Risk Assessment And Simulation Of Heavy Metals Of Industrial Polluted Soil In Xuzhou City

Heavy metals come from a wide range of sources,exist in various forms,have complex migration and transformation principles.At present,China's industrial enterprises are developing rapidly.Some industrial enterprises may have imperfect management systems,relatively backward technologies,and low efficiency of high-efficiency recycling.This could cause a large amount of heavy metal pollutants to enter the soil environment and a series of environmental pollution problems,and is harmful to human health.In this study,the soil in factory A,B,C and D in Xuzhou City were selected as research objects.The combination of field survey sampling,laboratory experiment,data analysis and model simulation was used to carry out risk assessment and simulation of heavy metals in industrial polluted soil in Xuzhou City.The results are as follows:(1)Based on descriptive statistical analysis,it is found that heavy metals such a s Cu,Pb,Zn,Ni,Cd and As are accumulated in different degrees in the study area.Compared with the Screening Values of Standards for Risk Control of Agricultural Soil Pollution(GB15618-2018),the heavy metal Cd in the study area has exceeded the standard.The variability degree of heavy metal content in soil with different soil depth is different.The content of Cu and Hg is more likely to decrease with the increase of soil depth.The content of Zn in soil is the highest when the depth of soil layer is 0.5-1.0m.The content of Pb and Cd in soil increases with the increase of soil depth.The distribution of heavy metal Ni and Cr contents in different soil depths shows that 0.5~1.0m< 4.5~6.0m< 2.5~3.0m.The distribution of heavy metal As content in different soil depths shows that4.5~6.0m<0.5~1.0m<2.5~3.0m(2)Based on Kriging interpolation and correlation analysis,it is concluded that the accumulation of heavy metal in soil is probably related to the production activities of industrial enterprises.The order of average contents of Cu and Ni in different sites is C > A > B > D.The order of the average contents of Pb,Zn and Cr is A > C > B > D.The order of the average content of Hg is D > A > B > C.The order of the average content of As is A > B > C > D.The order of the average content of Cd is B > C > D > A.The correlation coefficients of Cu-Ni(0.523),Cu-Cr(0.577),Pb-Ni(0.685),Ni-Cr(0.656)and Ni-As(0.556)are relatively large.They may come from similar sources.(3)Based on the evaluation of index method,it is found that the average single pollution index of heavy metal Cd in soil in the study area is more than 1.0,which is at a slight pollution level,and other heavy metal elements are at a safe level.The average nemerow comprehensive pollution index of soil heavy metal is 0.85,and the overall situation of soil is above the alert limit(still clean)level.However,the number of samples with mild pollution in the study area accounted for 25.64%,and the warning limit and safety level accounted for 74.36%.This shows that the degree of soil pollution shows a warning limit-mild pollution level.(4)Based on the human health risk assessment method,the order of non-carcinogenic risk of through two exposure routes is Cu > Zn.Oral exposure route is an important source of contribution.The order of non-carcinogenic risk through three exposure pathways is As > Cr > Ni > Cd > Hg.The order of carcinogenic risk is Cr > As.The carcinogenic risk caused by Cr and As are acceptable.The total non-carcinogenic health risk and total cancer risk risk caused by heavy metal elements in the soil of A are the most serious.The C plant area is the second,and the D plant area is the lightest.(5)Based on the flow model and solute transport model,it is concluded that with the increase of soil depth,the migration rate of pollutants tends to decrease,and the concentration of pollutants decreases with the increase of soil depth.Although the soil has a certain adsorption and filtration capacity for pollutants,it can only intercept the pollutants to some extent.With the increase of the migration time of heavy metal pollutants,it may pollute the underground water.