Có 60+ tài liệu thuộc chủ đề "nghiên cứu môi trường"
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their forests, their consumption patterns have led to the continuing deforestation of the tropics.. Clearing of forests without suitable replanting de- creases timber supplies, often leads to potential deg- radation of the soil and water, reduces species diver- sity, and may contribute to long-term climatic change.. Because of reforestation projects, forest cover in the United States and Western Europe began...
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290 • Department of Energy, U.S. Department of Energy. Office of the Under Secretary For Nuclear Security/. Office of the Under Secretary. After the end of the Cold War in 1990, the Depart- ment of Energy deemphasized production of new nuclear weapons and shifted some support to theoret- ical research: particle acceleration experiments at the Department of Energy’s Fermi National...
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In the United States, cool deserts (sagebrush grass and salt-desert shrub types) occur in old lake beds.. Some plants, such as mesquite, have deep root systems that allow access to deep sources of water.. Some plants have dense, shallow root sys- tems that allow them to tap soil water in the soil sur- face from light showers. Some plants, such...
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Diatomite is a soft, chalklike, fine-grained sedimen- tary rock composed primarily of the fossilized silica shells of microscopic algae called diatoms. The word “diatom” comes from Greek diatomos, meaning “cut in half,” because of the two valves.. Three main types of diatomite deposits are recognized in the United States: marine rocks near continental margins, lacustrine rocks formed in ancient lakes...
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drought occurred in the region during the 1950’s, the mid-1970’s, and the late 1980’s. Until the mid-1800’s the only explosive available was black powder, which was lacking in power and created flames that constituted a fire or dust explosion hazard in mines. Although it did find use in the mining industry, the hazard of pre- mature explosions was extreme, and...
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Until the 1960’s, forestry, fish, and wildlife management techniques were aimed at increasing the productivity of single species—usually game species, such as quail and trout, or commercial tree species, such as loblolly pine. As community ecology and ecosystem ecology matured, and as popular concern for the loss of species arose in the 1960’s, natural resource management agen- cies began to...
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31 million square kilometers, which is nearly 21 per- cent of the entire world landmass. The tropics with summer rain zone constitutes, ap- proximately, bands of moist and dry savannas north and south of the equator, 25 million square kilome- ters, in northern and eastern South America, central and southern Africa, India, Southeast Asia, and north- ern Australia and nearby...
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An example of such a seed bank in the United States is the National Plant Germplasm System in Colorado, under the aegis of the Department of Agriculture.. Endangered Species and Medicine. Even though researchers, especially those active during and since the chemical revolution of the eighteenth century, have developed a growing number of artificial drugs that have proved increasingly effective...
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Geologist Marion King Hubbert noted a bell-shaped curve in the use of resources, now commonly called the “Hubbert curve” and often used in estimates of resource use and reserves. (Hubbert first applied his curve to petroleum in the late 1940’s and subse- quently reviewed and amended his prediction a num- ber of times.) According to the Hubbert curve, a re-...
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Several such systems are in operation in the United States. In spite of the technical and economic viability of pumped hydro, the require- ment of a specific type of topography and some envi- ronmental concerns limit its application. Solar Heat Storage. When converted into heat, solar energy can be stored in the form of sensible heat and latent heat. The...
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Meter, cubic Volume/capacity m 3 1.308 cubic yards. Microgram Mass/weight mcg or µg 0.000001 gram. Microliter Volume/capacity µl 0.00027 fluid ounce. Milligram Mass/weight mg 0.015 grain. Milliliter Volume/capacity ml 0.271 fluid dram. Mass/weight oz 28.350 grams. Mass/weight oz 31.103 grams. Mass/weight oz 1.805 cubic inch. Peck Volume/capacity pk 8.810 liters. Volume/capacity pt 33.600 cubic inches. Volume/capacity pt 28.875 cubic inches....
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Global Resources. Environment and Natural Resources Division. The Environment and Natural Resources Division of the U.S. Department of Justice litigates cases rang- ing from the protection of endangered species to the cleaning up of hazardous waste sites. In other words, it serves as the nation’s environmental lawyer.. It enforces civil and criminal environmental laws to protect human health and the...
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A third area of resource exploitation that is useful to review in the context of environmental degradation is forests. At the time that European settlers began to ex- ploit the resources of the United States, forests cov- ered about two-thirds of the land. To many of the early settlers, these forests seemed endless, so cutting, burning, and re- moval went...
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“Superfund” because of the trust fund created by the act to fund cleanups, CERCLA is a comprehensive ap- proach to hazardous chemical dump and spill sites. It authorizes the president of the United States, through the EPA, to clean up facilities at which haz- ardous substances have been released. Petroleum substances not otherwise contaminated or listed as hazardous are exempted...
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Environmental law in the United States. Erosion is the gradual wearing away of the land sur- face by natural agents of water, wind, and ice. The land is de- graded because the soil that remains is of lower produc- tivity, and the sediment may damage crops or aquatic. Erosion also causes the soil to be less productive because the remaining...
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der the jurisdiction of the coastal state for specific purposes. The convention, the work of more than fourteen years of negotiation, is a comprehensive le- gal document that created an ordered system for the use of ocean space and for the protection of the natu- ral resources of the oceans.. According to customary use of the seas, the area be-...
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418 • Feldspars Global Resources. icut, to grind feldspar for the newly developed pottery industry in the United States.. The largest production of feldspar in the United States is in North Carolina, followed by Virginia, Cali- fornia, Oklahoma, Georgia, Idaho, and South Dakota.. China, Turkey, Italy, and Thailand jointly produce approximately 60 percent of the world’s total feldspar. production of...
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Beginning in the 1960’s, government land manag- ers used controlled burns and unopposed wildfires to clear away underbrush and dead trees in public for- ests. The political as well as economic infeasibility of con- trolling overgrowth may have contributed to South- ern California’s “Station Fire” of 2009, which ravaged roughly two hundred square miles of the Angeles Na- tional Forest...
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http://www.fws.gov/fisheries/fisheries.html. Law of the sea. Flax, also known as linseed, common flax, or Linum usitatissimum in Latin, is native to the region stretch- ing from the eastern Mediterranean to India. Flax was probably first domesticated in the Fertile Crescent and was cultivated extensively in ancient Egypt.. Various parts of the plant have been used to produce a variety of products,...
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However, the use of the term “food chain” dates from 1927, when Charles S. Elton described the implications of the food chain and food web concept in a clear man- ner. Food Chains in Ecosystem Description. Stephen Alfred Forbes, founder of the Illinois Natural History Survey, contended in 1887 that a lake com- prises a system in which no organism...