三峡库区典型排污口河段污染物扩散降解特性研究

Study on characteristics of contaminant diffusion and degradation of typical river section in the Three Gorges Reservoir Area

为减轻三峡库区长寿—涪陵段水环境污染,改善区域水质,建立了以水动力-水质模型为基础的区域关键排污口的筛选分析方法。采用三维数值模型EFDC对研究区域内污染物的超标面积进行模拟计算,并对污染物扩散降解特性进行分析,利用单位污染物负荷超标面积分析不同排污口污染物迁移扩散的差异,进行流域重点排污口的分析筛选。从改善整体河流水质出发,分析了各排污口位置的合理性。结果表明,支流回水区内排污口的混合区面积比干流河段处排污口要大,顺直江段处的排污口的混合区面积较弯段内侧处排污口要小。排污口应选在流速和水深较大的顺直河段,避免选择支流回水区。

To improve water quality and alleviate pollution in Changshou-Fuling section of the Three Gorges Reservoir Area,an analytical methodology for screening the regional key discharge outlets based on hydrodynamic-water quality model was developed.A three-dimensional numerical model,EFDC （Environmental Fluid Dynamics Code）,was used to study the impact of different discharge outlets on the transport of contamination in the studied area.The EFDC model calibration was conducted by using observed data collected in 2008.The results indicated that the model has well simulated the variables,with the majority of relative errors being less than 25%.The EFDC model is able to perfectly simulate the hydrodynamic characteristics and contaminant transport process.Through the mathematical model,the calculated pollutanlogt mixing zone can be used for the screening of regional key discharge outlets.An analysis on the spreading characteristics of pollutanlogts in different discharge outlets was carried out by using the method of pollutanlogt mixing zone per unit load.The rationality of the locations of discharge outlets were analyzed from the perspective of river water quality protection.The results showed that the locations of discharge outlets in Fuling are more reasonable than those in Changshou.Pollutanlogt mixing zone of the discharge outlets in the tributary of the backwater area are larger than the discharge outlets in the main stream of the river.Pollutanlogt mixing zone of the discharge outlets at straight section of the river is smaller than the discharge outlet at curved section of the river.The discharge outlets should be located at the straight section of the river with greater velocity and depth,in order to avoid exemption tributaries recirculation zone.Pollutanlogt mixing zone per unit load can be served as the basis of discharge outlet load reduction and control selection.This study provides useful information for the optimization of discharge outlet location and prediction of pollutanlogt mixing zone in the studied area,which are importanlogt for the planning of water pollution control measures.