最佳管理措施对非点源污染控制效果的预测——以北京密云县太师屯镇为例

选取北京市密云水库上游太师屯镇为研究区，针对该区农业非点源污染特征，设计了最佳管理措施(BMPs).同时，在非点源污染损失估算的基础上，率先尝试从经济学角度预测8种不同非点源污染措施在控制氮、磷和泥沙流失的效果及所获得的环境效益、经济效益，并将各单项措施的控制效率进行了比较分析.研究结果表明：改变土地利用类型的3种措施中，25°以上荒草坡还林措施效果最好，对总氮、总磷、泥沙流失的控制效果都超过15%，最高可达30%以上，且经济效益最大；25°以上坡耕地还林效果次之，对总氮、总磷、泥沙流失的控制效果都超过5%，最高可达12%；15°~25°坡耕地变果园措施最差，对总氮、总磷、泥沙流失的控制效果一般为4%~8%.坡度为0°~15°坡耕地在土壤侵蚀控制中具有重要地位；坡耕地植物篱和保护性耕作对土壤侵蚀类非点源污染的控制效果相近，削减的污染损失占非点源污染损失总价值的13%，具有明显的环境效益.针对畜禽养殖污染设计的农村户用沼气池，其经济效率在10%左右；测土施肥技术可减少氮素流失、节约大量化肥，且削减的污染损失达到非点源污染损失总价值的19%.作为综合污染控制措施的河岸缓冲带，可以有效地拦截氮、磷和泥沙的流失，对泥沙的控制效果最好，为83%，对氮的控制效果最低，仅为27%；而从经济效益方面比较，缓冲带减少氮素流失所获得的经济效益最大，约为该措施总经济效益的56%，泥沙次之，占28%；植被缓冲带削减非点源污染的总经济效率最高，可达35%，折合经济价值约1.69×106元.

Predicting effectiveness of best management practices for control of nonpoint source pollutiona case of Taishitun Town, Miyun County, Beijing

Best management practices (BMPs) are integrated approaches to prevent non-point source pollution by engineering and management practices. They are widely applied for agricultural nonpoint source pollution control because of their efficiency, economy and environmental benefits. Taishitun town, located in the upper watershed of the Miyun reservoir, Beijing, was selected to study and predict the effectiveness of pollution control and to assess the environmental and economic benefits of several BMPs by using the methodology of environmental economics. After comparison of the efficiencies of various BMPs, the conclusions are as follows; ①Among three practices to change land use, returning grassland to forest on slopes 25° or greater has the best control effect on nitrogen, phosphorus and sediment, providing 15% ～ 30% reduction and the highest economic benefit. Returning farmland on slopes 25° or greater to forest has the second best control effect on nitrogen, phosphorus and sediment loads. Returning farmland on slopes 15°～25° to orchard has the lowest reduction ranging from 4% to 8% . Lands with slopes 0°～ 15° have the key role in soil erosion control. There are notable environmental benefits of using hedgerows on sloping land and conservational cultivation. These practices reduce up to 13% of the total nonpoint source pollution. ② Marsh gas tanks for rural households have general economic efficiency that can reduce around 10%of nonpoint source pollution. Balanced fertilizer application technology can reduce the loss of nitrogen and save fertilizer, reducing the total loss up to 19%.Riparian vegetation buffers are an integrated pollution control practice which can decrease the load of sediment by 83% and that of nitrogen by 27%. The economic values of the decreased nitrogen and sediment losses are up to 56% and 28% of the total.Implementing riparian vegetation buffers is the most effective BMP with an economic efficiency of 35% of nonpoint source pollution control and its equivalent economic value amounts to 1.69 million RMB.