三峡库区小流域氮磷污染负荷估算

Nitrogen and Phosphorus Pollution Load Estimation in Small Watershed in Three Gorges Reservoir Area

申家河流域位于三峡库区腹心地带,是研究流域非点源污染的重要区域。根据忠县石宝镇石盘丘小流域降雨径流氮磷含量实测值,估算申家河流域氮磷流失量;同时为了进一步探索污染物从流域坡面到流域出口的迁移转化过程,提出了线性阶梯水库输入输出响应模型,借助激励响应卷积积分运算,建立了n阶污染物迁移转化数学模型。结果表明:旱田和林地是三峡库区申家河流域非点源污染的主要来源,二者累计贡献了90%以上的流域氮磷污染负荷;地表径流和壤中流氮磷负荷贡献率均呈现旱地>林地>水田>河渠的特点,因此申家河流域乃至整个三峡库区非点源氮磷污染控制的关键是拦截坡耕地农田的暴雨径流,并对林地加强水土保持措施的实施。另外,污染物迁移转化模型的提出是对非点源污染物在流域坡面的迁移和转化过程的数学模型化探索。研究结果以期为三峡库区典型流域非点源污染的估算提供参考,污染物迁移转化数学模型为进一步理论化研究迁移转化机理提供了理论支持。

Shenjiahe River watershed, which is located in the hinterland of the Three Gorges Reservoir area, is an important area to study watershed agricultural non-point source pollution. Values of nitrogen and phosphorus content in rainfall runoff in Shipanqiu small watershed of Shibao Town in Zhongxian County were monitored. The loss of nitrogen and phosphorus in Shenjiahe River watershed was estimated. In order to further explore the migration and the transformation process of pollutants from the basin slope surface to the basin outlet, a linear eascade reservoir response model with input and output was pro- posed. With the aid of stimulus-response convolution integral operation, a n-order mathematical model of pollutants migration and transformation was established. The results showed that dry lands and forestlands were the main source of non-point source pollution in Shenjiahe River watershed of Three Gorges Reservoir area, and the cumulative contribution of both to the watershed nitrogen and phosphorus pollution load was more than 90%. The nitrogen and phosphorus load contribution of subsurface runoff and interflow showed properties of dry lands 〉 forestlands 〉 paddy fields 〉 rivers and canals. So the key of nonpoint source nitrogen and phosphorus pollution control in Shejiahe River watershed and the whole Three Gorges Reservoir area was to intercept storm runoff from sloping farmland and to further implement soil and water conservation measures for forestlands. In addition, the pollutants migration and transformation process for non-point source pollutants in the basin slope surface were explored by mathematical model- ing, and it can provide scientifically theoretical support for further theoretical study of migration and transformation mechanisms. The results provide a reference for the estimation of non-point source pollution load in typical watersheds of the Three Gorges Reservoir area.