Analysis And Simulation Of Organic Pollution Of Groundwater In A Chemical Plant

Groundwater is a very precious freshwater resource in China,and it is an important foundation for the vigorous development of China's industry and agriculture and the survival of the people.With the rapid development of China's economy and the acceleration of urbanization,the problem of groundwater pollution has become more acute.This paper takes the organic pollutant leakage of a small chemical plant in the north as the research background.Based on data collection in the study area,hydrogeological investigation,field test,groundwater samples are collected and tested for analysis to find out the type and degree of organic pollution of groundwater in the study area.Using the GIS-based DRASTIC model method to evaluate the groundwater vulnerability in the study area,divide the groundwater vulnerability zone,and analyze the anti-pollution capability of the study area.A hydrogeological conceptual model is constructed.On this basis,a groundwater flow model and a solute transport model are respectively established by using the numerical simulation software GMS.Dynamic simulation analysis of the migration and conversion process of carbon tetrachloride,one of the organic pollutants of groundwater,and prediction of the migration path and scope of the pollution plume,providing a scientific basis for the prevention and control of groundwater resources pollution,the protection of groundwater resources and scientific governance.The specific research results are as follows:(1)The test results of 71 groundwater samples in the study area showed that:A total of six organic pollution indicators of carbon tetrachloride,1,2-dichloroethane,trichloroethylene,1,1,2-trichloroethane,tetrachloroethylene,and chloroform were detected.The detection rate of chloroform was the largest,which was 43.66%;the excess rate of carbon tetrachloride was the largest,36.62%,and the maximum over standard multiple was 31349 times.(2)The groundwater samples were evaluated for water quality using the F-value comprehensive index method,and the results showed that:there were 42 excellent water samples,accounting for 59.15%of the total number of samples;as many as 21 poor water samples,accounting for 29.58%of the total number of samples.The results of the water quality evaluation using the Nemero comprehensive index method showed that:42 clean water samples,accounting for 63.38%of the total number of samples;Up to 22 water samples that were seriously contaminated,accounting for 30.99%of the total number of samples;Among the 22 severely polluted water samples,the Nemero Pollution Index P in water sample No.118-2 was the largest,22493.27,which was 4498.65 times the grade factor of the severely polluted water quality.Compared with the F-value comprehensive index method,the Nemero comprehensive index method highlighted the impact and effect of the pollutants with the largest pollution index on environmental quality.(3)Groundwater vulnerability assessment results showed that:The areas with strong vulnerability and strength were mainly distributed in the upper reaches of the chemical plant,mainly because the area belonged to the hilly area in front of the mountain,which was relatively thick in completely weathering,the quaternary sand was relatively thick,the aquifer was highly permeable,and the upper vadose zone was relatively strong in permeability,which was easily affected by the infiltration of surface pollution.The weak vulnerability was mainly distributed on the southwest side of the calculation area,mainly due to the fact that the area was dominated by cohesive soil and the aquifer was weak and thin.(4)Based on the identification and verification of the solute transport model,GMS was used to predict and simulate the diffusion range of carbon tetrachloride contaminated plumes.The simulation results showed that:The migration range of carbon tetrachloride was an ellipse-like pollution area with the leakage point as the off-center and the main water flow direction as the long axis.The concentration of the pollutant at the leakage center was the largest,and the concentration outwards was continuously decreasing;With the passage of time,the pollutant carbon tetrachloride will continue to move along the direction of water flow from northeast to southwest,and cause a certain degree of pollution to the aquifer.By2030,carbon tetrachloride pollution(that is,the range of the three types of water limits)has moved up to 1230m,affecting an area of 2.81×10~5m~2.