Characteristics And Risk Assessment Of Heavy Metal Pollution In Farmland Soil Of Linfen City

In this paper,247 soil samples were collected from Linfen city(Yaodu district,Xiangning county,Huozhou city,Yicheng county,Hongtong county and Quwo county),and the contents of Cd,Cr,As,Hg,Pb,Cu,Zn and Ni in soil were determined to study their content characteristics and spatial distribution.In this paper,pollution assessment,ecological risk assessment and health risk assessment of heavy metals were carried out.(1)The results of soil heavy metal content characteristics show that the content distribution of Cd,As and Hg accords with normal distribution,while the content distribution of other five heavy metal elements shows different degrees of peak deviation.At the same time,it is found that the coefficient of variation of Cr and As is small,the coefficient of variation of Hg is large,and the variation of other metals is in the middle.(2)By analyzing the spatial distribution characteristics of heavy metals,it is found that the high-value areas of Cd,Cr,As,Pb,Zn and Ni are concentrated,which are related to soil-forming parent materials and natural factors.However,the pollution of spot distribution and extremely high-value spot distribution can not be separated from the intervention of human activities,mainly due to transportation,mining,industrial production,unreasonable application of chemical fertilizers,etc.(3)Principal component analysis shows that the first four principal components can explain 82.438%of the information of the sample,and Cr,Pb,Zn and Ni have higher loads in first principal component,As in the second principal component,Cu in the third principal component and Hg in the fourth principal component.Through cluster analysis,the heavy metal elements in soil are divided into four categories,the first category is Pb,Zn,Ni,Cr and Hg,which represent the sources of polluting enterprises such as coal;The second type is Cu,which represents the source of soil-forming parent material;The third category is As,which represents the source of industrial emissions;The fourth category is Cd,which represents the source of irrational application of chemical fertilizer.(4)By analyzing the single factor index evaluation method,taking the soil background value of Shanxi Province as the evaluation standard,the average single factor index of heavy metals in the study area is Hg(4.81)>Pb(1.87)>Cu(1.33)>Zn(1.22)>As(1.21)>Cd(1.15)>Cr(1.08)>Ni(0.87).According to the risk screening value in GB 15618-2018,the average single factor index of heavy metals in the study area is as As(0.44)>Cu(0.31)>Zn(0.26)>Cr(0.24)>Cd(0.20)>Pb(0.16)>Ni(0.14)>Hg(0.03).Taking the soil background value of Shanxi Province as the evaluation standard,nearly half of the villages in the study area were seriously polluted.Taking the risk screening value as the evaluation standard,the Nemerow comprehensive pollution index of only one sample is 1.73,which is much higher than other samples.The Nemerow comprehensive pollution index of other soil samples is less than 0.7,which is within the warning line.The geoaccumulation index method is evaluated with reference.The evaluation results of geoaccumulation index show that the pollution degree of heavy metals in farmland soil in the study area is Cr>Hg>Pb>Cu>As>Zn>Cd>Ni from strong to weak,and the pollution degree in the study area is generally from non-pollution to moderate pollution.(5)The potential ecological risk assessment method was carried out according to the background value of soil environment in Shanxi Province.The results showed that the ecological damage degree of eight heavy metal elements from strong to weak was Hg>Cd>As> Pb >Cu>Ni>Cr>Zn.(6)Evaluate the carcinogenic risks of Cd,Cr,As and Ni.The results showed that the average carcinogenic risk index of Cd and As elements was less than 10-4,and the carcinogenic risk was within the controllable range.The average carcinogenic risk index of Cr and Ni is greater than 10-4,and there is carcinogenic risk.The results of non-carcinogenic risk assessment show that the non-carcinogenic risk indexes of eight heavy metals are all less than 1,which is less harmful to human body.