太湖地区何家浜流域初期雨水对水稻田污染物的冲刷效应

Effects of rainfall-induced flush on pollutants from rice-field in Hejiabang Creek Basin of Tai Lake region

为研究农田非点源污染物在降雨过程中初期冲刷效应的变化规律,在太湖地区何家浜流域划定若干块水稻田作为研究区域,并分别选取单块封闭水稻田沿河岸的直入河点和多块水稻田沿沟渠汇流后的沟渠入河点为采样点,对比封闭小区域和非封闭大区域污染物输移的特征,通过监测在降雨-径流过程中的水量、水质,并结合相关分析方法,分析降雨初期污染物的冲刷规律。结果表明,初期雨水对水稻田污染物的冲刷强度从颗粒态悬浮物(SS)、颗粒态氮(PN)、颗粒态磷(PP)到溶解态氮、磷逐渐减弱,其中最明显的是SS,定义新的雨水初期冲刷效应强度量化考核指标后,计算得各主要指标的冲刷效应强度I值从大到小依次为:SS(0.059 3)>PP(0.021 2)>TP(总磷,0.013 0)>TN(总氮,0.006 8)>PN(0.004 6)>PO3-4-P(磷酸盐,0.003 7)>NN(硝态氮,-0.002 8);封闭小区域的初期冲刷效应非常明显,非封闭大区域的初期效应相对较弱,比较小区域和大区域,颗粒态污染物如SS、PP和PN等初期冲刷效应被弱化的程度较小,溶解态污染物如NN、PO3-4初期冲刷效应被弱化的程度较大。

In order to investigate the effects of variation law of rainfall-induced flush on agricultural non-point source pollution,several rice-fields in Hejiabang Creek basin of Tai Lake were chosen as the research region. A sampling point where water flew from a single closed rice-field to the river and another sampling point where collected ditch water from the end of several rice-fields were selected. The pollutant transport law of the two investigated sampling points was compared. Combined with related analysis and the monitoring results of quality and quantity of the water during the rainfall-runoff flow process,the law of rainfall-induced flush effect was discussed. Results showed that rainfall-induced first-flush effect on particle pollutants such as suspended solids（ SS）,particulate nitrogen（ PN） and particulate phosphorus（ PP） was more obvious than dissolved pollutants such as phosphate（ PO3-4-P） and nitrate nitrogen（ NN）. By redefinition the quantitative evaluation index of rainfall-induced effect,the main indexes of average rainfall-induced first-flush effect strength value I were calculated,which were SS（ 0. 059 3）,PP（ 0. 021 2）,total phosphorus（ TP,0. 013 0）,total nitrogen（ TN,0. 006 8）,PN（ 0. 004 6）,PO4^3--P（ 0. 003 7）,NN（- 0. 002 8） in series. Small enclosed area showed obvious first flush effect compared with large non-enclosed area. Comparing small area with large area,the first-flush effects were insignificantly weaken for particulate pollutants such as SS,PP and PN,however they were obviously weaken for dissolved pollutants such as NN and PO3-4-P.