太湖缓坡丘陵地区雨强对农业非点源污染物随地表径流迁移的影响

Rainfall Intensity Effects on Nutrients Transport in Surface Runoff from Farmlands in Gentle Slope Hilly Area of Taihu Lake Basin

以流域尺度为研究单元,流量、水质同步监测分析了雨强对太湖缓坡丘陵地区农田土壤养分随地表径流迁移的影响.10场降雨试验结果显示,雨强对农田氮、磷径流迁移有巨大影响.总磷、磷酸盐及氨氮EMC值随雨强的增强而增大;小降雨强度条件下,总氮、硝氮EMC值随雨强的增强而增大,强降雨条件下,其EMC值与雨强呈负相关.小雨、中雨、大雨及暴雨条件下,总氮及总磷的SMA值依次为1.91、311.83、127.65、731.69g/hm2及0.04、7.77、2.99、32.02g/hm2,与雨强表现出正相关.硝氮及氨氮是氮素迁移的主要类型,且主要是溶解态迁移.磷酸盐是磷迁移的主要形态.小降雨强度下,磷以溶解态迁移为主,随着雨强的增强,颗粒态磷迁移量逐渐增加,当雨强达到暴雨时,磷主要是颗粒态迁移.次降雨量、小时最大雨强、平均雨强及降雨历时影响因素中,氮、磷迁移量与小时最大雨强及次降雨量显著相关(p<0.01),均表现为正相关.

To investigate the effect of rainfall on agricultural nonpoint source pollution,watershed scale experiments were conducted to study the characteristics of nutrients in surface runoff under different rainfall intensities from farmlands in gentle slope hilly areas around Taihu Lake. Rainfall intensity significantly affected N and P concentrations in runoff. Rainfall intensity was positively related to TP, PO43^ --P and NH 4^＋ -N event mean concentrations（EMC）. However,this study have found the EMC of TN and NO 3^- -N to be positively related to rainfall intensity under light rain and negatively related to rainfall intensity under heavy rain. TN and TP site mean amounts （SMA） in runoff were positively related to rainfall intensity and were 1. 91,311. 83,127. 65,731. 69 g/hm^2 and 0. 04,7. 77,2. 99, 32. 02 g/hm^2 with rainfall applied under light rain,moderate rain,heavy rain and rainstorm respectively. N in runoff was mainly NO 3- -N and NH 4＋ -N and was primarily in dissolved form from Meilin soils. Dissolved P （DP） was the dominant form of TP under light rain,but particulate P （PP） mass loss increased with the increase of rainfall intensity and to be the dominant form when the rainfall intensity reaches rainstorm. Single relationships were used to describe the dependence of TN and TP mass losses in runoff on rainfall, maximum rainfall intensity,average rainfall intensity and rainfall duration respectively. The results showed a significant positive correlation between TN mass loss and rainfall,maximum rainfall intensity respectively （p〈 0. 01） and also TP mass loss and rainfall, maximum rainfall intensity respectively （p〈 0. 01）.