基于非点源污染的密云水源保护区水环境容量核算及其分配

根据密云水库一级保护区内河流、水文、污染物特征,采用输出系数法模型进行研究区非点源污染负荷估算,并以COD、氨氮和总磷为控制因子,建立一维河流水质模型,定量计算研究区水环境容量,在此基础上,对研究区水环境剩余容量及污染排放削减量进行分配。结果表明:研究区非点源污染负荷输出总值分别COD433.84t/a、氨氮47.14t/a和总磷40.75t/a,4种非点源污染类型中畜禽养殖的COD、氨氮和总磷分别占各项总污染负荷的78.6%、60%、87.1%,成为保护区内主要的污染来源,水土流失污染、农村生活污水依次之,民俗旅游的污染负荷贡献率最低;污染源类型中,生活和民俗旅游污水则主要造成COD污染,而水土流失主要引起氨氮和总磷污染。保护区内COD、氨氮和总磷的水环境容量分别为3 170.36t/a、128.20t/a、25.27t/a,相较于污染负荷,水环境容量偏小。其中,总磷的污染风险最大,其环境剩余容量达到负值,应对其进行总量15.48t/a的削减。秉承公平和效益原则,总磷排放量削减分配中,畜禽养殖、生活污水、民俗旅游、水土流失各污染源的削减比例分别为44.26%、10.83%、40.90%、6.15%;氨氮的水环境剩余容量分配中,畜牧养殖的分配量最小、分配比例最低(14.16t、49.85%);畜牧养殖成为研究区内重点削减和控制的污染源。基于非点源污染的水环境容量计算及其分配研究可为保护区水环境控制管理与污染防治提供科学依据与决策支持。对加强密云水库饮水源保护,控制上游污染源,保证水质安全,确保北京市民人体健康和经济发展具有重要意义。

ESTIMATION AND ALLOCATION OF WATER ENVIRONMENT CAPACITY IN THE FIRST-GRADE PROTECTING AREA OF MIYUN RESERVOIR BASED ON NON-POINT SOURCE POLLUTION

According to the characteristics of the rivers, hydrology and contaminant in the first-grade protection zone of Miyun Reservoir, a one-dimensional water quality model which regarded COD, ammonia nitrogen and total phosphorus as control factors was established, and then used to estimate the water environmental capacity in the study area. Besides, the non-point source pollution load was calculated through the export coefficient model and the water environment residual capacity and pollution reductions were allocated. The results showed that: the outputs of non-point source pollution load were 433.84t/a for COD, 47.14t/a for ammonia and 40.75t /a for total phosphorus. COD, ammonia nitrogen and total phosphorus of livestock accounted for 78.6%, 78.6%, 87.1% of the total pollution load. The poultry farming contributed the greatest to the non-point source pollution. COD was mainly caused by living and travel waste, while the pollution of ammonia nitrogen and total phosphorus was mainly caused by water and soil erosion. The water environment capacity of COD, ammonia nitrogen and total phosphorus in the protection zone were 3170.36 t/a, 128.20 t/a, 25.27 t/a, which were smaller than the pollution load. The total phosphorus pollution was of great risk, and the environment remaining capacity was negative and should be reduced by 15.48 t/a. Combined with the principles of fairness and efficiency, the total phosphorus reduction rates from the sources of livestock, sewage, folk tourism, soil erosion were 44.26%, 10.83%, 40.90%, 6.15%, respectively. For the allocation of ammonia nitrogen in water environment remaining capacity, the livestock got the minimum distribution ratio (14.16t, 49.85%). Calculation and distribution of water environmental capacity of non-point source pollution may provide a scientific basis and decision support for protected areas management and water pollution control environmental control. It is of great significance to strengthen the protection of Miyun Reservoir and control the upstream sources pollution, for ensuring the quality and safety of drinking water and the public health and economic development in Beijing.