不同坡度下紫色土坡耕地径流与氮素流失特征

Characteristics of Runoff and Nitrogen Loss from Slope Cropland under Different Slope Gradients in the Hilly Area of Purple Soil

采用野外径流小区对紫色土丘陵区2013年4次典型降雨产流事件进行了监测，研究了不同坡度下地表径流和壤中流产流及氮素流失特征。结果表明：自然降雨条件下，地表径流与壤中流径流量随坡度的增加呈先增大后减小的趋势。径流方式对紫色土坡耕地径流氮素质量浓度和排放通量具有明显影响。壤中流中的总氮排放浓度与氮流失通量在不同降雨条件不同坡度下的变化趋势与壤中流径流量的变化一致。在不同坡度下，壤中流中的氮素浓度比地表径流低，但氮排放通量是地表径流的1．15～4．18倍，以壤中流形式形成的氮素损失是紫色土坡地氮素迁移的主要方式。紫色土坡地径流量和径流中流失的氮浓度及通量都存在一个临界坡度值。研究结果可为调控长江上游紫色土丘陵区氮素流失提供参考。

In order to better understand the characteristics of runoff and nitrogen loss in the slope cropland of purple soil under different slopes ,four rainfall-runoff events were monitored by using field runoff observation method in the hilly area of Sichuan Basin in 2013 .The results indicated that the discharges of overland flow and interflow increased first and declined then at a critical slope gra-dient with slope gradient increasing at natural rainfall .Concentrations and the flux of nitrogen were greatly affected by overland flow and interflow process .Concentration and flux of nitrogen in interflow were both significantly interrelated with the discharge of inter-flow under different rainfall and slope gradients .Nitrogen concentration in interflow was less than that in overland flow .However , the transport load of nitrogen in interflow was 1 .15-4 .18 times more than that in overland flow because the percentage of interflow accounting for total runoff was much higher .It indicated that interflow was the main transport pathway of nitrogen .There existed critical slope gradients in which plots the discharge of overland runoff and interflow achieved maximum in the four rainfall-runoff events ,as well as the concentration and flux of nitrogen .This research provides a reference for the non-point source pollution control in the hilly area of purple soil .