三峡库区典型小流域氮磷流失特征

Characteristics on nitrogen and phosphorus losses in the typical small watershed of the Three Georges Reservoir area

为揭示三峡库区农业非点源物氮、磷流失的一般规律,以三峡库区秭归县的张家冲小流域为研究对象,自2005年1月至2006年4月,在自然降雨条件下,同步观测降雨、地表径流量,并对2次降雨径流的全过程进行了氮、磷浓度的测定,对降雨过程中径流量及污染物浓度随降雨-径流变化过程进行了监测研究.结果表明,长期干旱后的初期降雨径流中的氮、磷浓度明显高于雨季径流中的浓度,且氮、磷浓度变化与流量变化呈现出大致相同的趋势.降雨初期,氮、磷浓度随径流量的增大而升高;随着流量的继续增大,浓度呈现出下降趋势.对浓度随流量变化过程的监测表明,与基流中的浓度相比,总氮和硝态氮的浓度变化幅度较小,而氨氮和总磷浓度变化的幅度较大,其最大值分别是其最小值的10和67.5倍.溶解性的氨氮排放主要受降雨条件的制约,而径流中的磷主要是以颗粒态存在.通过对径流量和氮、磷排放负荷的多项式回归分析表明,TN、TP、NH4+-N和NO3--N的排放负荷和径流量之间存在着多项式关系,R2分别为0.9545、0·9740、0.9677和0.9504.

The relationships of pollutant concentrations and precipitatlon-runoff combined with natural rainfall events were monitored at the outlets of the Zhangjiachong watershed from January 2005 to April 2006. The results showed that nitrogen and phosphorus concentrations in earlier rainfall were higher than those in the later rainfall. Furthermore, the correlation could be confirmed hetween nutrients concentration and runoff. In earlier periods of precipitation, the concentrations of nitrogen and phosphorus increased with the increasing of flux. Then, they decreased with an increase in flux. Compared with the concentration in the base flow, a high variability of concentration range was obtained between the maximum and minimum values of ammoniac-nitrogen（ NH4^＋ -N） and total phosphorus（TP）. The maximum values of nitrogen and phosphorus concentrations were 10 and 67, 5 times than those of the minimum values, respectively, It could he concluded that the effluent of dissolved NH4^＋ -N was restricted by rainfall. The regression analysis results showed that polynomial relation existed between runoff and nutrient loads, and the R^2 values of TN, TP, NH4^＋ -N and NO3^- -N were 0.9545, 0. 974,0. 9677 and 0, 9504, respectively.