基于流域尺度的农业非点源污染物空间排放特征与总量控制研究

农业非点源污染是导致流域水质恶化的重要原因之一.依据农业污染源主要污染物空间排放特征和排放强度分析，划分农业非点源污染空间管理分区，并研究设计分区污染物总量控制方案，是提高农业非点源污染控制成效的重要途径之一.以湖北省四湖流域为研究案例区，系统开展了流域尺度的农业非点源污染空间排放特征识别与总量控制研究.结果表明，四湖流域水环境COD、总氮、总磷、氨氮负荷主要来自于农业非点源污染，4类非点源污染物分别占到流域污染物排放总量的67.6％、 82.2％、 84.7％和50.9％.对四湖流域非点源污染物空间排放特征分析结果表明，水产和畜禽养殖业发达的洪湖、监利、潜江、沙洋地区是流域非点源污染物的主要贡献源区.根据污染物在流域空间上的排放特征和源强评价结果，将四湖流域划分为3个农业非点源污染管理分区，即长湖上游水产和畜禽养殖污染重点控制区、四湖干渠农村非点源污染综合控制区和洪湖水产养殖污染重点控制区，针对不同管理分区分别提出了污染控制措施.基于水质改善和水体纳污能力综合考虑，设计了针对3个非点源污染管理分区的总量控制方案，分阶段实现监测断面全指标达标和满足水体纳污能力要求.主要污染物中，COD主要削减区域为四湖干渠区和洪湖区，分别占到流域COD削减量的43％和42％；氨氮主要削减区域为四湖干渠区，占到氨氮总削减量的66％；总氮主要削减区域为四湖干渠区和洪湖区，分别占到流域总氮削减量的42％和31％；总磷主要削减区域为四湖干渠区，占到流域总磷削减量的53％.

Spatial Discharge Characteristics and Total Load Control of Non-point Source Pollutants Based on the Catchment Scale

Agricultural non-point source pollution is one of the major causes of water quality deterioration. Based on the analysis of the spatial discharge characteristics and intensity of major pollutants from the agricultural pollution source, the establishment of spatial management subzones for controlling agricultural non-point pollution and a design of a plan for total load control of pollutants from each subzone is an important way to improve the efficiency of control measures. In this paper the Four Lake basin in Hubei Province is adopted as the research case region and a systematic research of the control countermeasures of agricultural non-point pollution based on the catchment scale is carried out. The results shows that in the Four Lake basin, the COD, total nitrogen, total phosphorus and ammonia nitrogen load of the water environment are mainly caused by agricultural non-point pollution. These four kinds of non-point source pollutants respectively account for 67.6%, 82.2%, 84.7% and 50.9% of the total pollutant discharge amount in the basin. The analysis of the spatial discharge characteristics of non-point source pollutants in the Four Lake basin shows that the major contributor source regions of non-point source pollutant in the basin are the four counties, including Honghu, Jianli, Qianjiang and Shayang where the aquatic and livestock production are relatively developed. According to the spatial discharge characteristics of the pollutants and the evaluation of the discharge intensity of pollutants, the Four Lake basin is divided into three agricultural non-point pollution management subzones, which including Changhu upstream aquatic and livestock production pollution control subzone, Four-lake trunk canal rural non-point source pollution control subzone and Honghu aquatic production pollution control subzone. Specific pollution control measures are put forward for each subzone. With a comprehensive consideration of the water quality amelioration and the allowable discharge of pollutants, a total load control solution is designed for the three non-point pollution management subzones, so as to fulfill the requirements of all indices of the monitoring sites and the requirements for the allowable discharge of pollutants of the water. Among the major pollutants, the major COD reduction area includes the Four-lake trunk canal subzone and the Honghu Lake subzone, which respectively account for 43% and 42% of the total COD reduction amount; the major ammonia nitrogen reduction area includes the Four-lake trunk canal subzone, accounting for 66% of the total ammonia nitrogen reduction amount; the major total nitrogen reduction area covers the Four-lake trunk canal subzone and the Honghu Lake subzone, accounting for 42% and 31% of the total nitrogen reduction amount in the basin respectively; the major total phosphorus reduction area is the Four-lake trunk canal subzone, accounting for 53% of the total phosphorus reduction amount in the basin.