| Chlorinated hydrocarbons have teratogenic,carcinogenic,and mutagenic effects.After entering the aquifer,chlorinated hydrocarbons will accumulate at the bottom of the aquifer,threatening people’s water for production and living for a long time,causing great harm.The research area was historically an industrial concentration area.The chlorinated hydrocarbon-containing wastewater discharged by industrial enterprises such as chemical industry and chemical fiber during the production process caused serious pollution of chlorinated hydrocarbons in the groundwater of the research area.The pollution needs to be treated urgently.The formation and evolution mechanism of chlorinated hydrocarbon pollution in groundwater system was studied.Under the condition of fully understanding the historical data of the study area,this paper studies the distribution characteristics of chlorinated hydrocarbon pollution in karst water of groundwater system and analyzes groundwater system through hydrogeological survey,water sample analysis,soil sample analysis of vadose zone,numerical simulation,etc.Karst water chlorinated hydrocarbon pollution mode and pollution pathways,etc.use Visual MODFLOW software to simulate karst water chlorinated hydrocarbons in the groundwater system in the study area,predict the chlorinated hydrocarbon pollution plume of karst water in the groundwater system;analyze historical and current water chemistry data,To study the influence of groundwater system,groundwater dynamic field,groundwater chemical field,etc.on the evolution of carbon tetrachloride in karst water of groundwater system.The main results of this research are as follows:(1)Distribution characteristics of chlorinated hydrocarbons in karst water of groundwater system.22 karst water sampling points were set up in the study area.They were sampled and analyzed during dry,wet,and normal water periods.The chlorinated hydrocarbons of karst water in the groundwater system are mainly distributed in B Spring,PJY,and a certain steel plant.The detection rate of chlorinated hydrocarbons in karst water of groundwater system is low,and the detection concentration is high during normal water period.The highest concentration is detected at ZF Village South No.6,and its value is carbon tetrachloride 27.89μɡ/L.(2)Using Visual MODFLOW software,the study area is generalized into a three-dimensional unsteady flow,and parameters are assigned based on the groundwater flow field data.The result is that the model can accurately simulate the flow trend,and the hole water level has a good fitting effect,and its error value the number of points less than 0.5m is more than 75%.Based on the water flow model,MT3D was used to predict the carbon tetrachloride pollution plume of karst water in the groundwater system of the study area after10 years.(3)Chlorinated hydrocarbon pollution model of karst water in groundwater system.According to the distribution characteristics of chlorinated hydrocarbon pollution in the karst water of the groundwater system in the study area,combined with the historical data of chlorinated hydrocarbon pollution in the karst water of the groundwater system in the study area,the main sources of chlorinated hydrocarbon pollution in the karst water of the groundwater system in the study area were determined to be a plastic experimental plant,a petrochemical plant,a chemical plant and so on.The pollution path of chlorinated hydrocarbon in karst water of groundwater system in the study area was analyzed.The pollution path of chlorinated hydrocarbon in karst water in the study area could be divided into direct path and indirect path.Karst water pollution is caused by the chlorinated hydrocarbon wastewater discharged from the pollution sources in the study area entering the karst aquifer through the surface infiltration type,the riverside infiltration type,the overflow type and the seepage pit leaching type,which leads to the karst water pollution.(4)According to the variation of the detected concentration of chlorinated hydrocarbon in the karst water of the groundwater system in 2013,2014,2016 and 2018,the area of chlorinated hydrocarbon pollution plume in the karst water of the groundwater system in the study area decreased from 107km~2in 2013 to 87km~2in 2014 and to 21km~2in 2018.Taking carbon tetrachloride as a typical chlorinated hydrocarbon pollutant in karst water of groundwater system,the concentration of carbon tetrachloride in typical Wells decreases gradually with the passage of time.By analyzing the evolution of carbon tetrachloride pollution in karst water of groundwater system,it can be concluded that the chlorinated hydrocarbon in karst water of groundwater system in the study area is mainly affected by groundwater dynamic field,groundwater chemical field,groundwater system pollution source and other factors,and the concentration of chlorinated hydrocarbon pollution generally shows a downward trend. |
