Heavy Metal Pollution Characteristics And Assessment In Soil Of A Pyrite Plant Production Plant

In this paper,the heavy metals in the pyrite plant production plant soil were studied.The content characteristics of heavy metals were analyzed.Pollution index,enrichment factor and Nemerow integrated pollution index were used to evaluate the pollution status of heavy metals,and the potential ecological risk index and health risk index were used to evaluate the risk caused by heavy metals.The distribution of heavy metals in different forms was studied by BCR extraction test.The bioavailability of heavy metals was evaluated by risk assessment code and ratio of secondary to primary phases.Finally,spatial analysis,correlation analysis,principal component analysis and absolute principal component scoresmultiple linear regression receptor model were used to analyze the sources of soil heavy metals.The results are as follows:(1)In the plant area,the average contents of Pb,As,Cd,Cu,Ni and Hg in the surface soil exceeded the soil background value.The concentration of Pb and As in some sites was greater than the second-class land screening values in GB36600—2018.Except for Ni,heavy metals accumulated on the surface and migrated vertically obviously.The pollution assessment results showed that Hg,As,Cd and Pb were severely enriched and at the serious pollution level,the site as a whole was heavily polluted and at a very strong potential ecological risk.The health risk assessment results showed that As and Pb in the plant soil had noncarcinogenic health risks to adults and children,especially the non-carcinogenic health risks index of As for children was 16.1.(2)Around the plant,the average contents of Co,Cu,Zn,As and Pb in the surface soil exceeded the soil background value.Compared with the filter values of soil pollution in agricultural land,Cu,Zn,As and Pb all exceeded the standard,and As exceeded the most seriously.The element content was related to the direction of the sampling point and the distance from the plant.The pollution assessment results showed that As was the main pollution element,and the soil was heavily polluted and at a strong ecological risk.The pollution level and ecological risk of each region were in the order of northeast > southeast >southwest > northwest.The evaluation results of health risk index showed that As had non-carcinogenic health risks to children,while Cr had carcinogenic risks to children.(3)In the soil around the plant,all the heavy metals mainly existed in the residual fractions,the reducible fractions and the oxidation fractions were in the middle,and the acid-soluble fractions had the lowest proportion.The variation coefficients of all heavy metals in four fractions were large and had strong spatial differentiation.The results of the risk assessment coding method showed that As and Zn were the main pollution elements with low risk on the whole,which may pose a certain threat to the ecosystem.The results of the primary comparison value method of secondary phase showed that Pb and Zn were the main pollution elements,and their bioavailability and environmental risk were high.(4)From the spatial distribution of heavy metals,the heavy metals in plant were mainly distributed in the accumulation areas of raw materials and waste residues.In the plant area,the accumulation of superphosphate raw materials was the main source of Pb and Cd.The accumulation of sulfuric acid raw materials was the main source of Cu and As.The production of sulfuric acid was the main source of Hg,while Ni was produced by factory activities and parent mater ial factors.The high value area of heavy metals was mainly distributed in the area close to the plant.In the soil around the plant,sulfuric acid production was the main source of As,Cu and Co.Superphosphate production was the main source of Zn and Pb,while Cr,V and Ni are mainly from natural sources.The heavy metals in the soil around the plant were mainly from natural sources,and the contribution rate of heavy metals in the soil around the plant was 15.01%.