农业区非点源污染潜在危险性评价——以于桥水库流域磷流失为例

THE RISK ASSESSMENT OF NONPOINT POLLUTION OF PHOSPHORUS FROM AGRICULTURAL LANDS:A CASE STUDY OF YUQIAO RESERVOIR WATERSHED

在农业非点源污染研究中 ,确定农业非点源污染的关键源区或危险区域是开展有针对性研究和控制农业非点源污染的首要问题之一。本文在地理信息系统的支持下 ,综合考虑了影响于桥水库流域农业非点源磷流失的源因子和迁移因子 ,通过建立评价指标体系 ,计算磷污染危险性指数 ,对农业非点源磷流失危险性进行定量化评价 ,识别具有极高危险性或较高危险性的区域为磷流失的关键源区 ,将其作为控制和管理的优先区域和重点区域。结果表明 :流域中磷流失危险性极高和较高的区域即关键源区不到全流域面积的 6.0 %,危险性中等的地区占到整个流域面积的 2 0 .5 2 %;具有高和中等危险性的地区主要分布在流域河流两岸 ,且具有极高或较高的土壤有效磷含量或化肥磷施用量或高的土壤侵蚀强度 ,大部分为流域中部丘陵平原区的农田 ,少部分为地形较陡的山区农田。

The primary issue of efficiently controlling and managing agricultural nonpoint source pollution is how to identify critical source areas or the sensitive regions of pollutants loss from agricultural lands. In this paper, the assessment method of phosphorus index was introduced, and its application in the agricultural fields in Yuqiao reservoir watershed was carried out. The factors affecting phosphorus loss are classified in to source factors and transporation factors. The source factors mainly include soil available phosphorus, phosphorus fertilizer application rate and application method, and the transportation factors include soil erosion, runoff, and the distance of potential pollutant sources to streams. With the aid of GIS, the critical source areas with high risk or relatively high risk of phosphorus loss are identified and should be given a particular attention. The results showed that: the regions with relatively high risk of phosphorus loss cover less than 6.0 percent of total watershed area, and the regions with moderate risk of phosphorus loss cover 20.52 percent of total watershed area. The regions with high and moderate risk of phosphorus loss are mostly located along side the streams, where the highest or relatively high soil available phosphorus or phosphorus fertilizer, or intense soil erosion are observed.$$$$