丹江口水库核心水源区典型流域农业面源污染特征

为分析丹江口库区农业地表径流及其水质污染特征,识别流域水质污染风险变量,探究主要潜在污染物时空排放规律,估算流域污染负荷并分析污染物来源贡献,应用因子分析方法,通过周年常规监测,对核心水源区典型小流域的地表径流及其水质污染特征进行了分析,并探讨了其时间差异性。同时采用平均浓度法估算了流域内面源污染负荷量和各污染源类型对主要潜在因子负荷的贡献率。结果表明:流域内水体浊度、色度及流量在上游与下游间存在显著差异,总氮(TN)、总磷(TP)、化学需氧量(COD)、铵态氮(NH_4~+-N)、硝酸盐氮(NO_3~--N)、pH和电导率在不同监测断面间差异不显著;TN、TP、COD和流量是影响库区水质、造成污染风险的主要潜在因子;5—9月,随着降雨量和流量的增加,同步出现农业面源污染排放高峰。流域内,上、中、下游流域监测断面TN年负荷量分别为4.94、11.04、20.43 t,TP年负荷量分别为0.17、0.50、0.68 t,COD年负荷量分别为29.02、68.78、118.27t。农业生产及生活对TN贡献较大,规模化养殖对TP贡献较大,二者联合对COD负荷贡献率达到76%。研究表明,大量氮磷随水土流失进入水体是引起小流域面源污染负荷偏高的主要原因,加大对农业生活区和规模化畜禽养殖的控制管理,构建植被缓冲带等减少水土流失措施,对有效防治丹江口核心水源区典型小流域的面源污染具有重要作用。

Characteristics of surface runoff and agricultural non-point source pollution in the core water source area of the Danjiangkou Reservoir

Our objectives in this paper were to:analyze the characteristics of surface runoff and water quality pollution in the Danjiangkou Reservoir area; identify the risk variables of basin water quality pollution and explore the temporal and spatial discharge rules of major potential pollutants; estimate the basin pollution load and analyze the contribution of pollutant sources. Based on annual routine monitoring, we analyzed the characteristics of surface runoff and water quality in a typical small watershed by using factor analysis. Average pollutant concentration was used to estimate the non-point source pollution load and the contribution rate of each source type to the main potential factor load. The results showed that there were significant differences in water turbidity, color, and flow between upstream and downstream basin water bodies. There were no significant differences among different monitoring sections in total nitrogen(TN), total phosphorus(TP), chemical oxygen demand(COD), ammonium(NH₄⁺-N), nitrate(NO₃^--N), pH, and flow. TN, TP, COD, and flow rate were the main factors affecting the risk of water quality pollution in the reservoir area. With increased rainfall and flow, the agricultural non-point source pollution emission peak occurred between May and September. In the basin, the annual TN loads in the upper, middle, and lower reaches were 4.94, 11.04 t, and 20.43 t, respectively; the annual TP loads were 0.17, 0.50 t, and 0.68 t, respectively; and the annual COD loads were 29.02, 68.78 t, and 118.27 t, respectively. Agricultural production and life had large contributions to TN(accounting for 46%), while largescale farming had a major contribution to TP(accounting for 46%). Both contributed 76% of the COD load. It is concluded that the large amount of nitrogen and phosphorus associated with water and soil loss into the water body was the main reason for the high surface area pollution loads in small watersheds. Strengthening the control and management of agricultural living areas and reducing soil erosion by constructing riparian vegetation buffers significantly reduced the Danjiangkou non-point source pollution.