密云水库流域农业非点源污染基本特征分析

通过对密云水库上游流域8个乡镇化学肥料、畜禽粪便、水产养殖等农业非点源污染的调查统计和监测,初步明确了该区域农业非点源污染的基本特征：（1）化肥的不合理使用和坡耕地耕作为该区域农田养分流失的主要原因,区域内农用坡耕地2005年流失氮素19.2 t,流失磷素5.5 t,流失养分的主要来源为施用的化肥;（2）流域内畜禽粪便污染负荷区域间差异明显,部分乡镇畜禽粪便环境污染风险大;（3）流域内水产养殖排放水体水质50%不达标,加剧了下游水体的富营养化.

Characteristics of Agricultural Non-Pointed Source Pollution in the Watershed of Miyun Reservoir

Due to strict control of point source pollution, non-point source (NPS) pollutants became a chief source of pollution in the watershed of Miyun reservoir. Since agricultural structure changed in recent years, current NPS pollution from agriculture was in urgent need of being understood fully, for the prospect of water quality and environment protection. Therefore, NPS pollutants from agriculture, including chemical fertilizers, waste released from livestock and poultry, polluted water from aquafarms were investigated and monitored in this area. The characteristics of agricultural NPS pollution in this area were: (1) Amount of chemical fertilizers used in the watershed decreased in recent years. Nitrogen and phosphorus loss from farmland in 2005 was about 19.2 t and 5.5 t, respectively, resulted from improper fertilization and cultivation on sloping farmland. Majority of nutrients was lost via sediment movement after rain. (2) Loads of the waste from livestock and poultry varied with different regions, with high risk to the environment in some area. (3) Concentration of nitrogen and phosphorus in 50 percent of waste water samples taken from 12 aquafarms, exceeded the limitation concentration of the national standard of surface water quality, which would contribute to water eutrophication in downstream.