近30年来中国西部河谷型城市水体污染变化趋势与机制

The Changing Trend and Mechanism of Water Pollution of Valleycity in the West of China during Recent 30 Years

主要利用统计资料研究了中国西部河谷型城市近20～30年来水环境污染的变化趋势和水环境污染的发展阶段。在此基础上，从单位工业增加值排放强度、污染物的排放与治理、治理能力等角度总结了我国西部河谷型城市水环境污染的机制。

Natural water is contaminated by human activity. This phenomenon is the water environment pollution. Because of the entrance of certain substance, some attributes of water which contain the physical, chemical, biologic or radioactive aspect are changed. As a result, the effective use of water is influenced and the human health or the zoology environment is in danger. Water environment pollution is formed by the living discharge water and industrial discharge water. It can be evaluated by some indexes, such as COD, oil, coliform, Cr^＋6, Hg, Pb, nonionic ammonia, volatilization hydroxybenzene and pH. By analyzing the statistic data mostly, the paper researches the changing trend and developing phases of the pollution of water environment of the valley-clties in the west of China during resent 20 ～ 30 years. Then it summarizes the mechanism of the pollution of water environment of the valley-cities in the west of China from the points of the drain intensity per industrial gain, the drain and settlement of contamination and the ability of management. By analysing, the pollution of river of the valley-city in the west of China is less than the one during 1970～1980 since 1990. For example, the main streams and branches of surface water of Changjiang River of the valley-city in the west of China become less contaminated apparently, and most of them are the light pollution, and the first or second water quality. However, the pollution of Yellow River doesnt become less apparently. Most parts of reaches are more than the middle pollution, and a great many of them are the heavy pollution and the serious pollution. The water quality of Lhasa River and Urumchi River is preferable. Analyzed the development passages of the water pollution of city, the drain of industrial discharge water and living discharge water separately is increasing along with the increase of GDP per capita on the whole. However, the use of living water per capita and the drain of industrial discharge water per GDP separately are increasing early, and declining late. The shape of the trend looks like ＂U＂. In the terms of mechanism of water pollution, the drain intensity of discharge water per industrial gain and the settlement rate of contamination of water are higher. In parts of cities, the drain of contamination is still higher. In addition, Transition of contamination from upriver to downriver is also the reason which causes the serious pollution of water of the valley-city in the west of China mainly.