模拟降雨条件下农田地表径流与壤中流氮素流失比较

Comparative Study of Nitrogen Losses between Surface Flow and Interflow of Farmland under Artificial Rainfall Conditions

选择太湖流域平原河网地区为试验地点,采用3次重复人工暴雨试验方法,研究暴雨径流过程中地表径流与壤中流氮素流失特征。结果表明:地表径流与壤中流氮素流失特征具有较大差异,地表径流水相TN平均浓度为12.41 mg/L,壤中流水相TN平均浓度低于地表径流约50.65%。地表径流氮素流失以PN为主,DN和PN的流失量比为1∶2.65,壤中流氮素流失以DN为主,DN和PN流失量比为2∶1。整个暴雨径流过程中氮素流失以地表径流为主,占总流失量的81.66%,壤中流氮素流失量相对较少,仅占氮素总流失量的18.34%。地表径流与壤中流氮素流失量比较分析结果证实,土壤的水分下渗滤过机制对氮素具有较强的削减作用,对PN的削减作用尤为明显,可达70%以上。在流域产汇流过程中,充分发挥洼地和高透水地段对地表径流的蓄渗功能,对面源营养盐污染控制具有重要的作用。

Selecting river network plain in Taihu basin as experiment places, triple duplication experiments have been carried out under the artificial rainstorm conditions to evaluate the characteristics of nitrogen losses from surface flow and interflow. The results show that there are significant differences between nitrogen losses in surface flow and that in interflow. Average concentration of total nitrogen in surface flow is 12.41 mg/L, which is higher than that in interflow. The average concentration of nitrogen in interflow only accounts for about 50.65 % of the concentration in surface flow. The main form of nitrogen loss in surface flow is particulate nitrogen, and the ratio of dissolved nitrogen to particulate nitrogen is 1 ： 2.65. However, the nitrogen loss form in interflow is dissolved nitrogen mostly, and the ratio of dissolved nitrogen to particulate nitrogen comes to 2 ： 1. In the whole rainstorm process, nitrogen losses by surface flow take the big proportion, account for 81.66% of the whole, and only 18. 34% of the whole nitrogen losses is by interflow. According to the comparative analysis results of nitrogen losses between surface flow and interflow, it is confirmed that soil infiltration has strong nutrient decay function, which especially is obvious for particulate nitrogen, reaching more than 70%. During the runoff output and routing process, lowland and high-pervious surface can be used for runoff storage and infiltration, which play an important role in control of non-point source pollution.