太湖地区小流域水文过程对氮素迁移的影响

Effects of the Hydrological Processes on Nitrogen Migration in a Small Watershed on the Taihu Lake

分析了太湖地区农业小流域逐日降雨径流和暴雨事件对氮素营养物输出的影响规律。结果表明:总氮、铵态氮和硝态氮流失日平均浓度随降雨量和径流量的增大而增大,总氮最大,硝态氮次之,铵态氮最小。暴雨事件中,径流起涨初期氮素浓度迅速升高,之后逐渐降低,在退水时期会有所反弹。暴雨事件中的瞬时流量与氮素输出浓度关系按流量大小可分为3段:在小流量段,氮素浓度低且数量平稳;中流量段,各态氮素流失浓度变化大;高流量段,总氮和铵态氮流失浓度显著降低并逐渐平稳,硝态氮浓度略为降低但变化较大。

The effects of daily rainfall runoff and heavy rains events on nutrient nitrogen output in the Taihu Lake agricultural watershed were analyzed. The results showed that the daily mean concentration in runoff of total nitrogen （TN）, ammonium nitrogen, and nitrate nitrogen increased with the daily rainfall and runoff increasing, and the loss of TN was the most, then followed by nitrate nitrogen and ammonium nitrogen. During the storm events,nitrogen concentration increased fastly at beginning of runoff,then decreased gradually, and there was a rebound in the period of withdrawal of water. The relationship of the discharge and nitrogen output could be identified 3 parts separated by the discharge ： Part 1 was the low discharge part,the concentrations of the nitrogen appear low and steady ; part 2 was the mid-discharge part, all the forms of the nitrogen concentration change acutely ; part 3 is the high-dischargc part ,the TN and ammonium concentration decrease obviously and tend to be steady,while the nitrate concentration decrease a little,and the values vary in a wide range.