水污染的性质(专业英语).doc

Nature of water pollution
Water, one of man’s most precious resources, is generally taken for granted until its use is threatened by reduced availability(可用性) or quality. Water pollution is produced primarily by the activities of man, specifically his mismanagement of water resources. The pollutants are any chemical, physical, or biological substances that affect the natural condition of water or its intended use. Because water pollution threatens the availability, quality and usefulness of water, it is of worldwide critical concern.
The increase in the number and variety of uses for water throughout the world has produced a wide range of standards of water quality that must be satisfied. These demands include: ①preservation of rivers in their natural state; ②potability(饮用) of the water supply; ③preservation and enhancement of fish and wildlife; ④safety for agricultural use; ⑤safety for recreational(娱乐的) use including swimming; ⑥modation(适应;供应) to a great variety of industrial purpose; ⑦freedom from nuisance(有害的东西); ⑧generation of power for public utilities(公用事业)
; ⑨ dilution(稀释) and transport of wastes. Besides the specific chemical, biological, and physical requirements for the multitude of uses noted above, there are constraints(约束、限制) reflecting public health requirements, aesthetics(美学), economics, and short and long-term ecological impacts. Consequently, there is no ri