三峡库区典型流域农业面源氮素输出特征

Characteristics of Nitrogen Output from Agricultural Non-point Source in Typical Watershed of Three Gorges Reservoir Area

以三峡库区典型流域为研究单元,在自然降雨条件下,对流域出口设置的监测点进行连续取样观测。结果表明,2015年长坪流域在4-9月降雨量达703.1 mm,占全年降雨量的83.0%,径流量为686 354.4 m^3,占全年径流量的78.8%,径流量与降雨量显著相关(r=0.056,P<0.01);在此期间的总氮输出负荷占全年的88.7%,是流域氮素流失的主要时期,径流为流域面源氮素输出的主要渠道及主要驱动力;总氮年平均浓度为2.0 mg/L,浓度峰值主要出现在7-9月;TN、NO_3^--N、NH_4^+-N和PN的年输出负荷分别为9.0、6.6、0.4和1.9 kg/hm^2;NO_3^--N是氮素流失的主要形态,占总氮输出负荷的73.7%。

Taking the typical watershed in the Three Gorges Reservoir Area as the research unit,and the continuous sampling observation on the monitoring points of the watershed outlet set under the natural rainfall conditions were conducted. The results showed that in 2015,the Changping watershed rainfall in April-September reached 703.1 mm and the runoff amounting to 686 354.4 m3,accounting for 83.0% and 78.8% of the annual total respectively; And the runoff and rainfall were significantly correlated（r=0.056,P〈0.01）; During this period,the total nitrogen output load accounted for 88.7% of the whole year,which was the main period of nitrogen loss in the watershed, and the runoff was the main channel and driving force of the surface nitrogen export; The average annual total nitrogen concentration was 2.0 mg/L,the peak concentration mainly in July to September; The annual output loads of total nitrogen（TN）,nitrate nitrogen（NO3--N）,ammonia nitrogen（NH4＋-N） and particulate nitrogen（PN） were 9.0,6.6,0.4 and 1.9 kg/hm2,respectively. The main forms of nitrogen loss were nitrate nitrogen,accounting for 73.7% of the total nitrogen output load.