Distribution Of Heavy Metals In Various Media In Cadmium Contaminated Mining Areas During Remediation Period And Risk Assessment On Human Health

When a cadmium-contaminated mine site is in a shutdown or remediation period,heavy metals in various environmental media in the area may also pose potential hazards to the surrounding population.In this study,for a cadmium-contaminated mine site during the remediation period,samples of multiple environmental media in the mine site were collected in the field,and the concentrations of heavy metals（Cd,V,Cr,Mn,Co,Ni,Cu,Zn,As,Sb,Ba,Pb）in multiple environmental media（atmospheric PM2.5,dustfall,rice,water）were determined by ICP-MS,and the distribution characteristics of heavy metals in multiple media were analyzed.The biological effectiveness of heavy metals in atmospheric PM2.5（the reference site is Qianhu Campus of Nanchang University）and dustfall samples was evaluated,and the particle size distribution of dustfall was also measured and analyzed,while the health risks of different local populations under multi-media,multi-pathway and multiple heavy metal exposures were quantitatively calculated based on the concentration characteristics of heavy metals in multi-media.The main conclusions are as follows.1.Distribution characteristics of heavy metals in PM2.5（1）The average concentrations of heavy metals in the atmospheric PM2.5 in the mine area and the reference site did not exceed the standard except for As,whose average concentrations were 10.83 ng/m³ and 8.01 ng/m³ respectively,which were higher than the 6ng/m³ stipulated in the Ambient Air Quality Standard（GB3095-2012）.（2）Cd,Cr,Mn,Co,Ni,Cu,Zn,Sb,Ba and Pb in the atmospheric PM2.5 of the mine area are mainly distributed in F1（weak acid extraction state）,V and As are mainly distributed in F2（reducible state）,and Cd,Mn,Co,Ni,Cu,Zn,Sb and Pb have a risk evaluation index>50%and have very high risk,among which the biological effectiveness of Cd is the largest The risk evaluation index of Cd,Mn,Co,Ni,Cu,Zn,Sb and Pb is>50%,with very high risk,among which the biological effectiveness of Cd is the greatest,indicating that Cd is more easily migrated and transformed than other heavy metals,which is harmful to the environment.2.Distribution and particle size of heavy metals in dustfall（1）Compared with the background value of soil in Jiangxi Province,all heavy metals in the dust fall in the mine area are polluted to some extent except Mn,V and Co;compared with the background value of soil in China,all heavy metals are polluted to some extent except Mn,Ba,Cr,V,Ni and Co,among which Cd is the most serious.（2）Cd,Mn,Cu and Zn in the dust fallout of the mine area are mainly distributed in F1（weak acid extraction state）,V,Cr,Co,Ni,As,Sb,Ba and Pb are mainly distributed in F4（residue state）,and the risk evaluation index of Cd,Zn and Mn is>50%,among which the biological effectiveness of Cd is the largest,indicating that Cd is more easily migrated and transformed than other heavy metals and is more harmful to the environment.（3）The particle size of dustfall in the mining area is mainly distributed in0～2.5μm,accounting for 60.87～78.48%,the particles above 10μm are less,the overall distribution of dustfall particle size is the same,and the particle size is obviously smaller;the characteristic distribution range of indoor dustfall and atmospheric dustfall at different distances Similar,the particle size is mainly distributed in 0～2.5μm;the characteristic distribution range of particle size of the dust falling at the same distance is similar,and the particle size is mainly distributed in 0～2.5μm.3.The distribution characteristics of heavy metals in rice and drinking water samples（1）The concentrations of 12 heavy metals（Cd,Pb,As,Cr,Mn,Cu,Zn,V,Co,Ni,Sb,Ba）in rice from the mine area were in the range of 0～15.846 mg-kg^-1,and compared with the limit values of"the National Food Safety Standards for Contaminants in Food"（GB2762-2017）,the rice samples all met the standard values;the concentrations of 12 heavy metals in the drinking water samples were in the range of 0～220.157μg·L^-1 and compared with the limits of the"Sanitation Standards for Drinking Water"（GB5749-2006）,the drinking water samples in the mining area（well Water,tap water）are in line with the standard value;through the analysis of the excess rate,the concentration of heavy metals in the rice and water samples in the mining area did not exceed the standard.（2）The content of Cd and Cr in rice from the mining area was at a medium to high level,and other elements were at a medium to low level,with the content of Cd higher than that in Suzhou,Beijing supermarket and Ningxia,but lower than that in the electronic waste factory in Qingyuan City,Guangdong Province and a mining area in Guangxi Province,which may be related to the fact that the sampling area is located around the mining area and the rice samples were contaminated with certain heavy metals.4.Heavy metal exposure and risk assessment on human health in the study area.（1）The total non-carcinogenic risk of 12 heavy metals for the population in the mining area was Mn>As>Cr>Cd>Co>Sb>Cu>Zn>Pb>V>Ba>Ni,and the ranking of the total non-carcinogenic heavy metal risk for different populations was consistent,with children（5-5 years old）>adult women>adult men,in which the HQ values of total non-carcinogenic risk for Mn,As and Cr were>1.Except for Mn,Ba,As,Cr and Ni,the contribution rate of total non-carcinogenic exposure to heavy metals was the highest:oral intake>dermal contact>respiratory inhalation.（2）The total carcinogenic risk of the five carcinogenic heavy metals in the mine population was As>Cd>Cr>Co>Ni,and the risk ranking of the total carcinogenic heavy metals in different populations was consistent,with children（5-6years old）<adult males<adult females,and the highest carcinogenic contribution rate from oral intake,and the total carcinogenic contribution rates of the five carcinogenic heavy metals except Cr and Ni were:oral intake>dermal exposure>respiratory inhalation.The total carcinogenic exposure of As is greater than 10^-4,and the total carcinogenic exposure of Cd is at the critical value of 10^-4 for children（5-6years old）and high risk for adult males and females,while the total carcinogenic exposure of Cr is at the critical value of 10^-4,which is at the level of medium carcinogenic risk.