Research On The Influence Of Rainwater Biological Filter Setting Conditions On Heavy Metal Species And Microbial Diversity

With the gradual control of point source pollution in China,the contribution of non-point source pollution to water environment pollution has exceeded that of point source pollution,so solving non-point source pollution has become the top priority of water environment governance.The heavy metal pollutants in urban runoff pollution have the characteristics of easy migration and great harm,which deserves extensive attention.In order to solve urban non-point source pollution,our country puts forward the concept of building a "sponge city" with low-impact development as the core concept.As a typical low-impact development technology,rainwater biofilter has been widely used in the world.However,the ability of the rainwater biofilter to treat urban runoff will gradually weaken with the continuous influx of runoff containing heavy metals,and the heavy metals trapped in the rainwater biofilter also have the risk of precipitation,which will further harm the urban surface water environment.Many scholars at home and abroad have conducted research on the influence of the macroscopic setting conditions of the rainwater biofilter on the removal rate of heavy metals,and have achieved many results.Based on this,this study investigates the difference of heavy metal removal efficiency of the rainwater biofilter and the responsive mechanism of micro-environment under two macroscopic conditions(with or without submerged area setting,with or without reed planting)by measuring the distribution of heavy metals in the rainwater biofilter and the microbial diversity,in order to explore the method that can solidify the heavy metals in urban runoff in the rainwater biofilter to the maximum extent.This study sets up two variables,setting the submerged area or not and planting reeds or not,and conducted the intersecting test.Through the analysis of the removal efficiency of Pb,Cd,Cu,Cr these four heavy metals,the element distribution of heavy metals,and the growth of microbial flora in eight rainwater biofliters under four setting conditions,the following conclusions are obtained:(1)Planting reeds has a major effect on removing the four heavy metals,which enhances the removal efficiency of four heavy metals.The setting of the submerged area has an impact on the removal of heavy metals,but the impact is lower than that of reed planting.(2)Under the condition of planting reeds,the content of weak acid soluble state of the four heavy metals is lower than that without reed planting,but the residual state shows the opposite.The heavy metals are more easily intercepted by the packing,and the removal efficiency of the device is higher.(3)The change of the relative abundance of the dominant flora that has a significant positive correlation with the heavy metal removal rate under different macro-control conditions is consistent with the change of the value of the heavy metal removal rate.The experimental results can provide data support for the optimal design of rainwater biofilter,which is of great significance for improving the ecological environment,increasing economic and social benefits,and realizing resource allocation and sustainable development.