Spatial Distribution And Health Risk Assessment Of Heavy Metals In A Mining Area

This paper takes a mining area in Chenzhou City,Hunan Province as the research object,the cumulative characteristics,spatial distribution characteristics,pollution assessment and human health risk assessment of the content of Pb,Zn,Cd,Cu in the soil of the mining area and each functional area,the main pollution sources and the contribution rate of each pollution source were studied.Use Surpac and Matlab software to obtain the spatial distribution map of heavy metal content accumulation,pollution and human health risks.The main results of the study are as follows:1)The descriptive statistics of heavy metals in soils of the mining areas by classical statistical methods show that:the average content of heavy metals is Zn(265.3 mg.kg^-1)>Pb(138.13 mg.kg^-1)>Cu(99.61 mg.kg^-1)>Cd(1.00 mg.kg^-1).The average contents of Pb,Zn,Cd and Cu are 4.67,2.90,9.43 and 4.08 times of the Hunan soil background values,respectively,and the influence factors are Cd>Pb>Cu>Zn,indicating that the mining area has significant influence on the enrichment of Pb,Zn,Cd and Cu in the surrounding soil in the process of mining and smelting of high-strength mineral resources for many years.The uneven distribution of the average contents of Pb,Zn,Cd and Cu in the soil indicated that different production activities have different effects on the accumulation of heavy metals in the soil.2)Through improved Nemero pollution index method,potential ecological hazard index method,environmental risk method and analytic hierarchy process?AHP?method,the pollution and hazard risk assessment of heavy metals in mining areas and functional areas is carried out.The results showed that:Cd in the soil of the mining area was at a serious pollution level,with the largest contribution to pollution,and should be treated with priority.Pb and Cu are moderately polluted,and Zn is slightly polluted;Pb,Zn,Cd and Cu in the soil of each functional area are at a moderate or severe pollution level;the comprehensive pollution level of heavy metals in the soil of the mining area and each functional area is severe pollution.The single-factor potential ecological hazard index in the mining area is Cd?1404.32?>Pb?23.33?>Cu?20.41?>Zn?2.90?.Cd presents a strong potential ecological hazard,while Pb,Zn and Cu showed slight potential ecological hazard.The value of soil heavy metals in each functional area is greater than 200,which has a extremely strong potential ecological hazard.Cd is the most important contributing factor.Among the environmental risks of the soil in the functional areas of the mining area,there are extremely high environmental risks in the tailings area,high environmental risks in the traffic road area,and medium environmental risks in the mining area,residential area and planting area.Cu is the biggest factor causing high environmental risk in mining soil,followed by Pb and Zn.3)By applying the health risk model of polluted sites in China and the human exposure risk model of USEPA,relevant parameters suitable for China are selected to evaluate the human health risk in mining areas.The results show that:there is carcinogenic risk of Cd in mining areas,and oral ingestion is the main exposure route.Targeted measures should be taken to prevent it.Pb and Cd are the main non-carcinogenic risk factors in the mining area,but both the HQ value and HI value are less than 1,which does not exceed the acceptable risk range,indicating that there is no non-carcinogenic risk in the mining area.4)According to the spatial distribution of heavy metal content and pollution risk in the mining area,the results showed that:Pb,Zn,Cd and Cu contents and pollution risk coefficients peak in the central and eastern area?the intersection of tailings area and road traffic area?,the most serious pollution.On the basis of understanding the spatial distribution characteristics of heavy metal pollution in mining area,correlation analysis,cluster analysis,principal component analysis and PMF model analysis were used to analyze the source of heavy metals in the mine soil.The results show that:there is a compound pollution of heavy metals in mining area.Tailings accumulation is the main source of Pb,Zn and Cd in the mining area,and its source contributions rate is 70.633%;the main pollution sources of Pb,Zn,Cd and Cu in the soil are:agricultural sources,transportation sources and industrial sources.