洱海流域农业面源污染空间分布特征及分类控制策略

作为典型的高原坝区农业型流域，洱海流域农业面源污染严重，威胁洱海水质.以洱海流域为研究对象，综合数理分析及GIS技术，开展流域农业面源污染负荷分析及评价，使用排污系数法估算了2018年洱海流域农村生活、畜禽养殖业和种植业污染中COD（化学耗氧量）、TN（总氮）、TP（总磷）的排放负荷，并通过等标污染负荷法在GIS空间分析反映流域内污染排放分布情况.结果表明:①2018年洱海流域农业面源主要污染物COD、TN、TP的排放量分别为11 188.20、2 752.56和259.33 t.COD排放量主要来自畜禽养殖，TN与TP的排放量均主要来自种植业.②洱海流域农业面源主要污染物COD、TN、TP等标污染负荷分别为559.41、2 752.56和1 296.63 m3/a.种植业等标污染负荷在总等标污染负荷中的占比最高，为36.40%，其次是畜禽养殖业，为34.44%.③各乡镇的等标污染负荷差异较大，等标污染负荷范围为（286.16±150.67）m3/a，等标污染负荷强度范围（0.13±0.067）m3/a.④聚类分析结果表明，洱海流域农业面源污染可分为种植业主导型、种植业高污染型、生活污染主导型和畜禽养殖业主导高污染型等4种类型.研究显示:来源于种植业的面源污染是洱海流域水环境保护需要控制的首要污染源，TN是需要控制的首要污染物；排放量与等标污染负荷的空间分布特征均呈流域北部乡镇污染物排放量较高，但流域西部各乡镇排放强度较大的特征；流域内各乡镇防治面源污染需要针对其污染来源特点分别采取推进种养平衡、推广绿色种植、分区控制农田径流以及推进农村生活污水治理等分类控制策略. 

Characteristics and Spatial Distribution of Agricultural Non-Point Source Pollution in Erhai Lake Basin and Its Classified Control Strategy

As a typical agricultural intensive watershed in the Yunnan Plateau, the Erhai Lake Basin is threated by serious agricultural non-point source pollution (ANPSP), which could play an important role in the deterioration of water quality. In order to investigate the ANPSP in the Erhai Lake Basin, the pollutant discharged coefficient method was used to calculate the discharges of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) from various sources in 2018. The analysis and evaluation of the ANPSP such as intensity, spatial distribution and classification were then carried out by utilizing the equivalent pollution load method, GIS technology and cluster analysis. The results showed that: (1) Total loads of COD, TN and TP from ANPSP in the Erhai Lake Basin were 11, 188.20 t, 2, 752.56 t and 259.33 t in 2018, respectively. COD discharge came mainly from livestock and poultry breeding, while TN and TP discharges came mainly from farming. (2) The equivalent standard pollution loads of COD, TN and TP from ANPSP in the Erhai Lake Basin were 559.41 m3/a, 2, 752.56 m3/a and 1, 296.63 m3/a, respectively. Farming had the highest proportion of the total equivalent pollution load at 36.40%, followed by livestock and poultry breeding at 34.44%. (3) The equivalent standard pollution loads varied widely among townships, with a range of (286.16±150.67)m3/a and a discharge intensity range of (0.13±0.067)m3/a. (4) The cluster analysis showed that the control regions and strategies can be divided into four types, including planting dominant area, serious polluted area of farming, rural domestic pollution area and livestock and poultry breeding dominant area. The study indicates that farming is the main source of non-point pollution of the water environment in the Erhai Lake Basin and TN is the primary pollutant to be controlled. The spatial distribution of discharges and equivalent standard pollution loads is characterized by higher discharges from towns in the northern part of the basin, while towns with higher discharge intensity are located in the western part of the basin. Accordingly, strategies should be adopted to promote the balance between farming and breeding, promote green planting and farmland runoff control, and improve the quality and efficiency of rural domestic sewage treatment in those 4 major control areas of ANPSP.