| Currently our country has raised water environmental governance to the national strategic position,and urban point source pollution was the first to get effective governance,meanwhile water environment has been improved significantly.However,the water quality of urban water decreased significantly after rainfall.The main reason is that the urban surface carries a large number of pollutants in the process of rainfall runoff,which worsens the quality of receiving water.Thus based on the basic theory and experiment of urban rainfall runoff pollution,taking the characteristics of FX and ZKS during rainfall in PS River Basin as an example,study the characteristics of rainfall runoff pollution in an area of Shenzhen city.In order to explore the regional characteristics between different tributaries,four typical pollutants,COD,NH3-N,TP and SS were selected and the method of manual sampling on site was used to study the regional rainfall and runoff pollution rules,the correlation between pollutants,pollution load and initial scour effect.The specific research results are as follows.First,the study on rainfall-runoff pollution process and correlation shows that:The COD,TP and SS concentrations of rainfall runoff in the FX area and the upper reaches of ZKS area were high in the initial rainfall period,and gradually decreased with the runoff time in the middle and later periods.NH3-N concentration in the FX area was consistent with the above changes,but the curve of NH3-N concentration in the upstream area of ZKS showed an upward parabola with the opening over time.（2）From the analysis of characteristics of instantaneous concentration of rainfall-runoff pollution,it can be seen that:（1）The maximum instantaneous concentration of COD,NH3-N,TP and SS in the two study areas appeared in the rainfall field with the longest drying time in the early stage.（2）The average values of COD,NH3-N,TP and SS in each field in FX region are 105.00mg/L,6.27mg/L,1.12mg/L and55.65mg/L.The average values of COD,NH3-N,TP and SS in each field in ZKS region are 49.68mg/L,0.23mg/L,0.59mg/L and 60.94mg/L,which are higher than that in ZKS region.（3）The maximum standard deviation and coefficient of variation of instantaneous concentration in the two study areas are large,which indicates that the instantaneous concentration distribution is relatively discrete and the concentration variation range is wide,so it is not suitable to choose the arithmetic mean as the representative value of rainfall-runoff pollution.（3）Taking the region as a unit,there is a strong correlation between COD,SS and TP in the two regions,while there is no correlation between NH3-N and COD,SS and TP,so there is no explanatory power between NH3-N and other indicators in the study region.Taking rainfall events as a unit,the regression analysis shows that the correlation between SS and COD is stable in FX region,and there is a correlation between SS,COD and TP in each rainfall of ZKS,and there is mutual explanatory power among them.Second,the study on rainfall runoff pollution intensity and load shows that:（1）SS and COD are both the main pollutants in the two areas,and the average pollution concentration in FX is higher than ZKS,which exceeds the class V water limit specified in the water quality standard.（2）According to the average concentration load estimation method,the pollution load in the FX area is much greater than that in the ZKS area,with an order of magnitude difference and serious pollution.The calculation of each field load by unit area load estimation method shows that COD,TP,and SS in ZKS area on unit area pollution area is more serious than that in FX,but the content of NH3-N is below class Ⅲ water limit.Thirdly,the study on the initial scouring effect of rainfall runoff shows that:The total intercepted pollution loads of 40%runoff volume at the initial stage in FX region and ZKS region are 39.57%-43.71%and 51.77%-53.23%respectively.The end closure in FX region will not achieve the expected effect,and 40%of the closure in ZKS region can effectively remove most pollutants generated by rainfall scouring. |
PDF Full Text Request