Heavy Metal Distribution And Health Risks In Soil Of Tungsten And Rare Earth Mining Areas In Southern Jiangxi

The southern region of Jiangxi is a famous distribution area for tungsten and rare earth mines,known as the"Kingdom of Rare Earths"and the"World Capital of Tungsten."Long-term mining activities have also led to ecological and environmental damage issues,including the destruction of surface vegetation,the discharge of waste（waste water,slag,waste gas,etc.）,ground subsidence in mining areas,and tailings dam breaches.Therefore,the environmental issues generated by mining operations in Jiangxi,especially the trace metal pollution problems brought about by metal mines（heavy metals and rare earth metals）,have attracted much attention.This paper selects agricultural land around the Xihuashan tungsten mine in Dayu County,Zhangjiang River basin,to evaluate the impact of tungsten mines on soil and crops along the Zhangjiang River in a large basin area;selects agricultural land around long-term and short-term tungsten mines in Quannan County as the study area to evaluate the pollution status of heavy metals in farmland soil affected by tungsten mines,and assesses the heavy metal enrichment and potential health risks in major crops;selects agricultural land around rare earth mines in Xunwu County,Xinfeng County,and Longnan City as the study area to evaluate the impact of rare earth mining on soil and navel oranges.The conclusions are as follows:（1）On a basin scale,the main pollutants produced by tungsten mines along the Zhangjiang River basin are As,Cd,Mo,and W.The distribution characteristics of heavy metal pollution areas are obvious,with historical and operating tungsten mine areas along the Zhangjiang River as concentrated pollution areas gradually spreading downstream.The long-term tungsten mining in Dayu County is the reason why the local background value is higher than the Jiangxi Province background value.The accumulation concentration of heavy metals in the soil is ranked as Mo>W>Cd>As>Cu>Pb>Zn>Cr.The most severe heavy metal pollution and ecological risk areas are at the junction of Fujiang Township and Huanglong Town with Qinglong Town.The historical tungsten mine area has extremely high non-carcinogenic risks for Cd,Cu,and Zn in the surrounding soil,and the main carcinogens in local rice are As,Cd,and Cr,posing a very high health hazard in all areas.Tungsten mining has an impact on the soil within the basin area,and the difference in soil property components from the ore composition of the mining area gradually decreases from upstream to downstream near the tungsten mine.Atmospheric dust and wastewater generated by mining activities are the main sources of heavy metals.The soil K₂O and Na₂O are the main factors for the accumulation and migration of heavy metals such as As,Cd,Cu,Mo,Pb,W,and Zn in the soil.Crops have different heavy metal enrichment capabilities in different areas,and rice near the tungsten mine has a strong enrichment effect on Cd.（2）The main pollutants in the soil around the long-mining period tungsten mines in Dajishan are Cd,Pb,Mo,and W,with the source being tungsten mining.The heavy metal concentration in the soil around the short-mining period tungsten mines in Guanshan is lower than that in Dajishan,with the source not only from mining emissions but also from agricultural activities.The soil in Dajishan has reached secondary moderate pollution for Cd,Mo,and W;in Guanshan,the rice soil is moderately to heavily polluted with Cd,Mo,and W,and the vegetable garden soil is moderately polluted.Cd poses the greatest ecological risk,with Dajishan being at high risk and Guanshan at moderate risk.The greatest food safety risk in crops is peanuts,with Cd being the main contributor to the carcinogenicity of crops.The crops in the Dajishan mining area pose a non-carcinogenic risk after consumption,while the food safety risk in the Guanshan mining area is temporarily low.The soil in both long-mining period and short-mining period tungsten mine areas is weakly acidic,and the soil components are similar to the tungsten ore-forming rocks.The heavy metals in the Guanshan mining area mainly come from mining dust,while in the Dajishan mining area,heavy metal pollution is caused by heavy metal leaching due to the influence of water flow on the tailings pond.The enrichment of heavy metals in crops is related to the low biological concentration coefficient,and there is no strong enrichment or hyperaccumulation effect.（3）Rare earth elements（La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,and Y）all exceed the background values of Jiangxi Province in each mining area.The rare earth pollution is greatly related to the type of mining area,mining time,and mining scale.All areas have fractionation of LREE and HREE,with a negative anomaly for Eu,and fractionation of Eu.The potential toxic metals associated with rare earths are distributed differently in different rare earth mining areas,with Pb pollution in Jiading Town and Cd pollution in Guanxi Town.There is no ecological risk for a single rare earth element in the soil,but HREE pollution has already affected the navel orange cultivation in Jiading Town and Guanxi Town.There is no health hazard of rare earths and potential toxic metals in the navel orange fruit.The key factors affecting the accumulation of rare earth elements in navel oranges in the soil around the rare earth mine are K₂O,Fe₂O₃,and SOM.The results of this study provide a scientific basis for improving the management of the impact of mining on agricultural production,propose targeted remediation measures for contaminated soil,and put forward the concept of green mine construction.It provides theoretical guidance for ecological restoration and maintenance in the southern region of Jiangxi.