非点源污染的管理及控制

非点源污染是指溶解的或固体污染物从非特定的地域，在降水和径流冲刷作用下，通过径流过程而汇入受纳水体引起的水体污染，主要起源于土壤侵蚀，农药与化肥的施用，农村家畜粪便与垃圾，农田污水灌溉，城镇地表径流，林区地表径流和大气干湿沉降等污染源。

Non-point Source Pollution Control and Management

Compared to point source pollution,non point source pollution is more common and severe and its management is also more challenging.Non point source pollution originates from diffuse areas where some solvable or solid pollutants are produced.When these pollutants enter the waterbodies,such as lakes,river,reservoir and gulf with runoff during rainy season,water pollution or eutrophication could be induced.Normally,the soil erosion,application of chemical fertilizer and pesticide in farmland,piling of domestic animal's excrement or garbage in rural areas,surface runoff from urban areas and forest areas,irrigation with waster water in farmland and air dry wet deposit are considered as the principal sources of non point source pollution.Due to the influence of various factors,non point source pollution is characterized by random process,complex mechanism,widespread distribution,latent occurrence.Thus a practical difficulty is remained to study and control non point source pollution.Apart from sources,adverse effects and characteristics of non point source pollution were analyzed in this paper,the experiences and methods on managing and controlling non point source pollution in USA were also introduced.It will be helpful for Chinese government to make a feasible decision on this issue.