水稻田非点源污染原位试验研究

为了研究野外水稻田的非点源污染,本试验采取一种新的原位观测方法:即在不改变水稻田原有出流特征前提下,在水稻生长季采集田面水水位和降雨信息,通过水位变化曲线计算水稻田每日的蒸散发和渗漏损失量,再根据水量平衡关系计算径流量.观测期间定期采集田面水测定总氮(TN)、总磷(TP)浓度,根据径流量和浓度估算非点源污染流出负荷量.试验选取北京市海淀区上庄镇某村水稻田试验田块,通过1年的试验观测得到在生长季内的37场降雨中共有9场降雨产生了出流.另外,还有2次人工排水和1次农田回归流形成了非点源污染.经计算试验区水稻田每个生长季TN输出系数为8.8 kg·hm-2,TP输出系数为0.47 kg·hm-2.该观测方法针对具有多出水口且最低田埂高度动态变化的野外水稻田的非点源污染观测具有较强的可操作性.

In situ experiment on non-point source pollution in paddy fields

A new in-situ method was adopted to investigate the non-point source pollution in real paddy fields. The evapotranspiration (ET) and infiltration loss were estimated on the basis of observed water-depth hydrograph and rainfall, and runoff volume was calculated through water balance approach. Surface water in the paddy fields was collected twice a week regularly to test the total nitrogen (TN) and total phosphorus (TP) concentrations. With the combination of runoff and observed surface water quality data, loads of non-point pollution from paddy fields were derived. The paddy field in Shangzhuang town in the northwest of Haidian district of Beijing was selected to study the on-point source pollution. Surface runoff occurred for nine times among 37 rainfall events during the whole growing seasons. In addition, two artificially drainages and one farmland return flow formed non-point source pollution. The results show that the TN and TP export coefficients in growing seasons was 8.8 kg·hm^-2 and 0.47 kg·hm^-2, respectively. The proposed method was more useful when the non-point source pollution is deserved in paddy fields with multiple outlets and dynamic variation of the lowest outlet height.