergencies,
intravenous (IV) intake of electrolyte-containing substances, and
is regulated by hormones , generally with the kidneys flushing out
excess levels. In humans, electrolyte homeostasis is regulated by
hormones such as antidiuretic hormone , aldosterone and parathyroid
hormone . Serious electrolyte disturbances , such as dehydration
and overhydration , may lead to cardiac and neurological
complications and, unless they are rapidly resolved, will result in
a medical emergency .
Measurement
Measurement of electrolytes is a commonly performed diagnostic
procedure, performed via blood testing with ion selective
electrodes or urinalysis by medical technologists . The
interpretation of these values is somewhat meaningless without
analysis of the clinical history and is often impossible without
parallel measurement of renal function . Electrolytes measured most
often are sodium and potassium. Chloride levels are rarely measured
except for arterial blood gas interpretation since they are
inherently linked to sodium levels. One important test conducted on
urine is the specific gravity test to determine the occurrence of
electrolyte imbalance .
Sports drinks
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Electrolytes are commonly found in sports drinks . In oral
rehydration therapy , electrolyte drinks containing sodium and
potassium salts replenish the body's water and electrolyte levels
after dehydration caused by exercise , diaphoresis , diarrhea ,
vomiting , intoxication or starvation . Athletes exercising in
extreme conditions (for three or more hours continuously e.g.
marathon or triathlon) who do not consume electrolytes risk
dehydration (or hyponatremia ) [ 1 ] .
A simple electrolyte drink can be home-made by using the correct
proportions of water, sugar, salt, salt substitute for potassium,
and baking soda. [ 2 ] However, effective electrolyte replacements
should include all electrolytes required by the body, including
sodium chloride, potassium, magnesium, and calcium that can be
either obtained in a sports drink or a solid electrolyte capsule. [
3 ]
Electrochemistry
Main article: electrolysis
When electrodes are placed in an electrolyte and a voltage is
applied, the electrolyte will conduct electricity. Lone electrons
normally cannot pass through the electrolyte; instead, a chemical
reaction occurs at the cathode consuming electrons from the anode,
and another reaction occurs at the anode producing electrons to be
taken up by the cathode. As a result, a negative charge cloud
develops in the electrolyte around the cathode, and a positive
charge develops around the anode. The ions in the electrolyte move
to neutralize these charges so that the reactions can continue and
the electrons can keep flowing.
For example, in a solution of ordinary salt ( sodium chloride ,
NaCl) in water, the cathode reaction will be
2H 2 O + 2e − → 2OH − + H 2
and hydrogen gas will bubble up; the anode reaction is
2H 2 O → O 2 + 4H + + 4e −
and oxygen gas will be liberated. The positively charged sodium
ions Na + will react towards the cathode neutralizing the negative
charge of OH − there, and the negatively charged chlorine
ions Cl − will react towards the anode neutralizing the
positive charge of H + there. Without the ions from the
electrolyte, the charges around the electrode would slow down
continued electron flow; diffusion of H + and OH − through
water to the other electrode takes longer than movement of the much
more prevalent salt ions.
In other systems, the electrode reactions can involve the metals of
the electrodes as well as the ions of the electrolyte.
Electrolytic conductors are used in electronic devices where the
chemical reaction at a metal/electrolyte interface yields useful
effects.
In batteries , two metals with different electron affinities are
used as electrodes; electrons flow from one electrode to the other
outside of the battery, while inside the battery the circuit is
closed by the electrolyte's ions. Here the electrode reactions
convert chemical energy to electrical energy.
In some fuel cells , a solid electrolyte or proton conductor
connects the plates electrically while keeping the hydrogen and
oxygen fuel gases separated.
In electroplating tanks, the electrolyte simultaneously deposits
metal onto the object to be plated, and electrically connects that
object in the circuit.
In operation-hours gauges, two thin columns of mercury are
separated by a small electrolyte-filled gap, and, as charge is
passed through the device, the metal dissolves on one side and
plates out on the other, causing the visible gap to slowly move
along.
In electrolytic capacitors the chemical effect is used to produce
an extremely thin ' dielectric ' or insulating coating, while the
electrolyte layer behaves as one capacitor plate.
In some hygrometers the humidity of air is sensed by measuring the
conductivity of a nearly dry electrolyte.
Hot, softened glass is an electrolytic conductor, and some glass
manufacturers keep the glass molten by passing a large current
through it.
Dry electrolyte
Dry electrolytes are essentially gels in a flexible lattice
framework. [ 4 ]
See also
Strong electrolyte
ITIES (Interface between Two Immiscible Electrolyte Solutions)
A vitamin is an organic compound required as a nutrient in tiny
amounts by an organism . [ 1 ] The term 'vitamin' first became
popular in the early 1800s as a portmanteau of the words 'vital'
and 'mineral', though the actual meaning of the word has developed
somewhat since that time [ 2 ] . A compound is called a vitamin
when it cannot be synthesized in sufficient quantities by an
organism, and must be obtained from the diet. Thus, the term is
conditional both on the circumstances and the particular organism.
For example, ascorbic acid functions as vitamin C for some animals
but not others, and vitamins D , K and biotin are required in the
human diet only in certain circumstances. [ 3 ] The term vitamin
does not include other essential nutrients such as dietary minerals
, essential fatty acids , or essential amino acids , nor does it
encompass the large number of other nutrients that promote health
but are otherwise required less often. [ 4 ]
Vitamins are classified by their biological and chemical activity,
not their structure. Thus, each "vitamin" may refer to several
vitamer compounds that all show the biological activity associated
with a particular vitamin. Such a set of chemicals are grouped
under an alphabetized vitamin "generic descriptor" title, such as "
vitamin A ", which includes the compounds retinal , retinol , and
four known carotenoids . [ 5 ] Vitamers by definition are
convertable to the active form of the vitamin in the body, and are
sometimes inter-convertable to one another as well.
Vitamins have diverse biochemical functions. Some have hormone-like
functions as regulators of mineral metabolism (e.g. vitamin D), or
regulators of cell and tissue growth and differentiation (e.g. some
forms of vitamin A ). Others function as antioxidants (e.g. vitamin
E and sometimes vitamin C ). [ 6 ] The largest number of vitamins
(e.g. B complex vitamins) function as precursors for enzyme
cofactor bio-molecules ( coenzymes ), that help act as catalysts
and substrates in metabolism . When acting as part of a catalyst,
vitamins may be tightly bound to enzymes as part of prosthetic
groups : for example, biotin is part of enzymes involved in making
fatty acids . Vitamins may also be less tightly bound to enzyme
catalysts as coenzymes , detachable molecules which function to
carry chemical groups or electrons between molecules. For example,
folic acid carries various forms of carbon group – methyl ,
formyl and methylene - in the cell. Although these roles in
assisting enzyme reactions are vitamins' best-known function, the
other vitamin functions are equally important. [ 7 ]
Until the 1900s, vitamins were obtained solely through food intake,
and changes in diet (which, for example, could occur during a
particular growing season) can alter the types and amounts of
vitamins ingested. Vitamins have been produced as commodity
chemicals and made widely available as inexpensive pills for
several decades, [ 8 ] allowing supplementation of the dietary
intake.
Contents
1 History
2 In humans
2.1 List of vitamins
3 In nutrition and diseases
3.1 Deficiencies
3.2 Side effects and overdose
4 Supplements
4.1 Governmental regulation of vitamin supplements
5 Names in current and previous nomenclatures
6 See also
7 References
8 External links
//
History
The discovery of vitamins and their sources
Year of discovery
Vitamin
Food source
1913
Vitamin A ( Retinol )
Cod liver oil
1910
Vitamin B 1 ( Thiamine )
Rice bran
1920
Vitamin C ( Ascorbic acid )
Lemons
1920
Vitamin D ( Calciferol )
Cod liver oil
1920
Vitamin B 2 ( Riboflavin )
Eggs
1922
Vitamin E ( Tocopherol )
Wheat germ oil ,
Cosmetics and liver
1926
Vitamin B 12 (Cyanocobalamin)
Liver
1929
Vitamin K (Phylloquinone)
Alfalfa
1931
Vitamin B 5 ( Pantothenic acid )
Liver
1931
Vitamin B 7 ( Biotin )
Liver
1934
Vitamin B 6 ( Pyridoxine )
Rice bran
1936
Vitamin B 3 ( Niacin )
Liver
1941
Vitamin B 9 ( Folic acid )
Liver
The value of eating a certain food to maintain health was
recognized long before vitamins were identified. The ancient
Egyptians knew that feeding liver to a patient would help cure
night blindness , an illness now known to be caused by a vitamin A
deficiency. [ 9 ] The advancement of ocean voyage during the
Renaissance resulted in prolonged periods without access to fresh
fruits and vegetables, and made illnesses from vitamin deficiency
common among ships' crews. [ 10 ]
In 1749, the Scottish surgeon James Lind discovered that citrus
foods helped prevent scurvy , a particularly deadly disease in
which collagen is not properly formed, causing poor wound healing,
bleeding of the gums , severe pain, and death. [ 9 ] In 1753, Lind
published his Treatise on the Scurvy , which recommended using
lemons and limes to avoid scurvy , which was adopted by the British
Royal Navy . This led to the nickname Limey for sailors of that
organization. Lind's discovery, however, was not widely accepted by
individuals in the Royal Navy's Arctic expeditions in the 19th
century, where it was widely believed that scurvy could be
prevented by practicing good hygiene , regular exercise, and by
maintaining the morale of the crew while on board, rather than by a
diet of fresh food. [ 9 ] As a result, Arctic expeditions continued
to be plagued by scurvy and other deficiency diseases . In the
early 20th century, when Robert Falcon Scott made his two
expeditions to the Antarctic , the prevailing medical theory was
that scurvy was caused by "tainted" canned food . [ 9 ]
During the late 18th and early 19th centuries, the use of
deprivation studies allowed scientists to isolate and identify a
number of vitamins. Initially, lipid from fish oil was used to cure
rickets in rats , and the fat-soluble nutrient was called
"antirachitic A". Thus, the first "vitamin" bioactivity ever
isolated, which cured rickets, was initially called "vitamin A",
although confusingly the bioactivity of this compound is now called
vitamin D . [ 11 ] In 1881, Russian surgeon Nikolai Lunin studied
the effects of scurvy while at the University of Tartu in
present-day Estonia. [ 12 ] He fed mice an artificial mixture of
all the separate constituents of milk known at that time, namely
the proteins , fats , carbohydrates , and salts . The mice that
received only the individual constituents died, while the mice fed
by milk itself developed normally. He made a conclusion that "a
natural food such as milk must therefore contain, besides these
known principal ingredients, small quantities of unknown substances
essential to life." [ 12 ] However, his conclusions were rejected
by other researchers when they were unable to reproduce his
results. One difference was that he had used table sugar ( sucrose
), while other researchers had used milk sugar ( lactose ) that
still contained small amounts of vitamin B .
The Ancient Egyptians knew that feeding a patient liver (back,
right) would help cure night blindness .
In east Asia , where polished white rice was the common staple food
of the middle class, beriberi resulting from lack of vitamin B1 was
endemic. In 1884, Takaki Kanehiro , a British trained medical
doctor of the Imperial Japanese Navy , observed that beriberi was
endemic among low-ranking crew who often ate nothing but rice, but
not among officers who consumed a Western-style diet. With the
support of the Japanese navy, he experimented using crews of two
battleships ; one crew was fed only white rice, while the other was
fed a diet of meat, fish, barley, rice, and beans. The group that
ate only white rice documented 161 crew members with beriberi and
25 deaths, while the latter group had only 14 cases of beriberi and
no deaths. This convinced Takaki and the Japanese Navy that diet
was the cause of beriberi, but mistakenly believed that sufficient
amounts of protein prevented it. [ 13 ] That diseases could result
from some dietary deficiencies was further investigated by
Christiaan Eijkman , who in 1897 discovered that feeding unpolished
rice instead of the polished variety to chickens helped to prevent
beriberi in the chickens. The following year, Frederick Hopkins
postulated that some foods contained "accessory factors"—in
addition to proteins, carbohydrates, fats, et cetera—that
were necessary for the functions of the human body. [ 9 ] Hopkins
and Eijkman were awarded the Nobel Prize for Physiology or Medicine
in 1929 for their discovery of several vitamins. [ 14 ]
In 1910, the first vitamin was founded by Japanese scientist
Umetaro Suzuki who succeeded in extracting a water-soluble complex
of micronutrients from rice bran and named it aberic acid (later
Orizanin). He published this discovery in a Japanese scientific
journal. [ 15 ] When the article was translated into German, the
translation failed to state that it was a newly discovered
nutrient, a claim made in the original Japanese article, and hence
his discovery failed to gain publicity. In 1912 Polish biochemist
Kazimierz Funk isolated the same complex of micronutrients and
proposed the complex be named "Vitamine" (a portmanteau of "vital
amine"). [ 16 ] The name soon became synonymous with Hopkins'
"accessory factors", and by the time it was shown that not all
vitamins were amines , the word was already ubiquitous. In 1920,
Jack Cecil Drummond proposed that the final "e" be dropped to
deemphasize the "amine" reference after the discovery that vitamin
C had no amine component. [ 13 ]
In 1931, Albert Szent-Györgyi and a fellow researcher Joseph
Svirbely determined that "hexuronic acid" was actually vitamin C
and noted its anti- scorbutic activity. In 1937, Szent-Györgyi
was awarded the Nobel Prize in Physiology or Medicine for his
discovery. In 1943 Edward Adelbert Doisy and Henrik Dam were
awarded the Nobel Prize in Physiology or Medicine for their
discovery of vitamin K and its chemical structure. In 1967, George
Wald was awarded the Nobel Prize (along with Ragnar Granit and
Haldan Keffer Hartline ) for his discovery that vitamin A could
participate directly in a physiological process. [ 14 ]
In humans
Vitamins are classified as either water -soluble or fat soluble. In
humans there are 13 vitamins: 4 fat-soluble (A, D, E and K) and 9
water-soluble (8 B vitamins and vitamin C). Water-soluble vitamins
dissolve easily in water, and in general, are readily excreted from
the body, to the degree that urinary output is a strong predictor
of vitamin consumption. [ 17 ] Because they are not readily stored,
consistent daily intake is important. [ 18 ] Many types of
water-soluble vitamins are synthesized by bacteria. [ 19 ] Fat
-soluble vitamins are absorbed through the intestinal tract with
the help of lipids (fats). Because they are more likely to
accumulate in the body, they are more likely to lead to
hypervitaminosis than are water-soluble vitamins. Fat-soluble
vitamin regulation is of particular significance in cystic fibrosis
. [ 20 ]
List of vitamins
Each vitamin is typically used in multiple reactions and,
therefore, most have multiple functions. [ 21 ]
Vitamin generic
descriptor name
Vitamer chemical name(s) (list not complete)
Solubility
Recommended dietary allowances
(male, age 19–70) [ 22 ]
Deficiency disease
Upper Intake Level
(UL/day) [ 22 ]
Overdose disease
Vitamin A
Retinol , retinal , various retinoids , and
four carotenoids )
Fat
900 µg
Night-blindness and
Keratomalacia [ 23 ]
3,000 µg
Hypervitaminosis A
Vitamin B 1
Thiamine
Water
1.2 mg
Beriberi , Wernicke-Korsakoff syndrome
N/D [ 24 ]
Drowsiness or muscle relaxation with large doses. [ 25 ]
Vitamin B 2
Riboflavin
Water
1.3 mg
Ariboflavinosis
N/D
Vitamin B 3
Niacin , niacinamide
Water
16.0 mg
Pellagra
35.0 mg
Liver damage (doses > 2g/day) [ 26 ] and other problems
Vitamin B 5
Pantothenic acid
Water
5.0 mg [ 27 ]
Paresthesia
N/D
Diarrhea; possibly nausea and heartburn. [ 28 ]
Vitamin B 6
Pyridoxine , pyridoxamine , pyridoxal
Water
1.3–1.7 mg
Anemia [ 29 ] peripheral neuropathy .
100 mg
Impairment of proprioception , nerve damage (doses >
100 mg/day)
Vitamin B 7
Biotin
Water
30.0 µg
Dermatitis , enteritis
N/D
Vitamin B 9
Folic acid , folinic acid
Water
400 µg
Deficiency during pregnancy is associated with birth defects , such
as neural tube defects
1,000 µg
May mask symptoms of vitamin B 12 deficiency; other effects .
Vitamin B 12
Cyanocobalamin , hydroxycobalamin , methylcobalamin
Water
2.4 µg
Megaloblastic anemia [ 30 ]
N/D
No known toxicity [ 30 ]
Vitamin C
Ascorbic acid
Water
90.0 mg
Scurvy
2,000 mg
Vitamin C megadosage
Vitamin D
Ergocalciferol , cholecalciferol
Fat
5.0 µg–10 µg [ 31 ]
Rickets and Osteomalacia
50 µg
Hypervitaminosis D
Vitamin E
Tocopherols , tocotrienols
Fat
15.0 mg
Deficiency is very rare; mild hemolytic anemia in newborn infants.
[ 32 ]
1,000 mg
Increased congestive heart failure seen in one large randomized
study. [ 33 ]
In nutrition and diseases
Vitamins are essential for the normal growth and development of a
multicellular organism. Using the genetic blueprint inherited from
its parents, a fetus begins to develop, at the moment of
conception, from the nutrients it absorbs. It requires certain
vitamins and minerals to be present at certain times. These
nutrients facilitate the chemical reactions that produce among
other things, skin , bone , and muscle . If there is serious
deficiency in one or more of these nutrients, a child may develop a
deficiency disease. Even minor deficiencies may cause permanent
damage. [ 35 ]
For the most part, vitamins are obtained with food, but a few are
obtained by other means. For example, microorganisms in the
intestine—commonly known as " gut flora "—produce
vitamin K and biotin, while one form of vitamin D is synthesized in
the skin with the help of the natural ultraviolet wavelength of
sunlight . Humans can produce some vitamins from precursors they
consume. Examples include vitamin A , produced from beta carotene ,
and niacin, from the amino acid tryptophan . [ 22 ]
Once growth and development are completed, vitamins remain
essential nutrients for the healthy maintenance of the cells,
tissues, and organs that make up a multicellular organism; they
also enable a multicellular life form to efficiently use chemical
energy provided by food it eats, and to help process the proteins,
carbohydrates, and fats required for respiration. [ 6 ]
Deficiencies
Because human bodies do not store most vitamins, humans must
consume them regularly to avoid deficiency. Human bodily stores for
different vitamins vary widely; vitamins A, D, and B 12 are stored
in significant amounts in the human body, mainly in the liver , [
32 ] and an adult human's diet may be deficient in vitamins A and B
12 for many months before developing a deficiency condition.
Vitamin B 3 is not stored in the human body in significant amounts,
so stores may only last a couple of weeks. [ 23 ] [ 32 ]
Deficiencies of vitamins are classified as either primary or
secondary. A primary deficiency occurs when an organism does not
get enough of the vitamin in its food. A secondary deficiency may
be due to an underlying disorder that prevents or limits the
absorption or use of the vitamin, due to a “lifestyle
factor”, such as smoking, excessive alcohol consumption, or
the use of medications that interfere with the absorption or use of
the vitamin. [ 32 ] People who eat a varied diet are unlikely to
develop a severe primary vitamin deficiency. In contrast,
restrictive diets have the potential to cause prolonged vitamin
deficits, which may result in often painful and potentially deadly
diseases .
Well-known human vitamin deficiencies involve thiamine ( beriberi
), niacin ( pellagra ), vitamin C ( scurvy ) and vitamin D (
rickets ). In much of the developed world, such deficiencies are
rare; this is due to (1) an adequate supply of food; and (2) the
addition of vitamins and minerals to common foods, often called
fortification. [ 22 ] [ 32 ] In addition to these classical vitamin
deficiency diseases, some evidence has also suggested links between
vitamin deficiency and a number of different disorders. [ 36 ] [ 37
]
Side effects and overdose
In large doses, some vitamins have documented side effects that
tend to be more severe with a larger dosage. The likelihood of
consuming too much of any vitamin from food is remote, but
overdosing from vitamin supplementation does occur. At high enough
dosages some vitamins cause side effects such as nausea , diarrhea
, and vomiting . [ 23 ] [ 38 ]
When side effects emerge, recovery is often accomplished by
reducing the dosage. The concentrations of vitamins an individual
can tolerate vary widely, and appear to be related to age and state
of health. [ 39 ] In the United States, overdose exposure to all
formulations of vitamins was reported by 62,562 individuals in 2004
(nearly 80% of these exposures were in children under the age of
6), leading to 53 "major" life-threatening outcomes and 3 deaths [
40 ] ;a small number in comparison to the 19,250 people who died of
unintentional poisoning of all kinds in the U.S. in the same year
(2004). [ 41 ]
Supplements
Dietary supplements , often containing vitamins, are used to ensure
that adequate amounts of nutrients are obtained on a daily basis,
if optimal amounts of the nutrients cannot be obtained through a
varied diet. Scientific evidence supporting the benefits of some
vitamin supplements is well established for certain health
conditions, but others need further study. [ 42 ] In some cases,
vitamin supplements may have unwanted effects, especially if taken
before surgery, with other dietary supplements or medicines, or if
the person taking them has certain health conditions. [ 42 ]
Dietary supplements may also contain levels of vitamins many times
higher, and in different forms, than one may ingest through food. [
43 ]
A meta-analysis published in 2006 suggested that Vitamin A and E
supplements not only provide no tangible health benefits for
generally healthy individuals, but may actually increase mortality,
although two large studies included in the analysis involved
smokers , for which it was already known that beta-carotene
supplements can be harmful. [ 44 ] Another study released in May
2009 found that antioxidants such as vitamins C and E may actually
curb some benefits of exercise. [ 45 ]
Governmental regulation of vitamin supplements
Most countries place dietary supplements in a special category
under the general umbrella of foods , not drugs. This necessitates
that the manufacturer, and not the government, be responsible for
ensuring that its dietary supplement products are safe before they
are marketed. Unlike drug products, which must explicitly be proven
safe and effective for their intended use before marketing, there
are often no provisions to "approve" dietary supplements for safety
or effectiveness before they reach the consumer. Also unlike drug
products, manufacturers and distributors of dietary supplements are
not generally required to report any claims of injuries or
illnesses that may be related to the use of their products. [ 46 ]
[ 47 ] [ 42 ]
Names in current and previous nomenclatures
Nomenclature of reclassified vitamins
Previous name
Chemical name
Reason for name change [ 48 ]
Vitamin B 4
Adenine
DNA metabolite
Vitamin B 8
Adenylic acid
DNA metabolite
Vitamin F
Essential fatty acids
Needed in large quantities (does
not fit the definition of a vitamin).
Vitamin G
Riboflavin
Reclassified as Vitamin B 2
Vitamin H
Biotin
Reclassified as Vitamin B 7
Vitamin J
Catechol , Flavin
Protein metabolite
Vitamin L 1 [ 49 ]
Anthranilic acid
Protein metabolite
Vitamin L 2 [ 49 ]
Adenylthiomethylpentose
RNA metabolite
Vitamin M
Folic acid
Reclassified as Vitamin B 9
Vitamin O
Carnitine
Protein metabolite
Vitamin P
Flavonoids
No longer classified as a vitamin
Vitamin PP
Niacin
Reclassified as Vitamin B 3
Vitamin U
S-Methylmethionine
Protein metabolite
The reason the set of vitamins seems to skip directly from E to K
is that the vitamins corresponding to letters F-J were either
reclassified over time, discarded as false leads, or renamed
because of their relationship to vitamin B, which became a complex
of vitamins.
The German-speaking scientists who isolated and described vitamin K
(in addition to naming it as such) did so because the vitamin is
intimately involved in the Koagulation of blood following wounding.
At the time, most (but not all) of the letters from F through to J
were already designated, so the use of the letter K was considered
quite reasonable. [ 48 ] [ 50 ] The table on the right lists
chemicals that had previously been classified as vitamins, as well
as the earlier names of vitamins that later became part of the
B-complex.
A vitamin is an organic compound required as a nutrient in tiny
amounts by an organism . [ 1 ] The term 'vitamin' first became
popular in the early 1800s as a portmanteau of the words 'vital'
and 'mineral', though the actual meaning of the word has developed
somewhat since that time [ 2 ] . A compound is called a vitamin
when it cannot be synthesized in sufficient quantities by an
organism, and must be obtained from the diet. Thus, the term is
conditional both on the circumstances and the particular organism.
For example, ascorbic acid functions as vitamin C for some animals
but not others, and vitamins D , K and biotin are required in the
human diet only in certain circumstances. [ 3 ] The term vitamin
does not include other essential nutrients such as dietary minerals
, essential fatty acids , or essential amino acids , nor does it
encompass the large number of other nutrients that promote health
but are otherwise required less often. [ 4 ]
Vitamins are classified by their biological and chemical activity,
not their structure. Thus, each "vitamin" may refer to several
vitamer compounds that all show the biological activity associated
with a particular vitamin. Such a set of chemicals are grouped
under an alphabetized vitamin "generic descriptor" title, such as "
vitamin A ", which includes the compounds retinal , retinol , and
four known carotenoids . [ 5 ] Vitamers by definition are
convertable to the active form of the vitamin in the body, and are
sometimes inter-convertable to one another as well.
Vitamins have diverse biochemical functions. Some have hormone-like
functions as regulators of mineral metabolism (e.g. vitamin D), or
regulators of cell and tissue growth and differentiation (e.g. some
forms of vitamin A ). Others function as antioxidants (e.g. vitamin
E and sometimes vitamin C ). [ 6 ] The largest number of vitamins
(e.g. B complex vitamins) function as precursors for enzyme
cofactor bio-molecules ( coenzymes ), that help act as catalysts
and substrates in metabolism . When acting as part of a catalyst,
vitamins may be tightly bound to enzymes as part of prosthetic
groups : for example, biotin is part of enzymes involved in making
fatty acids . Vitamins may also be less tightly bound to enzyme
catalysts as coenzymes , detachable molecules which function to
carry chemical groups or electrons between molecules. For example,
folic acid carries various forms of carbon group – methyl ,
formyl and methylene - in the cell. Although these roles in
assisting enzyme reactions are vitamins' best-known function, the
other vitamin functions are equally important. [ 7 ]
Until the 1900s, vitamins were obtained solely through food intake,
and changes in diet (which, for example, could occur during a
particular growing season) can alter the types and amounts of
vitamins ingested. Vitamins have been produced as commodity
chemicals and made widely available as inexpensive pills for
several decades, [ 8 ] allowing supplementation of the dietary
intake.
Contents
1 History
2 In humans
2.1 List of vitamins
3 In nutrition and diseases
3.1 Deficiencies
3.2 Side effects and overdose
4 Supplements
4.1 Governmental regulation of vitamin supplements
5 Names in current and previous nomenclatures
6 See also
7 References
8 External links
//
History
The discovery of vitamins and their sources
Year of discovery
Vitamin
Food source
1913
Vitamin A ( Retinol )
Cod liver oil
1910
Vitamin B 1 ( Thiamine )
Rice bran
1920
Vitamin C ( Ascorbic acid )
Lemons
1920
Vitamin D ( Calciferol )
Cod liver oil
1920
Vitamin B 2 ( Riboflavin )
Eggs
1922
Vitamin E ( Tocopherol )
Wheat germ oil ,
Cosmetics and liver
1926
Vitamin B 12 (Cyanocobalamin)
Liver
1929
Vitamin K (Phylloquinone)
Alfalfa
1931
Vitamin B 5 ( Pantothenic acid )
Liver
1931
Vitamin B 7 ( Biotin )
Liver
1934
Vitamin B 6 ( Pyridoxine )
Rice bran
1936
Vitamin B 3 ( Niacin )
Liver
1941
Vitamin B 9 ( Folic acid )
Liver
The value of eating a certain food to maintain health was
recognized long before vitamins were identified. The ancient
Egyptians knew that feeding liver to a patient would help cure
night blindness , an illness now known to be caused by a vitamin A
deficiency. [ 9 ] The advancement of ocean voyage during the
Renaissance resulted in prolonged periods without access to fresh
fruits and vegetables, and made illnesses from vitamin deficiency
common among ships' crews. [ 10 ]
In 1749, the Scottish surgeon James Lind discovered that citrus
foods helped prevent scurvy , a particularly deadly disease in
which collagen is not properly formed, causing poor wound healing,
bleeding of the gums , severe pain, and death. [ 9 ] In 1753, Lind
published his Treatise on the Scurvy , which recommended using
lemons and limes to avoid scurvy , which was adopted by the British
Royal Navy . This led to the nickname Limey for sailors of that
organization. Lind's discovery, however, was not widely accepted by
individuals in the Royal Navy's Arctic expeditions in the 19th
century, where it was widely believed that scurvy could be
prevented by practicing good hygiene , regular exercise, and by
maintaining the morale of the crew while on board, rather than by a
diet of fresh food. [ 9 ] As a result, Arctic expeditions continued
to be plagued by scurvy and other deficiency diseases . In the
early 20th century, when Robert Falcon Scott made his two
expeditions to the Antarctic , the prevailing medical theory was
that scurvy was caused by "tainted" canned food . [ 9 ]
During the late 18th and early 19th centuries, the use of
deprivation studies allowed scientists to isolate and identify a
number of vitamins. Initially, lipid from fish oil was used to cure
rickets in rats , and the fat-soluble nutrient was called
"antirachitic A". Thus, the first "vitamin" bioactivity ever
isolated, which cured rickets, was initially called "vitamin A",
although confusingly the bioactivity of this compound is now called
vitamin D . [ 11 ] In 1881, Russian surgeon Nikolai Lunin studied
the effects of scurvy while at the University of Tartu in
present-day Estonia. [ 12 ] He fed mice an artificial mixture of
all the separate constituents of milk known at that time, namely
the proteins , fats , carbohydrates , and salts . The mice that
received only the individual constituents died, while the mice fed
by milk itself developed normally. He made a conclusion that "a
natural food such as milk must therefore contain, besides these
known principal ingredients, small quantities of unknown substances
essential to life." [ 12 ] However, his conclusions were rejected
by other researchers when they were unable to reproduce his
results. One difference was that he had used table sugar ( sucrose
), while other researchers had used milk sugar ( lactose ) that
still contained small amounts of vitamin B .
The Ancient Egyptians knew that feeding a patient liver (back,
right) would help cure night blindness .
In east Asia , where polished white rice was the common staple food
of the middle class, beriberi resulting from lack of vitamin B1 was
endemic. In 1884, Takaki Kanehiro , a British trained medical
doctor of the Imperial Japanese Navy , observed that beriberi was
endemic among low-ranking crew who often ate nothing but rice, but
not among officers who consumed a Western-style diet. With the
support of the Japanese navy, he experimented using crews of two
battleships ; one crew was fed only white rice, while the other was
fed a diet of meat, fish, barley, rice, and beans. The group that
ate only white rice documented 161 crew members with beriberi and
25 deaths, while the latter group had only 14 cases of beriberi and
no deaths. This convinced Takaki and the Japanese Navy that diet
was the cause of beriberi, but mistakenly believed that sufficient
amounts of protein prevented it. [ 13 ] That diseases could result
from some dietary deficiencies was further investigated by
Christiaan Eijkman , who in 1897 discovered that feeding unpolished
rice instead of the polished variety to chickens helped to prevent
beriberi in the chickens. The following year, Frederick Hopkins
postulated that some foods contained "accessory factors"—in
addition to proteins, carbohydrates, fats, et cetera—that
were necessary for the functions of the human body. [ 9 ] Hopkins
and Eijkman were awarded the Nobel Prize for Physiology or Medicine
in 1929 for their discovery of several vitamins. [ 14 ]
In 1910, the first vitamin was founded by Japanese scientist
Umetaro Suzuki who succeeded in extracting a water-soluble complex
of micronutrients from rice bran and named it aberic acid (later
Orizanin). He published this discovery in a Japanese scientific
journal. [ 15 ] When the article was translated into German, the
translation failed to state that it was a newly discovered
nutrient, a claim made in the original Japanese article, and hence
his discovery failed to gain publicity. In 1912 Polish biochemist
Kazimierz Funk isolated the same complex of micronutrients and
proposed the complex be named "Vitamine" (a portmanteau of "vital
amine"). [ 16 ] The name soon became synonymous with Hopkins'
"accessory factors", and by the time it was shown that not all
vitamins were amines , the word was already ubiquitous. In 1920,
Jack Cecil Drummond proposed that the final "e" be dropped to
deemphasize the "amine" reference after the discovery that vitamin
C had no amine component. [ 13 ]
In 1931, Albert Szent-Györgyi and a fellow researcher Joseph
Svirbely determined that "hexuronic acid" was actually vitamin C
and noted its anti- scorbutic activity. In 1937, Szent-Györgyi
was awarded the Nobel Prize in Physiology or Medicine for his
discovery. In 1943 Edward Adelbert Doisy and Henrik Dam were
awarded the Nobel Prize in Physiology or Medicine for their
discovery of vitamin K and its chemical structure. In 1967, George
Wald was awarded the Nobel Prize (along with Ragnar Granit and
Haldan Keffer Hartline ) for his discovery that vitamin A could
participate directly in a physiological process. [ 14 ]
In humans
Vitamins are classified as either water -soluble or fat soluble. In
humans there are 13 vitamins: 4 fat-soluble (A, D, E and K) and 9
water-soluble (8 B vitamins and vitamin C). Water-soluble vitamins
dissolve easily in water, and in general, are readily excreted from
the body, to the degree that urinary output is a strong predictor
of vitamin consumption. [ 17 ] Because they are not readily stored,
consistent daily intake is important. [ 18 ] Many types of
water-soluble vitamins are synthesized by bacteria. [ 19 ] Fat
-soluble vitamins are absorbed through the intestinal tract with
the help of lipids (fats). Because they are more likely to
accumulate in the body, they are more likely to lead to
hypervitaminosis than are water-soluble vitamins. Fat-soluble
vitamin regulation is of particular significance in cystic fibrosis
. [ 20 ]
List of vitamins
Each vitamin is typically used in multiple reactions and,
therefore, most have multiple functions. [ 21 ]
Vitamin generic
descriptor name
Vitamer chemical name(s) (list not complete)
Solubility
Recommended dietary allowances
(male, age 19–70) [ 22 ]
Deficiency disease
Upper Intake Level
(UL/day) [ 22 ]
Overdose disease
Vitamin A
Retinol , retinal , various retinoids , and
four carotenoids )
Fat
900 µg
Night-blindness and
Keratomalacia [ 23 ]
3,000 µg
Hypervitaminosis A
Vitamin B 1
Thiamine
Water
1.2 mg
Beriberi , Wernicke-Korsakoff syndrome
N/D [ 24 ]
Drowsiness or muscle relaxation with large doses. [ 25 ]
Vitamin B 2
Riboflavin
Water
1.3 mg
Ariboflavinosis
N/D
Vitamin B 3
Niacin , niacinamide
Water
16.0 mg
Pellagra
35.0 mg
Liver damage (doses > 2g/day) [ 26 ] and other problems
Vitamin B 5
Pantothenic acid
Water
5.0 mg [ 27 ]
Paresthesia
N/D
Diarrhea; possibly nausea and heartburn. [ 28 ]
Vitamin B 6
Pyridoxine , pyridoxamine , pyridoxal
Water
1.3–1.7 mg
Anemia [ 29 ] peripheral neuropathy .
100 mg
Impairment of proprioception , nerve damage (doses >
100 mg/day)
Vitamin B 7
Biotin
Water
30.0 µg
Dermatitis , enteritis
N/D
Vitamin B 9
Folic acid , folinic acid
Water
400 µg
Deficiency during pregnancy is associated with birth defects , such
as neural tube defects
1,000 µg
May mask symptoms of vitamin B 12 deficiency; other effects .
Vitamin B 12
Cyanocobalamin , hydroxycobalamin , methylcobalamin
Water
2.4 µg
Megaloblastic anemia [ 30 ]
N/D
No known toxicity [ 30 ]
Vitamin C
Ascorbic acid
Water
90.0 mg
Scurvy
2,000 mg
Vitamin C megadosage
Vitamin D
Ergocalciferol , cholecalciferol
Fat
5.0 µg–10 µg [ 31 ]
Rickets and Osteomalacia
50 µg
Hypervitaminosis D
Vitamin E
Tocopherols , tocotrienols
Fat
15.0 mg
Deficiency is very rare; mild hemolytic anemia in newborn infants.
[ 32 ]
1,000 mg
Increased congestive heart failure seen in one large randomized
study. [ 33 ]
In nutrition and diseases
Vitamins are essential for the normal growth and development of a
multicellular organism. Using the genetic blueprint inherited from
its parents, a fetus begins to develop, at the moment of
conception, from the nutrients it absorbs. It requires certain
vitamins and minerals to be present at certain times. These
nutrients facilitate the chemical reactions that produce among
other things, skin , bone , and muscle . If there is serious
deficiency in one or more of these nutrients, a child may develop a
deficiency disease. Even minor deficiencies may cause permanent
damage. [ 35 ]
For the most part, vitamins are obtained with food, but a few are
obtained by other means. For example, microorganisms in the
intestine—commonly known as " gut flora "—produce
vitamin K and biotin, while one form of vitamin D is synthesized in
the skin with the help of the natural ultraviolet wavelength of
sunlight . Humans can produce some vitamins from precursors they
consume. Examples include vitamin A , produced from beta carotene ,
and niacin, from the amino acid tryptophan . [ 22 ]
Once growth and development are completed, vitamins remain
essential nutrients for the healthy maintenance of the cells,
tissues, and organs that make up a multicellular organism; they
also enable a multicellular life form to efficiently use chemical
energy provided by food it eats, and to help process the proteins,
carbohydrates, and fats required for respiration. [ 6 ]
Deficiencies
Because human bodies do not store most vitamins, humans must
consume them regularly to avoid deficiency. Human bodily stores for
different vitamins vary widely; vitamins A, D, and B 12 are stored
in significant amounts in the human body, mainly in the liver , [
32 ] and an adult human's diet may be deficient in vitamins A and B
12 for many months before developing a deficiency condition.
Vitamin B 3 is not stored in the human body in significant amounts,
so stores may only last a couple of weeks. [ 23 ] [ 32 ]
Deficiencies of vitamins are classified as either primary or
secondary. A primary deficiency occurs when an organism does not
get enough of the vitamin in its food. A secondary deficiency may
be due to an underlying disorder that prevents or limits the
absorption or use of the vitamin, due to a “lifestyle
factor”, such as smoking, excessive alcohol consumption, or
the use of medications that interfere with the absorption or use of
the vitamin. [ 32 ] People who eat a varied diet are unlikely to
develop a severe primary vitamin deficiency. In contrast,
restrictive diets have the potential to cause prolonged vitamin
deficits, which may result in often painful and potentially deadly
diseases .
Well-known human vitamin deficiencies involve thiamine ( beriberi
), niacin ( pellagra ), vitamin C ( scurvy ) and vitamin D (
rickets ). In much of the developed world, such deficiencies are
rare; this is due to (1) an adequate supply of food; and (2) the
addition of vitamins and minerals to common foods, often called
fortification. [ 22 ] [ 32 ] In addition to these classical vitamin
deficiency diseases, some evidence has also suggested links between
vitamin deficiency and a number of different disorders. [ 36 ] [ 37
]
Side effects and overdose
In large doses, some vitamins have documented side effects that
tend to be more severe with a larger dosage. The likelihood of
consuming too much of any vitamin from food is remote, but
overdosing from vitamin supplementation does occur. At high enough
dosages some vitamins cause side effects such as nausea , diarrhea
, and vomiting . [ 23 ] [ 38 ]
When side effects emerge, recovery is often accomplished by
reducing the dosage. The concentrations of vitamins an individual
can tolerate vary widely, and appear to be related to age and state
of health. [ 39 ] In the United States, overdose exposure to all
formulations of vitamins was reported by 62,562 individuals in 2004
(nearly 80% of these exposures were in children under the age of
6), leading to 53 "major" life-threatening outcomes and 3 deaths [
40 ] ;a small number in comparison to the 19,250 people who died of
unintentional poisoning of all kinds in the U.S. in the same year
(2004). [ 41 ]
Supplements
Dietary supplements , often containing vitamins, are used to ensure
that adequate amounts of nutrients are obtained on a daily basis,
if optimal amounts of the nutrients cannot be obtained through a
varied diet. Scientific evidence supporting the benefits of some
vitamin supplements is well established for certain health
conditions, but others need further study. [ 42 ] In some cases,
vitamin supplements may have unwanted effects, especially if taken
before surgery, with other dietary supplements or medicines, or if
the person taking them has certain health conditions. [ 42 ]
Dietary supplements may also contain levels of vitamins many times
higher, and in different forms, than one may ingest through food. [
43 ]
A meta-analysis published in 2006 suggested that Vitamin A and E
supplements not only provide no tangible health benefits for
generally healthy individuals, but may actually increase mortality,
although two large studies included in the analysis involved
smokers , for which it was already known that beta-carotene
supplements can be harmful. [ 44 ] Another study released in May
2009 found that antioxidants such as vitamins C and E may actually
curb some benefits of exercise. [ 45 ]
Governmental regulation of vitamin supplements
Most countries place dietary supplements in a special category
under the general umbrella of foods , not drugs. This necessitates
that the manufacturer, and not the government, be responsible for
ensuring that its dietary supplement products are safe before they
are marketed. Unlike drug products, which must explicitly be proven
safe and effective for their intended use before marketing, there
are often no provisions to "approve" dietary supplements for safety
or effectiveness before they reach the consumer. Also unlike drug
products, manufacturers and distributors of dietary supplements are
not generally required to report any claims of injuries or
illnesses that may be related to the use of their products. [ 46 ]
[ 47 ] [ 42 ]
Names in current and previous nomenclatures
Nomenclature of reclassified vitamins
Previous name
Chemical name
Reason for name change [ 48 ]
Vitamin B 4
Adenine
DNA metabolite
Vitamin B 8
Adenylic acid
DNA metabolite
Vitamin F
Essential fatty acids
Needed in large quantities (does
not fit the definition of a vitamin).
Vitamin G
Riboflavin
Reclassified as Vitamin B 2
Vitamin H
Biotin
Reclassified as Vitamin B 7
Vitamin J
Catechol , Flavin
Protein metabolite
Vitamin L 1 [ 49 ]
Anthranilic acid
Protein metabolite
Vitamin L 2 [ 49 ]
Adenylthiomethylpentose
RNA metabolite
Vitamin M
Folic acid
Reclassified as Vitamin B 9
Vitamin O
Carnitine
Protein metabolite
Vitamin P
Flavonoids
No longer classified as a vitamin
Vitamin PP
Niacin
Reclassified as Vitamin B 3
Vitamin U
S-Methylmethionine
Protein metabolite
The reason the set of vitamins seems to skip directly from E to K
is that the vitamins corresponding to letters F-J were either
reclassified over time, discarded as false leads, or renamed
because of their relationship to vitamin B, which became a complex
of vitamins.
The German-speaking scientists who isolated and described vitamin K
(in addition to naming it as such) did so because the vitamin is
intimately involved in the Koagulation of blood following wounding.
At the time, most (but not all) of the letters from F through to J
were already designated, so the use of the letter K was considered
quite reasonable. [ 48 ] [ 50 ] The table on the right lists
chemicals that had previously been classified as vitamins, as well
as the earlier names of vitamins that later became part of the
B-complex.
Health is the general condition of a person in all aspects. It is
also a level of functional and/or metabolic efficiency of an
organism, often implicitly human .
At the time of the creation of the World Health Organization (WHO),
in 1948, health was defined as being "a state of complete physical,
mental, and social well-being and not merely the absence of disease
or infirmity". [ 1 ] [ 2 ]
Only a handful of publications have focused specifically on the
definition of health and its evolution in the first 6 decades. Some
of them highlight its lack of operational value and the problem
created by use of the word "complete." Others declare the
definition, which has not been modified since 1948, "simply a bad
one." [1]
In 1986, the WHO, in the Ottawa Charter for Health Promotion , said
that health is "a resource for everyday life, not the objective of
living. Health is a positive concept emphasizing social and
personal resources, as well as physical capacities." Classification
systems such as the WHO Family of International Classifications
(WHO-FIC), which is composed of the International Classification of
Functioning, Disability, and Health (ICF) and the International
Classification of Diseases (ICD) also define health.
Overall health is achieved through a combination of physical,
mental, emotional, and social well-being, which, together is
commonly referred to as the Health Triangle.
Contents
1 Determinants of health
2 Maintaining health
2.1 Social Activity
2.2 Hygiene
2.3 Stress management
2.4 Health care
2.4.1 Workplace wellness programs
3 Public health
4 Role of science in health
4.1 Sources
4.2 Application
5 See also
6 Notes
7 References
8 External links
//
Determinants of health
Main article: Social determinants of health
The LaLonde report suggests that there are four general
determinants of health including human biology , environment ,
lifestyle , and healthcare services . [ 3 ] Thus, health is
maintained and improved not only through the advancement and
application of health science , but also through the efforts and
intelligent lifestyle choices of the individual and society.
A major environmental factor is water quality, especially for the
health of infants and children in developing countries . [ 4 ]
Studies show that in developed countries , the lack of neighborhood
recreational space that includes the natural environment leads to
lower levels of neighborhood satisfaction and higher levels of
obesity; therefore, lower overall well being. [ 5 ] Therefore, the
positive psychological benefits of natural space in urban
neighborhoods should be taken into account in public policy and
land use. Health is also a state of complete
physical,mental,social,and spiritual wellbeing not merely absence
of disease.
Maintaining health
Main article: Self care
Achieving health and maintaining healthy is an ongoing process.
Effective strategies for staying healthy and improving one's health
include the following elements:
Social Activity
Main article: Social relation
Personal health depends partially on the social structure of one's
life. The maintenance of strong social relationships is linked to
good health conditions, longevity, productivity, and a positive
attitude. This is due to the fact that positive social interaction
as viewed by the participant increases many chemical levels in the
brain which are linked to personality and intelligence traits.
Volunteering also can lead to a healthy life. To be a volunteer,
while gaining plenty of social benefits, people also take their
mind off their own troubles. [ citation needed ] Volunteering could
even add years of life. According to a university study, [ citation
needed ] compared with people who did not volunteer, senior
citizens who volunteered showed a 67% reduced risk of dying during
a seven-year period.
Hygiene
Main article: Hygiene
Hygiene is the practice of keeping the body clean to prevent
infection and illness, and the avoidance of contact with infectious
agents. Hygiene practices include bathing , brushing and flossing
teeth , washing hands especially before eating, washing food before
it is eaten, cleaning food preparation utensils and surfaces before
and after preparing meals, and many others. This may help prevent
infection and illness. By cleaning the body, dead skin cells are
washed away with the germs, reducing their chance of entering the
body.
Stress management
Main article: Stress management
This section does not cite any references or sources .
Please help improve this article by adding citations to reliable
sources . Unsourced material may be challenged and removed . (May
2009)
Prolonged psychological stress may negatively impact health, and
has been cited as a factor in cognitive impairment with aging,
depressive illness, and expression of disease. [ 6 ] . Stress
management is the application of methods to either reduce stress or
increase tolerance to stress. Relaxation techniques are physical
methods used to relieve stress. Psychological methods include
cognitive therapy , meditation , and positive thinking which work
by reducing response to stress. Improving relevant skills and
abilities builds confidence, which also reduces the stress reaction
to situations where those skills are applicable.
Reducing uncertainty, by increasing knowledge and experience
related to stress-causing situations, has the same effect. Learning
to cope with problems better, such as improving problem solving and
time management skills, may also reduce stressful reaction to
problems. Repeatedly facing an object of one's fears may also
desensitize the fight-or-flight response with respect to that
stimulus—e.g., facing bullies may reduce fear of bullies.
Health care
Main article: Health care
Health care is the prevention, treatment, and management of illness
and the preservation of mental and physical well being through the
services offered by the medical , nursing , and allied health
professions.
Workplace wellness programs
Main article: Workplace wellness
Workplace wellness programs are recognized by an increasingly large
number of companies for their value in improving the health and
well-being of their employees, and for increasing morale, loyalty,
and productivity. [ citation needed ] Workplace wellness programs
can include things like onsite fitness centers, health
presentations, wellness newsletters, access to health coaching,
tobacco cessation programs and training related to nutrition ,
weight and stress management. Other programs may include health
risk assessments, health screenings and body mass index
monitoring.
Public health
Main article: Public health
Public health is "the science and art of preventing disease,
prolonging life and promoting health through the organised efforts
and informed choices of society, organizations, public and private,
communities and individuals." (Winslow, 1920) [ citation needed ]
It is concerned with threats to the overall health of a community
based on population health analysis. The population in question can
be as small as a handful of people or as large as all the
inhabitants of several continents (for instance, in the case of a
pandemic ). Public health has many sub-fields, but is typically
divided into the categories of epidemiology , biostatistics and
health services . Environmental , social and behavioral health, and
occupational health , are also important fields in public
health.
The focus of public health intervention is to prevent rather than
treat a disease through surveillance of cases and the promotion of
healthy behaviors. In addition to these activities, in many cases
treating a disease can be vital to preventing it in others, such as
during an outbreak of an infectious disease . Vaccination schedules
and distribution of condoms are examples of public health
measures.
Role of science in health
Main article: Health science
Health science is the branch of science focused on health, and it
includes many subdisciplines. There are two approaches to health
science: the study and research of the human body and
health-related issues to understand how humans (and animals)
function, and the application of that knowledge to improve health
and to prevent and cure diseases .
Sources
Health research builds primarily on the basic sciences of biology ,
chemistry , and physics as well as a variety of multidisciplinary
fields (for example medical sociology ). Some of the other
primarily research-oriented fields that make exceptionally
significant contributions to health science are biochemistry ,
epidemiology , and genetics .
Application
Applied health sciences also endeavor to better understand health,
but in addition they try to directly improve it. Some of these are:
biomedical engineering , biotechnology , nursing , nutrition ,
pharmacology , pharmacy , public health ( see above ), psychology ,
physical therapy , and medicine . The provision of services to
maintain or improve people's health is referred to as health care (
see above ).
In chemistry , an alkali (from Arabic : Al-Qaly
القلي,
القالي ) is a basic , ionic
salt of an alkali metal or alkaline earth metal element . Alkalis
are best known for being bases that dissolve in water . Bases are
compounds with a pH greater than 7. The adjective alkaline is
commonly used in English as a synonym for base, especially for
soluble bases. This broad use of the term is likely to have come
about because alkalis were the first bases known to obey the
Arrhenius definition of a base and are still among the more common
bases. Since Brønsted-Lowry acid-base theory , the term
alkali in chemistry is normally restricted to those salts
containing alkali and alkaline earth metal elements.
Contents
1 Etymology
2 Common properties
3 Confusion between alkali and base
4 Salts
5 Alkaline soil
6 Lakes
7 References
//
Etymology
The word "alkali" is derived from Arabic al qalīy = the
calcined ashes , referring to the original source of alkaline
substance. Ashes were used in conjunction with animal fat to
produce soap , a process known as saponification .
Common properties
Alkalis are all Arrhenius bases, which form hydroxide ions (OH - )
when dissolved in water. Common properties of alkaline aqueous
solutions include:
Moderately-concentrated solutions (over 10 −3 M) have a pH of
7.1 or greater. This means that they will turn phenolphthalein from
colorless to pink.
Concentrated solutions are caustic (causing chemical burns).
Alkaline solutions are slippery or soapy to the touch, due to the
saponification of the fatty acids on the surface of the skin.
Alkalis are normally water soluble , although some like barium
carbonate are only soluble when reacting with an acidic aqueous
solution.
Acids and alkalis are measured on a pH scale
Alkalis are commonly found in household cleaners and toothpaste
Confusion between alkali and base
The terms "base" and "alkali" are often used interchangeably,
particularly outside of a scientific context, but they do not have
the same meaning. While all alkaline solutions are basic, not all
bases are alkaline. The following are common mistakes:
The phrase "measuring the alkalinity of soil" is incorrect since
the property measured is actually the pH (base property).
Calling bases that are not alkalis, such as ammonia , alkaline
(ammonia is a base but not an alkali).
Also, not all salts formed by alkali metals are alkaline; this
designation applies only to those salts that are basic. And while
most electropositive metal oxides are basic, only the soluble
alkali metal and alkaline earth metal oxides can be correctly
called alkalis.
This definition of an alkali as a basic salt of an alkali metal or
alkaline earth metal is the most common, based on dictionary
definitions [1] [2] , however conflicting definitions of the term
alkali do exist. These include:
Any base that is water-soluble and forms hydroxide ions [3] [4] .
In chemistry, this is more accurately called an Arrhenius base
.
The solution of a base in water [5] . This would be an Arrhenius
base in solution.
Name given by chemists to an important group of subtances, the
behaviour of bases the main alkali are 1,the hydroxides potassium
2,
Salts
Most basic salts are alkali salts, of which common examples
are:
sodium hydroxide (often called "caustic soda")
potassium hydroxide (commonly called "caustic potash")
lye (generic term, for either of the previous two, or even for a
mixture)
calcium carbonate (sometimes called "free lime")
magnesium hydroxide is an example of an atypical alkali since it
has low solubility in water (although the dissolved portion is
considered a strong base due to complete dissociation of its
ions).
Alkaline soil
Soil with a pH value higher than 7.3 is normally referred to as
alkaline. This soil property can occur naturally, due to the
presence of alkali salts. Although some plants do prefer slightly
basic soil (including vegetables like cabbage and fodder like
buffalograss ), most plants prefer a mildly acidic soil (pH between
6.0 and 6.8), and alkaline soils can cause problems.
Lakes
In alkali lakes (a type of salt lake ), evaporation concentrates
the naturally-occurring alkali salts, often forming a crust of
mildly-basic salt across a large area.
Examples of alkali lakes:
Redberry Lake, Saskatchewan , Canada .
Tramping Lake, Saskatchewan , Canada.
Mono lake , California , United States
Summer Lake , Oregon , United States
Alkali Lake, British Columbia and the adjoining reserves of the
Alkali Lake Indian Band are named for a local Alkali Lake, which
got its name from a large patch of alkali on the hillside above the
lake, which is not itself alkali, [ 1 ] although there are many in
the Cariboo district and adjoining regions of the British Columbia
Interior .
In chemistry , an alkali (from Arabic : Al-Qaly
القلي,
القالي ) is a basic , ionic
salt of an alkali metal or alkaline earth metal element . Alkalis
are best known for being bases that dissolve in water . Bases are
compounds with a pH greater than 7. The adjective alkaline is
commonly used in English as a synonym for base, especially for
soluble bases. This broad use of the term is likely to have come
about because alkalis were the first bases known to obey the
Arrhenius definition of a base and are still among the more common
bases. Since Brønsted-Lowry acid-base theory , the term
alkali in chemistry is normally restricted to those salts
containing alkali and alkaline earth metal elements.
Contents
1 Etymology
2 Common properties
3 Confusion between alkali and base
4 Salts
5 Alkaline soil
6 Lakes
7 References
//
Etymology
The word "alkali" is derived from Arabic al qalīy = the
calcined ashes , referring to the original source of alkaline
substance. Ashes were used in conjunction with animal fat to
produce soap , a process known as saponification .
Common properties
Alkalis are all Arrhenius bases, which form hydroxide ions (OH - )
when dissolved in water. Common properties of alkaline aqueous
solutions include:
Moderately-concentrated solutions (over 10 −3 M) have a pH of
7.1 or greater. This means that they will turn phenolphthalein from
colorless to pink.
Concentrated solutions are caustic (causing chemical burns).
Alkaline solutions are slippery or soapy to the touch, due to the
saponification of the fatty acids on the surface of the skin.
Alkalis are normally water soluble , although some like barium
carbonate are only soluble when reacting with an acidic aqueous
solution.
Acids and alkalis are measured on a pH scale
Alkalis are commonly found in household cleaners and toothpaste
Confusion between alkali and base
The terms "base" and "alkali" are often used interchangeably,
particularly outside of a scientific context, but they do not have
the same meaning. While all alkaline solutions are basic, not all
bases are alkaline. The following are common mistakes:
The phrase "measuring the alkalinity of soil" is incorrect since
the property measured is actually the pH (base property).
Calling bases that are not alkalis, such as ammonia , alkaline
(ammonia is a base but not an alkali).
Also, not all salts formed by alkali metals are alkaline; this
designation applies only to those salts that are basic. And while
most electropositive metal oxides are basic, only the soluble
alkali metal and alkaline earth metal oxides can be correctly
called alkalis.
This definition of an alkali as a basic salt of an alkali metal or
alkaline earth metal is the most common, based on dictionary
definitions [1] [2] , however conflicting definitions of the term
alkali do exist. These include:
Any base that is water-soluble and forms hydroxide ions [3] [4] .
In chemistry, this is more accurately called an Arrhenius base
.
The solution of a base in water [5] . This would be an Arrhenius
base in solution.
Name given by chemists to an important group of subtances, the
behaviour of bases the main alkali are 1,the hydroxides potassium
2,
Salts
Most basic salts are alkali salts, of which common examples
are:
sodium hydroxide (often called "caustic soda")
potassium hydroxide (commonly called "caustic potash")
lye (generic term, for either of the previous two, or even for a
mixture)
calcium carbonate (sometimes called "free lime")
magnesium hydroxide is an example of an atypical alkali since it
has low solubility in water (although the dissolved portion is
considered a strong base due to complete dissociation of its
ions).
Alkaline soil
Soil with a pH value higher than 7.3 is normally referred to as
alkaline. This soil property can occur naturally, due to the
presence of alkali salts. Although some plants do prefer slightly
basic soil (including vegetables like cabbage and fodder like
buffalograss ), most plants prefer a mildly acidic soil (pH between
6.0 and 6.8), and alkaline soils can cause problems.
Lakes
In alkali lakes (a type of salt lake ), evaporation concentrates
the naturally-occurring alkali salts, often forming a crust of
mildly-basic salt across a large area.
Examples of alkali lakes:
Redberry Lake, Saskatchewan , Canada .
Tramping Lake, Saskatchewan , Canada.
Mono lake , California , United States
Summer Lake , Oregon , United States
Alkali Lake, British Columbia and the adjoining reserves of the
Alkali Lake Indian Band are named for a local Alkali Lake, which
got its name from a large patch of alkali on the hillside above the
lake, which is not itself alkali, [ 1 ] although there are many in
the Cariboo district and adjoining regions of the British Columbia
Interior .
A water ionizer is an appliance that ionizes water . Ionized water
is purported to be beneficial to human health and marketed with
claims that it is an antioxidant which can slow aging and prevent
disease. [ 1 ] Others note that such claims contradict basic laws
of chemistry and physiology. [ 2 ]
Contents
1 Ionization
2 Uses
3 See also
4 References
5 External links
//
Ionization
Main article: Electrolysis of water
A water ionizer separates water into alkaline and acid fractions
using a process known as electrolysis . [ 3 ] It does this by
exploiting the electric charge of the calcium and magnesium ions
present in nearly all sources of drinking water. When a source of
water lacks mineral ions, such as distilled water , or has been
filtered by reverse osmosis , water ionization has no effect.
Uses
Some research suggests that alkaline reduced water may be useful in
scavenging free radicals in the laboratory setting. [ 4 ] Tests on
in vitro lymphocytes suggest that reduced water can prevent
hydrogen peroxide -induced damage to DNA , RNA and certain proteins
. [ 5 ] However, drinking ionized water would not be expected to
alter the body's pH , and there is no evidence of any claims made
by manufacturers that drinking ionized water will have a noticeable
effect on the body. [ 2 ]
Electrolyzed water has been used by the food industry to sanitize
food products; though effective in bacterial solutions, it was
found less useful when sanitizing utensils, surfaces and food
products. [ 6 ] [ 7 ] Acidic electrolyzed water (pH 2.3–2.6)
may have use as a seed surface disinfectant or contact bactericide
. [ 8 ]
In chemistry , an alkali (from Arabic : Al-Qaly
القلي,
القالي ) is a basic , ionic
salt of an alkali metal or alkaline earth metal element . Alkalis
are best known for being bases that dissolve in water . Bases are
compounds with a pH greater than 7. The adjective alkaline is
commonly used in English as a synonym for base, especially for
soluble bases. This broad use of the term is likely to have come
about because alkalis were the first bases known to obey the
Arrhenius definition of a base and are still among the more common
bases. Since Brønsted-Lowry acid-base theory , the term
alkali in chemistry is normally restricted to those salts
containing alkali and alkaline earth metal elements.
Contents
1 Etymology
2 Common properties
3 Confusion between alkali and base
4 Salts
5 Alkaline soil
6 Lakes
7 References
//
Etymology
The word "alkali" is derived from Arabic al qalīy = the
calcined ashes , referring to the original source of alkaline
substance. Ashes were used in conjunction with animal fat to
produce soap , a process known as saponification .
Common properties
Alkalis are all Arrhenius bases, which form hydroxide ions (OH - )
when dissolved in water. Common properties of alkaline aqueous
solutions include:
Moderately-concentrated solutions (over 10 −3 M) have a pH of
7.1 or greater. This means that they will turn phenolphthalein from
colorless to pink.
Concentrated solutions are caustic (causing chemical burns).
Alkaline solutions are slippery or soapy to the touch, due to the
saponification of the fatty acids on the surface of the skin.
Alkalis are normally water soluble , although some like barium
carbonate are only soluble when reacting with an acidic aqueous
solution.
Acids and alkalis are measured on a pH scale
Alkalis are commonly found in household cleaners and toothpaste
Confusion between alkali and base
The terms "base" and "alkali" are often used interchangeably,
particularly outside of a scientific context, but they do not have
the same meaning. While all alkaline solutions are basic, not all
bases are alkaline. The following are common mistakes:
The phrase "measuring the alkalinity of soil" is incorrect since
the property measured is actually the pH (base property).
Calling bases that are not alkalis, such as ammonia , alkaline
(ammonia is a base but not an alkali).
Also, not all salts formed by alkali metals are alkaline; this
designation applies only to those salts that are basic. And while
most electropositive metal oxides are basic, only the soluble
alkali metal and alkaline earth metal oxides can be correctly
called alkalis.
This definition of an alkali as a basic salt of an alkali metal or
alkaline earth metal is the most common, based on dictionary
definitions [1] [2] , however conflicting definitions of the term
alkali do exist. These include:
Any base that is water-soluble and forms hydroxide ions [3] [4] .
In chemistry, this is more accurately called an Arrhenius base
.
The solution of a base in water [5] . This would be an Arrhenius
base in solution.
Name given by chemists to an important group of subtances, the
behaviour of bases the main alkali are 1,the hydroxides potassium
2,
Salts
Most basic salts are alkali salts, of which common examples
are:
sodium hydroxide (often called "caustic soda")
potassium hydroxide (commonly called "caustic potash")
lye (generic term, for either of the previous two, or even for a
mixture)
calcium carbonate (sometimes called "free lime")
magnesium hydroxide is an example of an atypical alkali since it
has low solubility in water (although the dissolved portion is
considered a strong base due to complete dissociation of its
ions).
Alkaline soil
Soil with a pH value higher than 7.3 is normally referred to as
alkaline. This soil property can occur naturally, due to the
presence of alkali salts. Although some plants do prefer slightly
basic soil (including vegetables like cabbage and fodder like
buffalograss ), most plants prefer a mildly acidic soil (pH between
6.0 and 6.8), and alkaline soils can cause problems.
Lakes
In alkali lakes (a type of salt lake ), evaporation concentrates
the naturally-occurring alkali salts, often forming a crust of
mildly-basic salt across a large area.
Examples of alkali lakes:
Redberry Lake, Saskatchewan , Canada .
Tramping Lake, Saskatchewan , Canada.
Mono lake , California , United States
Summer Lake , Oregon , United States
Alkali Lake, British Columbia and the adjoining reserves of the
Alkali Lake Indian Band are named for a local Alkali Lake, which
got its name from a large patch of alkali on the hillside above the
lake, which is not itself alkali, [ 1 ] although there are many in
the Cariboo district and adjoining regions of the British Columbia
Interior .
A water ionizer is an appliance that ionizes water . Ionized water
is purported to be beneficial to human health and marketed with
claims that it is an antioxidant which can slow aging and prevent
disease. [ 1 ] Others note that such claims contradict basic