Distribution Characteristics And Risk Assessment Of Heavy Metals In Farmland Soil Around A Mining Area In Western Inner Mongolia

Soil is an indispensable basic environment and important resource for people’ s survival and development.However,in recent years,with the change of people’ s production activities and various natural environmental reasons,a large number of heavy metals have been entered in the soil,which not only affects the quality of the soil,but also accumulates in the human body through the food chain transmission,and has seriously threatened human health.In this study,the farmland soil around a lead-zinc mining area in the west of Inner Mongolia Autonomous Region was taken as the research object.By collecting topsoil(0-20cm)of the farmland around the mining area,the soil p H,organic matter and the total,effective and toxic leaching contents of six heavy metal elements(Cu,Pb,Zn,Cr,As,Cd)were analyzed and determined.The spatial distribution characteristics of heavy metal elements in farmland soil around the mining area were analyzed by Arc GIS10.7 software.According to the latest released ’ soil environmental quality agricultural land soil pollution risk control standard(trial)’(GB 15618-2018),single factor pollution index method,Nemerow comprehensive pollution index method,geoaccumulation index method and potential ecological risk index method were used to evaluate the pollution status of heavy metals in farmland soil and the risk level of ecological and environmental hazards in the study area.The conclusions are as follows:(1)The content of heavy metals in farmland soil in the study area was as follows: Zn >Pb > Cr > Cu > As > Cd.The average concentration of Cu and Cr did not meet the national standard for soil pollution risk control of agricultural land,but the average concentration of Pb,Zn,as and Cd had exceeded the standard for soil pollution risk control of agricultural land in China.(2)The distribution of Pb,Zn and Cd was relatively similar.Combined with the correlation analysis of these three soil heavy metals,it could be preliminarily determined that there was homology between the soil heavy metals Pb,Zn and Cd in the study area,which might be related to the mining activities of lead-zinc deposits in the study area.(3)A variety of index evaluation methods such as land accumulation index,single factor pollution index,Nemero comprehensive index and Hakanson potential ecological hazard index were constructed to comprehensively evaluate the risk level of soil heavy metal pollution.The results of heavy metal pollution risk assessment showed that the risk of heavy metal Cd was the most serious,followed by Pb and Zn,and the risk of Cu,Cr and As is low.To sum up: the farmland soil in the study area is seriously polluted by heavy metals,and the risk of Cd is the highest.The local government should increase the control of farmland soil heavy metals,especially heavy metals Cd monitoring and risk prevention.