库区面源氮、磷污染对于桥水库水质的影响

Effects of non-point source pollution of nitrogen and phosphorus on water quality of the Yuqiao Reservoir

于桥水库作为天津市唯一的饮用水供水水源地,研究于桥水库周边面源污染对其水质的影响,有助于改善水库水环境,保障供水质量。在分析水库周边面源污染负荷的基础上,运用基于二维浅水方程和对流扩散方程组构建的于桥水库二维水动力和水质耦合模拟模型对2008年雨季(6月-9月)水库TN、TP浓度的空间分布及随时间变化特征进行了模拟分析。结果表明,受果河入库流量和汛期主导风的影响,总体上TN、TP随水流主要沿水库南岸和西北岸向坝前方向扩散,并在库区东形成顺时针大环流和在库区西形成逆时针环流。受环流影响,库心水质受污染影响较小。TP在空间上呈现出东高西低的趋势,TP平均浓度最高值出现在8月份为1.56mg/L;刘相营及五百户镇是TN的主要入库口,TN平均浓度最高值出现在9月份为3.74mg/L。

Yuqiao Reservoir is the unique water source for the water supply of Tianjin City. It＇s important to study the effects of the non-point pollution around Yuqiao Reservoir on the water quality in order to improve the water environment and guarantee quality of water supply. Based on the analysis of non-point pollution load, a coupled two-dimensional hydrodynamic and pollutant transport model was developed using the two-dimensional shallow water and pollutant transport equations. The two-dimensional model was used to simulate the temporal and spatial distribution characteristics of TN and TP in the reservoir water from June to September in 2008. The simulation results showed that（1） under the effects of inflow of Guo River and dominant wind direction in the wet period, TN and TP concentrations diffuse towards the dam site along the south and northwest coastlines, and form the clockwise circumfluence in the east area and the counterclockwise circumfluence in the west area of the reservoir; （2） due to circulation, the water quality in the reservoir center is less affected by the pollution; （3）TP concentration in the east is higher than that in the west of the reservoir,and the average concentration of TP in August is the highest（1.56 mg/L） ;and（4） I.iuxiangying and Wubaihu are the main pollution ports of TN, and the average concentration of the TN in September is the highest（3.74 mg/L）.