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British petrochemical corporation. Formed in 1909 as the Anglo-Persian Oil Co., Ltd., to finance an oil-field concession granted by the Iranian government to William Knox D'Arcy, it became one of the largest oil companies in the world, with oil fields and refineries in Alaska and the North Sea. The British government was for many years BP's largest single stockholder, but by the late 1980s it had turned over the company to private ownership. In 1987 BP consolidated its U.S. interests by acquiring the Standard Oil Co. In 1998 it merged with Amoco (formerly Standard Oil of Indiana) to form BP-Amoco. In addition to oil and natural gas, it produces chemicals, plastics, and synthetic fibres. Its headquarters are in London.
State resulting when substances are released into a body of water, where they become dissolved or suspended in the water or deposited on the bottom, accumulating to the extent that they overwhelm its capacity to absorb, break down, or recycle them, and thus interfering with the functioning of aquatic ecosystems. Contributions to water pollution include substances drawn from the air (see acid rain), silt from soil erosion, chemical fertilizers and pesticides, runoff from septic tanks, outflow from livestock feedlots, chemical wastes (some toxic) from industries, and sewage and other urban wastes from cities and towns. A community far upstream in a watershed may thus receive relatively clean water, whereas one farther downstream receives a partly diluted mixture of urban, industrial, and rural wastes. When organic matter exceeds the capacity of microorganisms in the water to break it down and recycle it, the excess of nutrients in such matter encourages algal water blooms. When these algae die, their remains add further to the organic wastes already in the water, and eventually the water becomes deficient in oxygen. Organisms that do not require oxygen then attack the organic wastes, releasing gases such as methane and hydrogen sulfide, which are harmful to the oxygen-requiring forms of life. The result is a foul-smelling, waste-filled body of water. See also eutrophication.
© 2010 Encyclopædia Britannica, Inc.
