中文摘要：

通过调查抚仙湖1981-2005年水体N、P变化，以及监测该流域33条主要入湖河道水体N、P的输入情况，从而揭示抚仙湖水体N、P变化规律及该流域非点源污染主要特征。结果表明，近20多年来，抚仙湖水体N素水平增长迅速而P素水平稳定，2001-2005年表层水体TN：TP平均值达到33．06，P素成为抚仙湖水体藻类生长的主要限制因子之一。2005年，抚仙湖33条主要入湖河道TN和TP输入量分别为528．3t和70．7t，抚仙湖北部澄江县已成为非点源污染源最为严重区域，化肥的过量施用和畜禽养殖规模的过快发展已成为该流域非点源污染的主要原因。

英文摘要：

Protecting water resources from non-point source pollution is an important public-health concern and a major national environmental issue. Based on the water body investigation and monitoring results from 33 influx rivers of total nitrogen and total phosphate, the nonpoint source pollution characteristics in the watershed and the variation law of total nitrogen and total phosphate were identified in Fuxianhu Lake from 1981 to 2005. The results demonstrated that the total nitrogen in water body increased quickly, however, the total phosphate in water body was stable from 1981 to 2005. The average ratio of total nitrogen to total phosphate was as high as 33.06 from 2001 to 2005. Phosphate has become one of the mainly limited factors for alga growth. It can be seen that the influx mass for total nitrogen and total phosphate are 528.3 t and 70.7 t separately. The north of Fuxianhu watershed, Chengjiang County, is the most severe polluted area because of the overuse of fertilizes and extensively bloom of livestock and poultry raising. The findings of this paper help to explore the distribution and mig-ration of nitrogen in agricultural lands, as well as to explore the characteristics of non-point source pollution resulting from agricultural activities. The work presented in this paper is also believed to be useful in formulating management strategies for extensive cropping watershed to reduce diffusive pollution from agricultural activities.