北运河上游非点源污染负荷模拟与最佳管理措施评估研究

Simulation of Non-Point Source Pollution Load and Evaluation of Best Management Practices in the Upper Beiyun River Watershed

非点源污染是水污染的重要来源之一,揭示非点源污染负荷空间分布特征、筛选并布设最佳管理措施(best management practices,BMPs)对水污染的高效治理有至关重要的意义.北运河作为北京市重要的排水通道和连接京津冀的重要生态走廊,加强北运河上游非点源污染治理对北运河流域的水质改善至关重要.然而,当前缺乏针对非点源污染关键源区内布设不同BMPs生态效益评价的研究.因此,为了解析北运河上游非点源污染空间分布特征,评估关键源区布设不同措施的生态效益,本文基于SWAT模型定量模拟了2019年北运河上游总氮、总磷负荷空间分布特征,并采用单位负荷指数法识别了非点源污染关键源区,同时评估了关键源区布设不同BMPs的总氮、总磷削减效果.结果表明:(1)2019年北运河上游流域产生的总氮、总磷负荷分别为126444.22和12394.76 kg,呈东南高西北低的空间分布特征,主要来源于城镇用地、耕地和果园等地类.(2)北运河上游关键源区分布在东南部17条子流域,占流域总面积的13.16%,产生的总氮、总磷负荷分别占全流域的39.16%和38.10%.(3)1/5面积比植被缓冲带的总氮、总磷削减率最高,分别为38.20%和40.37%;2 km河道植草的总氮、总磷削减率最高,分别为19.47%和50.90%;由于关键源区范围内农地面积较小(9.62%),化肥减施措施下污染物削减较低.研究显示,非点源污染关键源区主要分布在人类活动较多的流域东南部,可通过布设合适的植被缓冲带和河道植草措施,降低关键源区非点源污染负荷.

Non-point source pollution is one of the major sources of water pollution.Revealing spatio-temporal distribution characteristics of non-point source pollution load and screening and layout of best management practices(BMPs)is vital for efficient water pollution treatment.As an important drainage channel in Beijing and an important ecological corridor connecting Beijing,Tianjin and Hebei,strengthening the control of non-point source pollution in the upper Beiyun River is crucial to the improvement of water quality in the Beiyun River watershed.However,there is a lack of research on ecological benefit evaluation of different BMPs in critical source areas(CSAs)of non-point source pollution.Therefore,in order to analyze the spatial distribution characteristics of non-point source pollution in the upper Beiyun River Watershed and evaluate the ecological benefits of different BMPs in the CSAs,the SWAT Model was used to quantitatively simulates the spatial distribution characteristics of total nitrogen(TN)and total phosphorus(TP)loads in the upper Beiyun River in 2019,and the unit load index method was used to identify the CSAs,and the TN and TP reduction effects of different BMPs in the CSAs were evaluated.The results showed that:(1)In 2019,the TN and TP loads in the watershed were 126,444.22 and 12,394.76 kg,respectively,with high values in the southeast and low in the northwest,and the TN and TP loads mainly come from urban land,cultivated land,and orchard.(2)Seventeen sub-watersheds were identified as CSAs,accounting for 13.16%of the total area of the watershed,and the TN and TP loads generated from the CSAs accounted for 39.16%and 38.10%of the watershed,respectively.(3)The reduction rates of TN and TP for 1/5 area ratio filter strip were the highest,38.20%and 40.37%,respectively;the reduction rates of TN and TP in 2 km grassed waterway were the highest,which were 19.47%and 50.90%respectively;As the area of agricultural land within the CSAs is small(9.62%),the pollutant reduction rates for the chemical fertilizer reduction measures are relatively low.The results show that the CSAs for non-point source pollution is mainly distributed in the southeast of the basin with intense human activities.The non-point source pollution loads in the CSAs can be reduced by appropriate implementation of filter strip and grassed waterway.