Study On The Migration Law Of Dense Non-aqueous Phase Liquids Pollutants

The water source of Qiligou in Xuzhou City guarantees more than 200 thousand peoplein the southern part of the city.According to the monitoring data,the Qiligou karst water source has been contaminated by carbon tetrachloride since 2000.The pollution source is located in the pesticide west plant in the southwest of the water source,and the long-distance migration of carbon tetrachloride has polluted the underground water in the urban area.As a typical dense non-aqueous phase liquids（DNAPLs）carbon tetrachloride is highly polluting soil and groundwater,which poses great harm to human health and production environment.Based on the carbon tetrachloride pollution of karst groundwater in Xuzhou City,this paper studies the solute transport law of groundwater in Qiligou karst aquifer,and establishes the theoretical model of dnapl in groundwater migration and the pollution of carbon tetrachloride in Xuzhou City.The numerical model predicts the future pollution status of carbon tetrachloride.The main research contents are as follows:（1）Analyze the effects of climatic conditions,types of aquifer media,karst occurrence characteristics,groundwater flow field and artificial mining activities on the spatial distribution and dynamic change of carbon tetrachloride in karst water in the study area.（2）Study the theoretical model of DNAPL in groundwater migration.Through the properties and migration mechanism of DNAPL pollutants,the three-phase flow migration model of carbon tetrachloride in the study area was established by Petrasim software.The moving three-phase flow system changes under the infiltration condition in the unsaturated zone,and the residual phase formed in the soil will continue to enter the karst aquifer under the action of gravity.（3）Study the migration law of carbon tetrachloride in karst water,and establish the hydrogeological conceptual model and groundwater flow in the study area by analyzing the regional geological,hydrogeological conditions and water flow dynamics of the study area.Two-dimensional model of water quality.The feflow software based on the finite element method was used to solve the model.The water level and carbon tetrachloride concentration contours in December 2012 were used as the initial water level and background concentration to simulate the concentration of carbon tetrachloride pollution plumes in groundwater field,The seepage field of groundwater in December 2014,December 2016,December 2018 and December 2020 and the variation field of carbon tetrachloride concentration are predicted.The results show that the concentration of carbon tetrachloride in the whole research area shows a decreasing trend,and the attenuation trend in the northern and southern areas is obvious.The attenuation of the double dumbbells of the pollution plume decreases with time,and the concentration of“dumbbell”in the north decreases obviously.The pollution plume gradually changed from“double dumbbells”to“single dumbbells”.The results of this paper show that the control project of CCl₄pollution source has achieved satisfactory results in recent years.The paper has 33 pictures,11 tables,and 89 references.