三峡库区典型小流域农业非点源氮磷流失特征

Characteristics of agricultural non-point source nitrogen and phosphorus losses in a typical small watershed in Three Georges Reservoir area

基于2007—2009年的野外观测数据对戴家沟小流域降雨径流与农业非点源氮磷流失的时间序列变化关系及其特征进行研究。结果表明:2007—2009年,戴家沟小流域降雨量和径流量峰值变化一致,二者相关系数为0.904。总氮和总磷浓度变化趋势吻合,但总氮对降雨径流变化响应的灵敏度高于总磷;氮流失浓度受降雨径流变化影响显著,而磷流失则表现出逐年递增的趋势;氮磷比的变化特征与总氮浓度的变化特征一致,且与径流波动有良好的耦合关系。2007—2009年,戴家沟小流域降雨径流量累积百分比峰值出现时刻与总氮、总磷流失量累积百分比峰值出现时刻不吻合,表明流域农业非点源污染具有较大的随机性和分散性,二者没有严格的对应关系。

This paper studied the time series variations of agricultural non-point source nitrogen and phosphorous losses and their relationships with rainfall-runoff in the Daijiagou small watershed（0.67 km2） in Three Georges Reservoir area,based on the 2007-2009 field observation data.In 2007-2009,the peak values of the rainfall and runoff in the watershed had the same variation trend,with the correlation coefficient as high as 0.904.The total nitrogen（TN） and total phosphorus（TP） losses also showed a same variation trend,but the TN loss was more sensitive to the variation of rainfall-runoff,as compared to TP loss.The TN loss fluctuated with rainfall-runoff,but the TP loss showed an increasing trend year by year.The variation pattern of N/P ratio accorded with that of TN concentration,and showed a good coupling relationship with the runoff fluctuation.The peak time of the cumulative percentage of rainfall-runoff was not consistent with that of TN and TP losses,suggesting that the agricultural non-point source nitrogen and phosphorous pollution in the watershed was of random and dispersive,and there was no strict parallelism relationship between the nitrogen and phosphorous pollution.