Animals as a medical resource Category: Plant and animal resources The use of animals has been a critical component of both human medical research and veterinary research.. Although anim
Trang 1in Industrial America Cambridge, Mass.: Harvard
University Press, 2008
Kalof, Linda, and Brigitte Resl, eds A Cultural History
of Animals 6 vols New York: Berg, 2007.
Pynn, Larry “Logging with Horse Power.” Canadian
Geographic 111, no 4 (August/September, 1991):
30
Schmidt, Michael J., and Richard Ross “Working
Ele-phants: They Earn Their Keep in Asia by Providing
an Ecologically Benign Way to Harvest Forests.”
Sci-entific American 274, no 1 (January, 1996): 82.
Tiwari, G N., and M K Ghosal “Draught Animal
Power.” In Renewable Energy Resources: Basic
Princi-ples and Applications Harrow, England: Alpha
Sci-ence International, 2005
Watts, Martin Working Oxen Princes Risborough,
En-gland: Shire, 1999
See also: Animal breeding; Animal domestication;
Livestock and animal husbandry; Transportation,
en-ergy use in
Animals as a medical resource
Category: Plant and animal resources
The use of animals has been a critical component of
both human medical research and veterinary research.
Although animal research has become a source of
con-troversy among the public, nearly all modern medical
advances have been based on some form of animal
re-search.
Background
Animals have served purposes related to medicine for
centuries They provided medical products for
apoth-ecaries in medieval Europe and for traditional
Chi-nese medicine Most applications, such as the use
of ground rhinoceros horn as an aphrodisiac, were
based on nonscientific concepts that have been
dis-carded by modern medicine However, some
tech-niques, such as the use of spiderweb to stop bleeding,
functioned until more effective products became
available
More recently, insulin used to treat diabetes was
first harvested from the pancreatic glands of cattle or
pigs used in the meat industry; however, the foreign
animal proteins sometimes caused allergic reactions
Today, genetically engineered bacteria can provide many hormone products that previously were ex-tracted from animals Animals have also provided transplant organs Tissue rejection has been a major problem, but medications can reduce rejection dra-matically
Through genetic engineering, genes that code for pharmaceutical proteins can be incorporated into an-imals, and medicinal drugs can then be produced from the animal’s milk Clinical trials are under way for animal production of anti-blood-clotting agents Transgenic animals have also been proposed for the production of drugs to treat cystic fibrosis, cancer, and other disorders The uses of animals for products and tissues, however, have been minor compared with the use of animals as test subjects in medical research Animal Medical Research
Phenomenal advances in the treatment of human dis-eases occurred in the century following the Civil War The development of germ theory by Louis Pasteur and Robert Koch, as well as the conquest of most ma-jor infectious diseases, was based on extensive animal research Pasteur’s studies of chicken cholera formed
a basis for his work, and Koch’s breakthrough work with anthrax involved studies with sheep Most Nobel Prizes in Physiology or Medicine (first awarded in 1901) have involved some form of animal research The first half of the twentieth century was an era of widespread public support for medical and scientific research Animal research underlay basic studies in the development of penicillin and other major antibi-otics as well as insulin, surgical techniques, and vacci-nations Partly because people had recent memories
of the severity of such major diseases as smallpox and polio, animal research engendered little protest or controversy
Not all animals are equally useful or appropriate in medical research, because some have systems that dif-fer significantly from human physiology The closer
an animal is to humans evolutionarily, the more likely
it is that it will respond to drugs and medical interven-tions in the same manner that humans will Most new drugs are first screened on laboratory rats or mice; those drugs that show promise and have no toxic ef-fects may then be tested on primates Approximately
95 percent of medical research uses mice and other rodents, and nearly all the mice and rats used are
“purpose bred” for research (Cats, dogs, and nonhu-man primates make up less than 1 percent of animals
Trang 2used in research.) The protocols for Federal Drug
Administration approval of new drugs, as well as
agri-cultural and environmental standards, are based on
substantial animal testing to ensure the safety and
effectiveness of new medications
Opposition and Controversy
Beginning in the late 1970’s, opposition to animal
re-search began to gain national attention The books
Animal Liberation, by Peter Singer (1977), and The Case
for Animal Rights, by Tom Regan (1983), provided a
rationale to activists who questioned humans’ use of
other animals for medical research as well as for food,
fur, and educational uses Organizations opposed to
some or all animal use in research range from radical
groups allegedly responsible for vandalism of research
laboratories (the Animal Liberation Front is among
the most radical groups) to milder animal
protection-ist organizations Probably the best-known
animal-rights group is People for the Ethical Treatment of
Animals (PETA) Well-known defenders of animal re-search for medical science include the National Asso-ciation for Biomedical Research (NABR), the Incurably Ill for Animal Research, and Putting People First
Some anti-animal-research activists have con-tended that all animal research can be replaced with alternatives such as research involving tissue culture and computer simulation Activists also object to the use of animals taken from animal shelters and com-plain that current animal care regulations, particu-larly under the Animal Welfare Act, are not rigorously enforced by the U.S Department of Agriculture The scientific community has defended animal re-search for a number of reasons Biological systems are much more complex than any computer model de-vised, so at present computer simulation has severe limitations New drugs rarely respond in tissue culture exactly as they do in a whole living organism Re-searchers point out that, although animals are taken from shelters for research use, they constitute a mi-nuscule amount of the dogs and cats that are eutha-nized annually By far, most of the animals used in research and teaching are mice and rats Research fa-cilities are inspected by agencies such as the United States Department of Agriculture’s Animal and Plant Health Inspection Service, which enforces Animal Welfare Act criteria The Food and Drug Administra-tion and the Environmental ProtecAdministra-tion Agency also have laboratory practice regulations The research community also states that approximately 95 per-cent of laboratory animals are never subjected to pain and that the remaining animals are provided pain-relieving drugs or anesthetics as soon as the study permits
John Richard Schrock
Further Reading
Birke, Lynda, Arnold Arluke, and Mike Michael The Sacrifice: How Scientific Experiments Transform Ani-mals and People West Lafayette, Ind.: Purdue
Uni-versity Press, 2007
Carbone, Larry What Animals Want: Expertise and Ad-vocacy in Laboratory Animal Welfare Policy New York:
Oxford University Press, 2004
Haugen, David M., ed Animal Experimentation
De-troit: Greenhaven Press, 2007
Monamy, Vaughan Animal Experimentation: A Guide to the Issues 2d ed New York: Cambridge University
Press, 2009
This mouse was genetically engineered by researchers at the
Univer-sity of California, Davis, to use in the study of breast cancer (AP/
Wide World Photos)
Trang 3National Research Council of the National
Acad-emies Science, Medicine, and Animals: A Circle of
Dis-covery Washington, D.C.: National Research
Coun-cil, National Academies Press, 2004
Paul, Ellen Frankel, and Jeffrey Paul, eds Why Animal
Experimentation Matters: The Use of Animals in Medical
Research Edison, N.J.: Transaction, 2001.
Regan, Tom The Case for Animal Rights 1983 Reprint.
Berkeley: University of California Press, 2004
Rudacille, Deborah The Scalpel and the Butterfly: The
Conflict Between Animal Research and Animal
Protec-tion Berkeley: University of California Press, 2001.
Singer, Peter Animal Liberation 2d ed New York: New
York Review of Books, 1990
Verhetsel, Ernest They Threaten Your Health: A Critique
of the Antivivisection/Animal Rights Movement
Tuc-son, Ariz.: People for Ethical Animal Research,
1986
Web Sites
Humane Society of the United States
Animal Testing
http://www.hsus.org/animals_in_research/
animal_testing
National Academies Press
Science, Medicine, and Animals
http://www.nap.edu/
catalog.php?record_id=10733#toc
U.S Food and Drug Administration
Animal Testing
http://www.cfsan.fda.gov/~dms/cos-205.html
See also: Animal breeding; Animal domestication;
Biotechnology; Livestock and animal husbandry;
Plants as a medical resource; Wildlife
Antarctic treaties
Category: Laws and conventions
Date: Final draft presented on December 1, 1959;
became effective on June 23, 1961
The Antarctic Treaty of 1959, created and endorsed by
representatives of the twelve signatory nations and
en-dorsed by many other nations since, designates
Antarc-tica as a demilitarized zone and bans commercial
min-eral and oil exploration there until 2041, when the
treaty’s provisions will be reviewed and possibly al-tered It also bans the disposal of radioactive waste in the area.
Background Exploration of Antarctica began early in the twentieth century when sailors hunting whales and seals pene-trated the waters surrounding this forbidding conti-nent As early as 1940, seven countries—Argentina, Australia, Chile, France, New Zealand, Norway, and the United Kingdom—had laid claim to various parts
of Antarctica Some such claims overlapped, increas-ing the potential for conflict
Antarctica is unique among Earth’s seven conti-nents because it has no permanent residents and no established government Its harsh climate makes it more suitable for scientists than for soldiers and en-trepreneurs During the International Geophysical Year (IGY), which ran from July 1, 1957, until Decem-ber 31, 1958, twelve nations built thirty-five scientific research stations on the continent and fifteen on the nearby Antarctic islands As of 2009, there were sixty-five research stations in Antarctica, many of which op-erated only during the Antarctic summer, which runs from mid-October until early March
When the IGY ended, representatives from the twelve nations involved in that project gathered in Washington, D.C., and produced the Antarctic Treaty, whose sixteen articles spelled out how the continent would be devoted to scientific research Representa-tives of the twelve signatory nations presented the treaty on December 1, 1959 It went into effect on June 23, 1961
Among other documents that compose the Antarc-tic Treaty System are the Conservation of AntarcAntarc-tic Fauna and Flora, the Convention for the Conserva-tion of Antarctic Seals, and the ConvenConserva-tion on the Conservation of Antarctic Marine Living Resources The Antarctic Treaty was expanded in 1991, when twenty-four countries signed the Madrid Protocol, which banned commercial development, mining, and exploration for oil on the continent for fifty years This provision will be reconsidered in 2041
By 2010, forty-five nations, representing more than
80 percent of the world’s population, had endorsed the Antarctic treaties, which are the most effective such international treaties ever entered into by such a broad spectrum of nations Antarctica remains the most peaceful of Earth’s seven continents, with repre-sentatives of nearly one hundred nations working
Trang 4operatively on their scientific pursuits and sharing
their findings with their fellow scientists
Provisions
The provisions of the Antarctic treaties were not
ac-cepted merely on the basis of a majority vote They
were, instead, passed by consensus, which explains, at
least partially, their overwhelming success and broad
acceptance
As the IGY neared its termination in 1958,
consid-erable concern existed that the seven nations that had
laid claim to parts of Antarctica would begin to have
disputes about their claims It was these concerns that
led the U.S State Department to inaugurate meetings
in Washington, D.C., with eleven other nations that
had vested interests in Antarctica
Representatives of these nations met for more than
a year in an attempt to reach an accord that would
protect Antarctica from widespread incursions from a
host of nations Through these meetings the
Antarc-tic Treaty was forged It was signed on December 1,
1959, by representatives of the twelve nations that
par-ticipated in the IGY, after which it was ratified and
went into effect on June 23, 1961
Perhaps the most important provision of the treaty
is its stipulation that all of the signatories agree to
abandon all territorial claims on this frozen
conti-nent This provision alleviated the fear that the seven
nations that had previously laid claim to parts of
Ant-arctica, all of which were involved in drafting the
treaty, would exercise what they considered their
pro-prietary rights and could conceivably enter into
dan-gerous conflicts to protect such rights
Once this caveat was overcome, the rest of the
pro-visions of the treaty fell into place Cognizant of the
importance of keeping Antarctica a peaceful
conti-nent, the initial Antarctic Treaty banned all military
activity on the continent It also forbade the testing of
weapons, nuclear testing, and the disposal of nuclear
waste on the continent These provisions set aside 10
percent of the Earth’s surface as nuclear-free and
de-militarized zones
Among the protective stipulations of the Antarctic
Treaty produced in 1959 is the prohibition of the
im-portation of soil into the continent The fear is that
imported soil will carry with it unknown biohazards
such as fungi, bacteria, and insects that might pollute
the pristine atmosphere of Antarctica
Openness is a major theme of the treaty’s
provi-sions, which call for the free exchange of scientific
in-formation among the disparate groups of scientists who are involved in polar research Scientists from the signatory nations covered by the treaty are expected
to share information with one another and to make their research plans and scientific outcomes avail-able The provisions of the treaty permit personnel from any of the research stations to visit and inspect without prior notice any of the research facilities in Antarctica
Realizing that disputes arise inevitably in multina-tional situations, those who drafted the treaty pro-vided for conflict resolution Efforts must be made to settle disputes through arbitration or negotiation If such efforts fail, however, the problem is referred to the International Court of Justice for a resolution that
is considered binding Those who drafted the treaty were conscious of the need to make it sufficiently flex-ible to deal with new issues or problems as they arise in rapidly changing contexts
The official languages of the treaty are English, French, Russian, and Spanish The documents associ-ated with the treaty are held by the government of the United States, which is responsible for preserving them and distributing them as required
There are two levels of membership in the Antarc-tic Treaty System, consultative and nonconsultative
In order to be consultative members, nations must maintain at least one research station in Antarctica Consultative members have voting rights that are not available to nonconsultative members In some in-stances, consultative members close their research stations, as India did its Dakshin Gangotri Station in
1981, but as long as they maintain one station—India continues to maintain the Maitre Station as a perma-nent facility—they retain consultative membership Since the enactment of the treaty, society has be-come increasingly sensitive to environmental prob-lems that received less attention in the 1960’s than they did in the 1990’s and beyond As a result of this change in outlook, the Madrid Protocol was enacted
in 1991 It bans exploration for oil and other minerals
in Antarctica for fifty years In 2041, this provision will
be revisited and possibly reconsidered
Impact on Resource Use Antarctica is a mineral-rich continent, but its harsh climate and the thick ice sheets—some more than 3 kilometers deep—that cover it make the retrieval of minerals expensive and hazardous Many parts of the continent never reach temperatures above freezing,
Trang 5and even those areas, such as the Antarctic Peninsula,
that have more moderate climates are too cold to
sus-tain much plant and animal life Nevertheless, as
min-ing equipment becomes increasmin-ingly sophisticated,
the recovery of oil and other minerals from Antarctica
will undoubtedly become feasible
The enactment of the Antarctic Treaty System has
been aimed at the preservation of a frozen wilderness
that has considerable potential as a source of natural
resources, although this potential remains
underde-veloped Among the other natural resources of which
the continent boasts are stores of fresh water,
esti-mated to constitute 80 percent of the fresh water on
Earth As water shortages become commonplace in
many parts of the developed world, means will be
ex-plored for transporting some of Antarctica’s
abun-dant water to water-starved regions
Some Middle Eastern countries have already
ex-plored the possibility of hauling huge icebergs into
ar-eas that are parched and of using the fresh water in
them for irrigation and other purposes, including
drinking water Most of the ice in icebergs is
com-posed of fresh water Future additions to the
Antarc-tica Treaties will likely deal with the preservation and
transportation of huge masses of ice into the
popu-lated parts of the world that are much in need of
water At the same time, future amendments may
need to address the consequences of global climate
change as well
R Baird Shuman
Further Reading
Bocknek, Jonathan Antarctica: The Last Wilderness.
North Mankato, Minn.: Smart Apple Media, 2004
Currie, Stephen Antarctica New York: Lucent Books,
2004
Karner, Julie Roald Amundsen: The Conquest of the South
Pole New York: Crabtree, 2007.
Myers, Walter Dean Antarctica: Journeys to the South
Pole New York: Scholastic Press, 2004.
Rubin, Jeff Antarctica 4th ed London: Lonely Planet,
2008
Shackleton, Ernest The Heart of the Antarctic: Being the
Story of the British Antarctic Expedition, 1907-1909.
New ed London: Carroll and Graff, 1999
Stonehouse, Bernard North Pole, South Pole: A Guide to
the Ecology and Resources of the Arctic and Antarctic.
London: Prion, 1990
See also: Climate and resources; Oil and natural gas distribution; Oil and natural gas exploration; Ozone layer and ozone hole debate; Population growth; Re-sources as a source of international conflict
Antimony
Category: Mineral and other nonliving resources Where Found
While antimony does not often occur free in nature, its ores are widely distributed The antimony ore of greatest commercial importance is stibnite (Sb2S3), most of which is supplied by China, Germany, Peru, and Japan, among other countries
Primary Uses Antimony is a strategic resource with many uses It is a key component in many alloys, and its compounds are employed in the manufacture of such products as ceramics and glass, batteries, paints and pigments, chemicals, matches, explosives, fireworks, flame retar-dants, and medicines
Technical Definition Antimony (abbreviated Sb), atomic number 51, is a metalloid belonging to Group VA of the periodic ta-ble of the elements It has two naturally occurring iso-topes and an average molecular weight of 121.75 Pure antimony has rhombohedral crystals and is sil-very blue-white in color It is brittle, can be easily pow-dered, and conducts heat and electricity poorly Its specific gravity is 6.69 at 20° Celsius; its melting point
is 630.5° Celsius, and its boiling point is 1,380° Celsius Description, Distribution, and Forms
Antimony is a metalloid with a lithospheric concen-tration of 0.2 gram per metric ton When used in met-allurgical combinations antimony forms hard, brittle materials that melt at relatively low temperatures, characteristics that make this element an important component in many alloys
The most economically important antimony ore is antimony sulfide, or stibnite In the United States the element is usually obtained only as a by-product of smelting the copper ore tetrahedrite, (Cu, Fe)12Sb4S13,
or other sulfide ores of base metals While recycling scrap metal and storage batteries was once a signifi-cant secondary source of antimony for the United
Trang 6States, the development of low-maintenance
lead-acid automobile batteries that use lead alloys with less
or no antimony has decreased this supply In 2007, for
example, the United States consumed 9,590 metric
tons of antimony, and total world production was
esti-mated at 170,000 metric tons
Antimony ores are widely distributed; China,
Bo-livia, South Africa, Russia, Tajikistan, and Australia
are the chief producers China is believed to have the
world’s greatest reserves of the element; extensive
de-posits of stibnite are found in the southern province
of Hunan Antimony-bearing rocks can be found in
soils, groundwater, and surface waters Most antimony
deposits are associated with igneous activity and are
believed to have been precipitated from watery fluids
at relatively shallow depths and low temperatures
Antimony is rarely found free in nature Stibnite,
the predominant antimony ore, is a silvery gray sulfide
mineral that occurs in masses or prismatic crystals
Frequently it is found in association with quartz and
economic minerals such as ores of mercury, tungsten,
tin, lead, copper, silver, and gold Stibnite deposits are
often in the form of veins, seams, pockets, or lenses
Antimony can enter groundwater and surface water
through the natural weathering of rock or through
in-dustrial pollution It can cause disorders of the
hu-man respiratory and cardiovascular systems, skin, and
eyes, and it is a suspected cancer-causing agent The
1974 Safe Drinking Water Act set the maximum
allow-able concentration for total antimony in drinking
water in the United States at 6 micrograms per liter
History
Antimony has been used since biblical times as an
in-gredient in medicines and in kohl, an eye cosmetic
made up of powdered stibnite mixed with soot and
other materials In Tello, Chaldea, a vase from
ap-proximately 4000 b.c.e was found that had been cast
in elemental antimony; antimony was also reportedly
used by the early Egyptians to coat copper items By
the sixteenth century, the element was recognized as
an alloy ingredient that could improve the tone of bell
metal; as a source of yellow pigment for painting
earthenware, enamels, and glass; and as an ulcer
med-icine The earliest known description of the
extrac-tion of antimony from stibnite was written by Basilius
Valentinus around 1600 The increasing
industrializa-tion of the late nineteenth and early twentieth
centu-ries was accompanied by a rapid rise in antimony
consumption The need for ammunition, arms, and
flame-retardant items during World Wars I and II further increased the demand for antimony In the 1930’s, consumption of the element also rose with the expansion of the automobile industry, which used lead-antimony alloys in storage batteries
Obtaining Antimony Antimony ore is roasted with iron in a blast furnace; the roasting produces antimony oxide, from which the iron removes the oxygen to free the antimony A flux of sodium sulfate or sodium carbonate may be used to prevent the loss of molten antimony through evaporation Complex ores, those with base metals present, are treated by leaching and electrolysis Uses of Antimony
Antimony is an important element in many alloys Bri-tannia metal, an alloy of tin with antimony, copper, and sometimes bismuth and zinc, resembles pewter in appearance and is used in the manufacture of table-ware Antimony is sometimes added to pewter, an al-loy composed largely of tin, to increase whiteness and hardness Babbitt metal, an antifriction alloy used in bearings, is composed chiefly of tin, copper, and anti-mony Type metal, named for its use in the
Commodity Summaries, 2009
Data from the U.S Geological Survey,
U.S Government Printing Office, 2009.
Flame retardants 40%
Transportation
& batteries 22%
Chemicals 14%
Ceramics
& glass 11%
Other 13%
U.S End Uses of Antimony
Trang 7ture of printing type, is an alloy of lead with antimony,
tin, and sometimes copper; this alloy is also used in
metal parts for some musical instruments Various
al-loys of antimony and lead are used in solder,
starting-lighting-ignition batteries (particularly plates,
termi-nals, and connectors), ammunition, communication
equipment, corrosion-resistant pumps and pipes, tank
linings, and roofing sheets
Antimony is used as a decolorizing and refining
agent in television screens, fluorescent tubes, and
op-tical glass Small amounts of the element are used in
some medicines Antimony oxides serve as stabilizers
and flame retardants in plastics They are also used to
make adhesives, rubber, textiles, paints, and other
combustibles flame resistant Antimony sulfides are
employed as a component of fireworks and
ammuni-tion Antimony compounds are used in the
manufac-ture of matches, explosives, vulcanized rubber, paints
and pigments, chemicals, semiconductors, batteries,
glass, and ceramics Its military applications make
an-timony a strategic mineral
Karen N Kähler
Further Reading
Greenwood, N N., and A Earnshaw “Arsenic,
Anti-mony, and Bismuth.” In Chemistry of the Elements 2d
ed Boston: Butterworth-Heinemann, 1997
Henderson, William “The Group 15 (Pnictogen)
Ele-ments: Nitrogen, Phosphorus, Arsenic, Antimony,
and Bismuth.” In Main Group Chemistry
Cam-bridge, England: Royal Society of Chemistry, 2000
Krebs, Robert E The History and Use of Our Earth’s
Chemical Elements: A Reference Guide Illustrations by
Rae Déjur 2d ed Westport, Conn.: Greenwood
Press, 2006
Massey, A G “Group 15: The Pnictides—Nitrogen,
Phosphorus, Arsenic, Antimony, and Bismuth.” In
Main Group Chemistry 2d ed New York: Wiley, 2000.
Web Sites
Natural Resources Canada
Canadian Minerals Yearbook, Mineral and Metal
Commodity Reviews
http://www.nrcan-rncan.gc.ca/mms-smm/busi-indu/cmy-amc/com-eng.htm
U.S Geological Survey
Antimony: Statistics and Information
http://minerals.usgs.gov/minerals/pubs/
commodity/antimony
See also: Alloys; China; Germany; Hydrothermal solutions and mineralization; Japan; Metals and met-allurgy; Peru; Russia; South Africa; Strategic re-sources
Antiquities Act
Categories: Laws and conventions; government and resources
Date: Signed into law June 8, 1906
By designating sites of historic importance for special protection and preservation, the Act for the Preserva-tion of American Antiquities, commonly known as the Antiquities Act, pioneered the use of government power
to defend both the environmental and cultural re-sources of nations.
Background
As the population and economy of the United States expanded throughout the late nineteenth and early twentieth centuries, various groups became concerned about the survival of important elements of American culture and environment Expanding urban centers threatened wilderness areas, unrestrained tourism damaged natural wonders, and archaeological sites were vulnerable to unregulated pillaging
The destruction of American Indian archaeologi-cal sites by commercial relic hunters was a particular concern, as archaeologists feared the loss or destruc-tion of vital cultural artifacts Their concerns reached the desk of Iowa congressman John F Lacy, chairman
of the House Committee on Public Lands (later the Committee on Natural Resources) Concerned about protecting properties in the public interest, Lacy in-troduced the Antiquities Act as a means of preserving properties of national importance even if the proper-ties were in private hands The act passed easily through Congress, and became law when signed by pro-conservation president Theodore Roosevelt The Antiquities Act represented a move toward greater federal responsibility for preservation Recog-nizing that state and local governments lacked either the will or the authority to protect sites of importance
to the national heritage, the U.S federal government used its power of eminent domain to place sites under government care This marked a major philosophical shift away from government indifference to
Trang 8mental issues and toward federal participation in
preservation efforts
Provisions
The Antiquities Act authorized the president of the
United States to designate an area of historic,
cul-tural, or environmental importance a “national
mon-ument” under the ownership and stewardship of the
federal government, specifically the Department of
the Interior If the federal government did not already
own the property, the president could use the power
of eminent domain to acquire private property The
act provided for the “proper care and management”
of the site to ensure its preservation but did allow
ar-chaeological excavation by qualified researchers
un-der the supervision of the government In an attempt
to curb the pillaging of artifacts, the unauthorized
re-moval of historical artifacts became a federal offense
Impact on Resource Use
Although intended to protect archaeological sites,
the Antiquities Act also ensured the survival of a
num-ber of environmentally important areas President
Roosevelt took a broad interpretation of the
legisla-tion and designated a wide range of sites for
protec-tion Roosevelt designated Devils Tower in Wyoming
as the first national monument, followed by a number
of American Indian sites in the Southwest Since 1906,
the government has created more than one hundred
monuments in both rural areas, such as Muir Woods
in California, and urban areas, such as the Statue of
Liberty in New York Between 2006 and 2008,
Presi-dent George W Bush created the first underwater
monuments when he designated the
Papah3naumo-ku3kea Marine National Monument near Hawaii,
Marianas Trench Marine in the central Pacific, and
the Pacific Remote Islands and Rose Atoll Marines in
the U.S.-owned islands of the South Pacific
Steven J Ramold
See also: National Park Service; National Parks Act,
Canadian; National parks and nature reserves;
Re-source Conservation and Recovery Act; Takings law
and eminent domain
Appliances See Buildings and
appliances, energy-efficient
Aquifers
Category: Geological processes and formations
An aquifer is a body of earth material that can store and transmit economically significant amounts of water The earth material can be in either consolidated
or unconsolidated form as long as it has sufficient permeability for the movement of water In terms of groundwater occurrence, all the rocks found on and below the Earth’s surface are associated with either aquifers or confining beds.
Background
An aquifer is a rock unit that is permeable enough to yield water in usable amounts to a well or a spring In geologic usage, the term “rock” includes unconsoli-dated sediments such as sand, silt, and clay, as well as what is commonly considered to be rock A confining bed is a rock unit that has such low hydraulic conduc-tivity (poor permeability) that it restricts or severely impedes the flow of groundwater into or out of nearby aquifers
Unconfined and Artesian Aquifers There are two major types of groundwater occurrence
in aquifers The first type pertains to those aquifers that are only partially filled with water In those cases, the upper surface (or water table) of the saturated zone can rise or decline in response to variations in precipitation, evaporation, and pumping from wells The water in these aquifers is classified as unconfined, and such aquifers are called unconfined, or water-table, aquifers
The second type occurs when water completely fills
an aquifer that is overlain by a confining bed In this case, the water in such an aquifer is classified as con-fined and the aquifers are called concon-fined, or arte-sian, aquifers In some fractured rock formations, such as those that occur in the west-central portions of New Jersey and eastern Pennsylvania, local geologic conditions result in semiconfined aquifers that, as one might expect, have hydrogeologic characteristics
of both unconfined and confined aquifers
Wells that are drilled in unconfined, water-table aquifers are simply called water-table wells The water level in these unconfined wells indicates the depth be-low the surface of the water table, which is the top of the saturated zone Wells that are drilled into
Trang 9fined aquifers are called artesian wells The water level
in an artesian well is generally located at a height
above the top of the confined aquifer but not
neces-sarily above the land surface Flowing artesian wells
occur when the water level in an artesian well stands
above the land surface The water level in tightly cased
wells in unconfined or artesian aquifers is called the potentiometric surface of the aquifer
Aquifer Permeability Water flows (very slowly) in aquifers from recharge ar-eas in interstream arar-eas at higher elevations to
Source: Basic Ground-Water Hydrology
Note:
Ralph C Heath, , U.S Geological Survey Water-Supply Paper 2220, 1983.
Rocks vary tremendously in their ability to conduct water The meters-per-day scale is logarithmic: Each increment to the right and left of 1 indicates a change by a power of 10: to the right, 10 meters, 1,000 meters, and 100,000 meters; to the left, 0.1 meter, 0.01 meter, 0.001 meter, and so on.
10–7 10–6 10–5 10–4 10–3 10–2 10–1 1 10 102 103 104
10–8
Meters per Day
GRAVEL GLACIAL TILL
CLEAN SAND
SILTY SAND
SILT, LOESS CLAY
CARBONATE ROCKS
SHALE
SANDSTONE
Fractured Semiconsolidated
BASALT
IGNEOUS AND METAMORPHIC ROCKS
10–7 10–6 10–5 10–4 10–3 10–2 10–1 1 10 102 103 104
10–8
Meters per Day
Hydraulic Conductivity of Select Rocks and Materials
Trang 10charge areas along streams and adjacent floodplains
at lower elevations Thus, aquifers function as
“pipe-lines” filled with various types of earth material
Darcy’s law governing groundwater flow was
devel-oped by Henry Darcy, a French engineer, in 1856 In
brief, Darcy’s law states that the amount of water
mov-ing through an aquifer per unit of time is dependent
on the hydraulic conductivity (or permeability) of the
aquifer, the cross-sectional area that is at a right angle
to the direction of flow, and the hydraulic gradient
The hydraulic conductivity depends upon the size
and interconnectedness of the pores and fractures in
an aquifer It ranges through an astonishing twelve
or-ders of magnitude There are few other physical
pa-rameters that have such a wide range of values For
ex-ample, the hydraulic conductivity ranges from an
extremely low 10−7 and 10−8 meters per day in
unfractured igneous rock such as diabase and basalt
to as much as 103and 104meters per day in cavernous
limestone and coarse gravel Typical low-permeability
earth materials include unfractured shale, clay, and
glacial till High-permeability earth materials include
lava flows and coarse sand
In addition to this wide range of values, hydraulic
conductivity varies widely in place and in
direction-ality within the same aquifer Aquifers are isotropic if
the hydraulic conductivity is about the same in all
di-rections, and anisotropic if it is different in different
directions As a result of all of these factors,
groundwa-ter yield is extremely variable both within the same
aquifer and from one aquifer to another when they
are composed of different rocks
Aquifer Tests
In order to determine the groundwater yield and
contaminant transport characteristics of an aquifer,
it is necessary to obtain sufficient geologic and
hy-drologic information One of the most important
hydrologic investigations in such a study is the analysis
of the change over time of the water levels in an
aqui-fer as a consequence of well pumpage This type of
study is called an aquifer test and usually involves
pumping a well at a constant rate for several hours to
several days while changes in the water levels of one or
more observation wells located at different distances
from the pumped well are measured The test
pro-vides invaluable information about the ability of an
aquifer to yield sufficient water under the stress of
constant pumping
Robert M Hordon
Further Reading
Appelo, C A J., and D Postma Geochemistry, Ground-water, and Pollution 2d ed New York: Balkema,
2005
Fetter, C W Applied Hydrogeology 4th ed Upper
Sad-dle River, N.J.: Prentice Hall, 2001
Price, Michael Introducing Groundwater 2d ed New
York: Chapman & Hall, 1996
Todd, David Keith, and Larry W Mays Groundwater Hydrology 3d ed Hoboken, N.J.: Wiley, 2005 Younger, Paul L Groundwater in the Environment: An In-troduction Malden, Mass.: Blackwell, 2007.
Zektser, Igor S., and Lorne G Everett, eds Ground Water Resources of the World and Their Use Paris:
UNESCO, 2004 Reprint Westerville, Ohio: Na-tional Ground Water Association Press, 2006 Web Sites
Natural Resources Canada Groundwater
http://atlas.nrcan.gc.ca/site/english/maps/ freshwater/distribution/groundwater/1 U.S Geological Survey
Aquifer Basics http://water.usgs.gov/ogw/aquiferbasics See also: Environmental engineering; Glaciation; Groundwater; Hydrology and the hydrologic cycle; Land-use planning; U.S Geological Survey; Water pollution and water pollution control; Water supply systems
Argentina
Categories: Countries; government and resources
Argentina’s greatest primary natural resource is its ag-ricultural land Owing to its size, Argentina has a va-riety of climates and soils in which to grow crops and raise livestock As a result, the country is a top-ten ex-porter of a variety of crop and meat products More-over, a complex geology endows Argentina with depos-its of petroleum, natural gas, copper, gold, and other minerals that make the country a significant exporter
of these materials to its neighbors and other countries around the globe.