中文摘要：

氮素和磷素是引起水体富营养化的重要限制因子，本文通过人工模拟降雨的方法，对紫色土坡地在降雨后产生的氮磷迁移过程进行动态研究。结果表明，两种坡度（5°和10°）和不同降雨强度的模拟降雨过程中，供试的土壤产生两种径流模式：地表径流和壤中流。多场人工模拟降雨中，单场降雨造成坡地总氮（TN）最大迁移量达2．13kg·hm^-2，总磷（TP）最大迁移量达0．17kg·hm^-2，地表径流的总氮和总磷（NP）输出与壤中流NP输出相差3～5倍，地表径流是TP输出的主要途径，而地表径流TN输出与壤中流TN输出差异不显著，壤中流也是TN迁移的另一重要途径；在相同坡度和降雨强度条件下，农田作物的覆盖作用能减缓地表径流量和N、P的迁移量具有明显作用，但产流时间的差异不大；在相同作物覆盖和降雨强度条件下，坡度越大其地表径流量和TN的迁移量也越大，土壤的NP迁移主要以TN为主。通过模拟降雨发现紫色土坡地土壤NP流失浓度与径流流量之间的关系可以表示为：Gn=aQ^2＋bQ＋c，降雨量是影响参数b的主要因子。

英文摘要：

Nitrogen and phosphorus released through runoff to surface waters and drinking water systems represent a risk to human and environmental health. This study focuses on nitrogen and phosphorus loss from sloping land of purple soil with different slope gradients and rainfall intensities. Variable intensity field rainfall simulations were performed on 4.5 m longl.5 m wide 1 m depth plot, and overland runoff and subsurface flow were collected. Results showed that, with two slope（5° and 10° ）and different rainfall intensities, there were two runoff forms： overland runoff and subsurface flow. The TN loss maximum reached 2.13 kg·hm^-2 and the TP maximum loss reached 0.17 kg·hm^-2, and there were 3-5 times discrepancy in runoff rate between overland runoff and subsurface flow. With the same slope and rainfall intensity, the crop coverage increased the subsurface flow rate and reduced the NP loss and overland runoff rate, but there was not significant difference in the runoff-occurring time. With the same coverage and the same rainfall intensity, the TN loss and overland runoff went up as the slope increasing. The relationship between NP loss concentration （Cn）and runoff flux （Q）could be expressed by Cn= aQ^2 ＋ bQ＋ c and rainfall was major factor on influencing parameter b. So it is necessary to evaluate the eutrophication of the local surface water and ground water environment, and thereby to analyze the overall effects of different kinds of rainfalls.