Urban Surface Runoff Organic Pollutants Characteristics And Migration Of Typical Pollutant In Rainwater Infiltration Medias

In this study,the volatile organic compounds(VOCs)and semi-volatile organic compounds(SVOCs)in runoff from 6 different functional areas of Daxing District suburb,Beijing were investigated,and the pollution levels,distribution characteristics and possible sources of VOCs and SVOCs were analyzed.On the basis of above analysis a typical volatile organic compound-methyl tert-butyl ether(MTBE)was selected,then migration and residual characteristics of MTBE in the common fillers of the sponge city facilities were studied by simulated column experiments,including the effect of concentration,pH and flow velocity on the migration of MTBE,so as to provide scientific basis for prevention and control of urban runoff and the treatment of VOCs in the construction of sponge cities.The results indicated that 46 species VOCs were detected in 36 runoff samples from six land use sites in Daxing District,Beijing,including 25 benzene series,20 PAHs and MTBE,of which 15 species VOCs were detected in all runoff samples;meanwhile 72 SVOCs were detected,including 24 benzene series,24 PAHs,6 PAEs,10 pesticides and drugs,3 PCBs and 5 other SVOCs,of which 27 SVOCs were detected in all runoff samples.ANOVA results shows that both land use types and rainfall time may have significant effects on the change of VOCs in runoff.The concentration of VOCs and SVOCs in runoff varies with the location,and the change is influenced by the factors such as rainfall intensity,rainfall,runoff variatio,catchment area,road dust and so on.VOCs and SVOCs in runoff mainly come from pollutants accumulated on road surfaces,partly from rainfall.BTEX and halogenated aromatics mostly come from the chemical plant;MTBE mainly comes from gasoline emissions,spills and vehicle exhausts;and the main sources of the PAHs pollution is the accumulation of the burning source and the oil source on the land surfaces;PAEs mainly come from the accumulation of the plastic products on the surface particles;pesticides and drugs mainly come from pesticides attached to green plants and soil;PCB and other SVOCs can be considered as sources of factories or other chemical behaviors.The results of the column experiment show that the migration ability of MTBE in the medium is inversely proportional to the depth of the medium,whereas the residual amount is proportional to the depth,which indicating that the MTBE will migrate downward with the runoff,and there is a potential pollution risk to the groundwater.The migration ability of MTBE in soil is weaker than medium sand but the residue is higher.Soil organic matter and clay content may be the cause of the difference.The increase of leachate concentration and flow velocity will promote the migration rate of MTBE,reduce the residual of MTBE in the medium,strengthen its downward migration ability and move more quickly to the deep underground,but the change of the percolation pH has little effect on the migration and residue of MTBE.