蟹、鱼网围混养对草型湖泊氮磷平衡的影响

富营养化是当今的水污染治理难题，而农业非点源磷污染与水体富营养化的发生有着密切的关系，目前农田生态系统中广泛存在的磷素投入过量和由此导致的土壤磷素积累加剧了磷素向水体的流失。本文根据国内外最新研究成果，分析了农田土壤磷素流失对水体富营养化的影响，指出了减轻农业非点源磷污染的重要性，对目前所采用的农业非点源磷污染重点控制区的确定方法和一些主要防治措施的效果进行了评述。

Effects of Pen Fish and Crab Polyculture on Burden of Nitrogen and Phosphorus in Aquatic Environment of Weed-type Lakes

Phosphorus from agricultural non-point sources has been identified as the main cause of freshwater eutrophication throughout the world and contributes a large share to the water quality deterioration. With excessive amount of phosphorus being input to the agro-ecosystem, the accumulation of P in cultivated soils has increased the potential for P loss in agricultural runoff and drainage. This paper attempts to summarize the research activities focused on the build-up of P in soil, the interaction of P with soils and its transport in surface and subsurface drainage. Phosphorus indexing system(PIS) used for identifying sites vulnerable to phosphorus loss in agricultural runoff is introduced. Widely practiced mitigation options include nutrient budgeting, input management, soil conservation, land use management and the establishment of vegetated riparian zones, buffer strips and sedimentation ponds which have been proved to be very cost effective in a Chinese context.