Distribution Features And Environmental Influence Assessment For Heavy Metals In Soil-maize System From Danzhai-sandu Mercury Mining Area,Guizhou

Danzhai mercury mine is the main mercury mining area in Guizhou,and long-term mining has produced a large amount of tailing.The tailing ponds established in the mining area are limited,and there is still a large amount of mercury tailing accumulated along the slopes around the mining area,and local residents are planting corn on tailing,and whether mercury mine tailing have polluted on the corn with heavy metals is worth further study.In recent years,there have been few researches on heavy metals contamination for soil-crops in Danzhai-Sandu mercury mining area,and further researches are needed on the distribution features of heavy metals in tailing,soil,corns,beneficial elements,and risk(i.e.,health or ecology)assessment.The Danzhai-Sandu mercury mining area as the main research area,invested and tested the collected samples(i.e.,bedrock,tailing,soil,crops)by ICP-MS and ICP-AES.Meanwhile,the value of p H and organic matter of tailing and soil were tested.Combined the element abundance of the upper crust,the soil background value of Guizhou Province,the national soil environmental standards and the national food safety standards,combined with enrichment coefficient,single factor and Nemero pollution index,correlation analysis method,geo-accumulation index,transfer coefficient,enrichment factor,edible corn health risk assessment and other research methods,analyze the distribution of heavy metals,As and Se in soil(tailing)and corn grains in Danzhai-Sandu mercury mining area,pollution status and health risks.The main insights are as follows:1.The mean contents for As,Hg,Sb,Se,Sn and Zn element in tailing are higher than the soil background value for corresponding element of Guizhou Province,and the mean contents for Cd,Cr,Cu,Mo,Ni and Pb element are lower than the soil background value for corresponding element of Guizhou Province.The mean contents for As,Cu,Hg,Mo,Ni,Pb,Sb,Sn,Se and Zn element in tailing soil are higher than the soil background value for corresponding element of Guizhou Province,and the mean contents for Cd and Cr element are lower than the soil background value for corresponding element of Guizhou Province.The mean contents for As,Cu,Hg,Mo,Pb,Sb,Se,Sn and Zn element in soil are higher than the soil background value for corresponding element of Guizhou Province,while the mean contents for Cd,Cr and Ni element are lower than the soil background value for corresponding element of Guizhou Province.2.The mean single factors for As and Hg element in soil are greater than 3,indicating heavy pollution.The mean value of accumulation index for Hg element is greater than 3,indicating very serious pollution.The mean values for As,Hg and Pb element enrichment factor are greater than 3.Dazhai,Wangjiazhai,Gaopai,Paiting,Shuijiawan and Lae have been contaminated by As and Hg.3.The content for Cu,Mo,Se and Zn element in corn grains on the tailing soil is higher than that of the planting soil is lime soil.The contents for As,Cr,Hg and Pb element are all lower than the crop heavy metal limit standards “National Standard for Food Safety Contamination Limits in Food”(GB 2762-2017)and the European Union and WHO/FAO standards.The content of Cu element is lower than the crop heavy metal limit standards “Hygienic Standard for Copper Limits in Food”(GB15199-1994)and WHO/FAO standards.The mean content of Zn element is all lower than the crop heavy metal limit standards “Hygienic Standard for Zinc Limits in Food”(GB 13106-1991)and the WHO/FAO standards.The mean content of Se element in corn grains is higher than “the limit value of Se element in the standard of Eight Elements of Pb,Cr,Cd,Hg,Se,As,Cu and Zn in Grain(including Cereals,Legumes and Tuber)and Products(NY 861-2004)”.The mean values of bioconcentration and transfer factor of harmful elements(i.e.,As,Hg,Pb,Cr and Ni)in corn grains are lower than 1,indicating no enrichment.4.The study found that the corn grown on the tailings of mercury mining area is enriched in the beneficial elements of Cu,Mo,Se and Zn,while the harmful elements(i.e.,As,Cd,Cr,Hg,Ni and Pb)are not enriched.This phenomenon may be resulted in the tailing by adding a large amount of lime powder(adjust the p H),or planting corn soil is lime soil(i.e.,the p H value is weakly acid to weakly alkaline),which inhibits the activation of As,Cd,Cr,Hg,Ni and Pb element,and is beneficial to the activation,migration,and enrichment of Cu,Mo,Se and Zn element in corn grains.This discovery is of great significance to the development of corn rich in Se,Zn and Mo element in this research area.5.Both the ADD values of As,Cd,Cr,Cu,Hg,Ni,Pb and Zn in adult were lower than those of children.The HQ of As,Cd,Cr,Cu,Hg,Ni,Pb and Zn in adults eating corn grains was less than 1,indiciating no health risk.The value of As health risk index(HQ)of corn grains consumed by children was greater than 1,which indicated children should eat less.