Leaching Characteristics And Ecological Risk Assessment Of Heavy Metals In Typical Tailings Around Lhasa

The exploitation of mineral resources makes a large amount of tailings waste.Tailings is rich in a variety of heavy metals,after natural precipitation,human activities and other influences,tailings in the heavy metals into the environment,causing a huge impact on the environment,tailings has also become one of the main sources of heavy metal pollutants in the environment.Therefore,tailings waste has also become an important factor directly or indirectly affecting human health and the quality of the natural environment.Due to the natural geological advantages,the mineralization conditions in the Tibet Autonomous Region are excellent,and the mining of mineral resources and tourism are the mainstay of economic development in the region,but many tailings wastes will be generated when mining mineral resources,and the main treatment method for tailings wastes is storage,so the study of tailings reservoirs and surrounding environment is very important.In view of this,In this paper,the tailings of typical copper-lead-zinc tailings ponds around Lhasa and the surrounding soil of the tailings ponds are selected as the research objects,and the tailings of 5 tailings ponds are collected for heavy metal content analysis and heavy metal leaching experiments,and the tailings with the highest copper,lead and zinc content are selected.Carry out environmental ecological risk assessment for the soil around the reservoir.This paper provides data support for the management of tailings ponds and the establishment and governance of heavy metal contaminated soil early warning systems.The results show that:1.The selected 5 tailings are numbered respectively: 1T,2T,3T,4T,5T tailings.The contents of Cu,Pb,Zn and TFe in the five tailings are relatively high.In this paper,the tailings pond tailings（1T）with the highest Cu,Pb and Zn contents are selected as the key research object.The contents of Cu,Pb and Zn in the tailings They were 1800 mg/kg,4480 mg/kg,and 3350 mg/kg,respectively;the contents of Cu and Mn in the soil around the tailings pond were relatively high,and the spatial variation was not obvious;with the increase of soil depth,the concentrations of Cu,Pb,and Zn increased.The content gradually decreased between 24.2mg/kg-93.8mg/kg,13.94mg/kg-308mg/kg,21.27mg/kg-236.95mg/kg,and the Cr content gradually increased with the increase of soil depth and was between Between36.6mg/kg-127mg/kg,the content of Mn element gradually increased with the increase of soil depth,between 148.98mg/kg-378.98mg/kg.2.Through the leaching simulation experiment,it was found that when the 1T,2T,3T,and 4T tailings were leached with a p H=6.0 leaching solution,the concentrations of four heavy metal elements such as Cu,Pb,Zn,and Mn were higher in the leaching solution.As the p H of the leaching solution increases,the concentration of heavy metals in the leaching solution gradually decreases;for the heavy metal Cr,the peak value appears when the leaching solution with p H=6.0 and p H=9.0 is leached,and the leaching rate is larger,which is 12.22%,respectively.-15.926% and 17.78%-20%.The leaching rate of Cu is relatively low,especially in 5T tailings.The maximum leaching rate does not exceed0.02%,and the minimum is only 0.009%.The leaching rate of Cu,Pb and Zn is generally low,but the concentration of the three heavy metals in the leaching solution is obviously different.The concentration of Cu,Pb and Zn in the leaching solution of 4T tailings has the most obvious difference,and its leaching rate is the largest.3.The heavy metal pollution and heavy metal ecological risk assessment of the soil around the 1T tailings pond found that the heavy metal pollution in the surface soil was the most serious,and the pollution in the middle and lower soils was relatively light.The severity of heavy metal pollution is: Pb>Cu>Zn>Cr>Mn.According to the results of the potential ecological hazard index,the order of the potential ecological hazard risk of heavy metals in the soil around the 1T tailings pond is:Pb>Cu>Cr>Zn.The heavy metal ecological risk index of the soil samples around the tailings pond shows that: all 10 sample points have potential ecological risks of heavy metals,which are between slight potential ecological risks and moderate potential ecological risks;The No.6 sample site has the highest potential ecological hazards,and its risk indices are: 169.12 and 216.79,respectively,and its potential ecological risks are all moderate potential ecological risks.