农田降雨径流污染模型探讨 ——以上海郊区农田氮素污染模型为例

农田降雨径流污染是非点源污染研究中的一个重要问题，估算其发生负荷的难度很大。通过对农田降 流污染模型结构的理解和适当简化不可直接建械的部分，对农田非点源污染物输出的重要环节－－降雨径流和污染物迁移进行了模拟。根据实测资料对SCS法的部分参数作了修正，使小块农田的降雨径流关系适合上海的区域自然地理条件；采用比较完善的径流试验资料建立了相应的径流单位线；并利用水流流速与固体颗粒被冲刷强度的关系，选择合适的试验资料，分析得到了径流过程与氮素流失浓度的相关关系，从而建立了以修正的SCS法、径流单位线和径流过程与氮素流失浓度的关系为基础的农田降雨径流污染模型。在具备较长系列降雨量资料的条件下，该模型确定了不同降雨量频率代表年份上海郊区农田氮素的年流失量。

ON FARMLAND PRECIPITATION-RUNOFF NONPOINT POLLUTION MODEL FARMLAND NITROGEN POLLUTION MODEL IN SHANGHAI SUBURBS

Farmland precipitation-runoff nonpoint pollution is one of themost important problems in nonpoint pollution problem. It is very difficult to estimate its loading. Through deeply studying model construct, the authors simplify part item, which couldn' t. set up model directly. The process of precipitation-runoff and pollutant transportation was simulated. After analyzing data of real measure, part parameters of SCS was amended and the relationship of precipitation-runoff suiting physical geography of small farmland in Shanghai was made. Using excellent data of precipitation-runoff, the anthors found the unit line of runoff. According to similar changing relationship between water velocity and solid particulate matter flowing intensity, selecting suitable data, they researched and got correlated between course of precipitation-runoff and concentration of nitrogen pollutant transportation. Basing these working, we set up farmland precipitation-runoff nonpoint pollution model basing on amended SCS, unit line of runoff, relationship of process of precipitation-runoff and concentration of nitrogen pollutant transportation. When getting long series data of precipitation, the model could estimate the annual loss of farmland nitrogen in different model age on frequency of precipitation.