Ecological Risk Assessment Of Heavy Metals In Sulfide Mining Area Of Shuikoushan,Hunan

The remote-sensing interpretation work in Shuikoushan area shows that there are many typical mining targets in this region,and the acid mine drainage(AMD)affects the water,soil and crops in the surrounding environment.In order to assess the ecological risk caused by the mining target and monitor the heavy metal water-soil movement process in the mining area,the heavy metal flux model and rice absorption model are established based on the water and stream sediment sample data collected by the mining area target,as well as the monitoring sampling point data set up in the upstream and downstream of the mining area watershed.The results show that the heavy metal net of the research area watershed is high and the pollution of agricultural land and crops is serious.Based on the study of the geochemical characteristics of AMD and its stream sediment,it is found that the mineral processing has an important influence on the pH value and heavy metal speciation distribution of tailings seepage: the seepage pH of wet tailing pond is significantly higher than that of dry tailing pond,and Cd in the former stream sediment tends to exist in the form of residue,while most of Cd in the latter stream sediment is in the form of water-soluble and ion-exchangeable.The analysis of solid-liquid partition coefficient of heavy metals also shows that the partition coefficient of most heavy metals has a significant positive correlation with pH value.According to the estimation of heavy metal flux model in the study area,the net flux of heavy metals,especially Cd and Cu,is relatively high,which leads to high ecological risk.However,the evaluation results of rice and root soil show that agricultural land and crops in the study area are seriously polluted by heavy metals.Combined with the rice absorption model and the estimated heavy metal flux in the watershed,it is predicted that if strict control measures are not taken,large-scale food security problems will occur in the study area.According to the data of monitoring sampling points set up in the upstream and downstream of the mining area watershed,the total concentration of suspended solids in the water sample will increase after passing through the mining area watershed,and rainfall activities will significantly increase the concentration of suspended solids in the downstream,thus breaking the dissolved-suspended equilibrium in the water body,further affecting the solid-liquid distribution of heavy metals.