长三角典型村域次降雨条件下氮素非点源输出特征

研究长三角典型都市农业村镇不同土地利用下的氮素非点源输出特征,以期为治理该区域的面源污染提供科学依据.通过典型次降雨径流事件中氮形态和输出负荷变化的研究发现:监测点总氮(TN)的事件平均浓度(EMC)为20.01～22.83mg/L,其中溶解态氮(DN)占TN的比例最大;研究区非点源氮流失以溶解态为主,DN又以溶解态有机氮(DON)为主.耦合各形态氮浓度与径流量特征,发现非点源氮素输出呈现2个峰值,且出现在径流峰值之前4～55min;TN、DN和硝态氮(NO3--N)浓度随降雨时间增加呈现减少趋势;氮素负荷受其浓度和径流量的共同作用,基本上呈现与氮素浓度相同的变化特征,但起伏变化较为平缓.氮素污染负荷积累曲线分析表明,村域地表径流各形态氮素均存在初期冲刷效应.

Output Characteristics of Non-point Nitrogen from a Typical Village Region in Yangtze Delta Under an Individual Rainfall Event

In order to provide a scientific foundation for controlling non-point source pollution, we studied on output characteristics of non-point nitrogen under different land uses in a typical agricultural village in the Yangtze River Delta. The various species of nitrogen and output load under a typical individual rainfall runoff event were investigated. The results indicated that the event mean concentrations (EMC) of total nitrogen (TN) in monitoring sites ranged from 20.01 mg/L to 22.83 mg/L, and the main form was dissolved nitrogen (DN) in TN. The main form of the lost nitrogen in the studied area was DN which was mainly composed by dissolved organic nitrogen (DON). Coupled with the characteristics of nitrogen concentration and runoff, two peaks of non-point nitrogen output could be found, and appeared 4-55 min before the runoff peaks. The concentrations of TN, DN, and nitrate (NO^-₃-N) decreased with the rainfall time increasing. Nitrogen load was influenced by its concentration and runoff, and showed the same output characteristics of nitrogen concentration with a gentle variation. Form the cumulative load curve of nitrogen in a typical rainfall event, first-flush effect could be found for each nitrogen species in rural runoff.