基于输出系数模型的南四湖流域非点源污染输出风险评估

[目的]探究非点源污染物N、P输出风险在不同子流域、坡度等级和县市区的分布特征,为南四湖流域不同风险区制定管理方案和控制对策提供科学依据。[方法]以数字高程模型(digital elevation model,DEM)为基础数据,运用ArcGIS软件,提取南四湖流域的DEM,制作坡度等级图,再运用水文分析功能,提取水系图、河流图、并划定子流域,结合2013年南四湖流域土地利用图,通过运用输出风险模型分析不同的土地利用类型和坡度下氮(N),磷(P)污染的空间变化。[结果]氮素的平均风险概率达到51.67%,磷素的平均风险概率达到9.14%,南四湖流域非点源污染输出风险湖东小于湖西;随坡度增大,高风险区面积减小,低风险区面积增加;就不同县市区而言,济宁市中区的N风险较小之外,其余县市区N风险均较大,P风险较小。[结论]N是流域最主要的非点源污染物,非点源污染输出风险大小与土地覆盖和坡度有密切关系。

Risk Assessment of Non-point Source Pollution in Nansihu Lake Basin Using Output Coefficient Model

[Objective] The objective of this study is to explore the distribution characteristics of the output risk of non-point source pollutants nitrogen(N) and phosphorus(P) under different conditions of sub basin, slope grade and geographical demarcation(counties), and to provide scientific basics for administer plan and control countermeasure of different risk areas of Nansihu Lake Basin.[Methods] Based on digital elevation model(DEM) data, the Nansihu Lake Basin DEM was extracted and slope grade was extracted using ArcGIS software. Then applying hydrologic analysis function, we extracted the drainage and river figures and delimited the drainage basin. Combined with the land use map of Nansihu Lake Basin in 2013, the space changes of N, P pollution under different land cover and slope were analyzed using the output risk model.[Results] The average risk probability of N reached 51.67%. The average risk probability of P reached 9.14%. The output risk of non-point source pollution in the east of lake was less than that in the west. With the increase of slope, the high risk area reduced, but the low risk area increased. In terms of geographical demarcation, Jining City was determined as less risk area of N, other counties had higher risk. The risk of P was less for all counties.[Conclusion] Nitrogen is the main basin non-point source pollutants. The output risk value of non-point source pollution has close relationship with land cover and slope.