Study On The Technical Specification Formulation Of Heavy Metal Risk Assessment Of Pb-Zn Tailing Pond

Heavy metals in lead-zinc tailing pond can enter the environment through many ways,this cause serious heavy metal pollution to the surrounding water,soil and crops,and even threatens the health of the residents.Therefore,it is necessary to evaluate the heavy metal pollution risk of lead-zinc tailing pond to surrounding environment and to formulate technical specification of heavy metal risk evaluation,to divide the degree of heavy metal risk for Pb-Zn tailing pond.The lead-zinc tailing pond in Guangdong Province and its surrounding environment as the research object,the surface soil in tailing pond and the surface water,groundwater,farmland soil and crops aound tailing pond were collected,heavy metal elements(Pb,Zn,Cu,Cr,Cd,Ni and As)were determined,based on investigating the heavy metal contents of samples surrounding environment,the degree of heavy metal pollution around the lead-zinc tailing pond and its environmental risk were evaluated,technical specification of heavy metal risk assessment for lead-zinc tailing pond was established and the risk of heavy metal pollution in the tailing pond was evaluated with this method.The results of research are:Only the contents of Zn,Ni and As in the surface water which collected in downstream of the Pb-Zn tailing pond exceeded the standard value,the results of nemero pollution index showed that surface water is in the degree of warning value.Heavy metal contents in groundwater around tailing pond was below the standard value,the result of evaluation showed that the groundwater was in the degree of non-pollution.The contents of heavy metal in paddy soil were higher than that in vegetable soil,compared with II level criterion of environmental quality standard for soils,the total exceeded rate of heavy metal decreased in the order of Cd>Pb>Zn>As>Ni>Cu,the content of Cr was below the II level criterion;Three evaluation methods were used to evaluate the farmland soil around the tailing pond,the results of nemero index method and fuzzy comprehensive evaluation method were severe pollution,and the potential ecological hazard index method was moderate pollution.The content of Pb,Cr,Cr,Cd,Ni and As in rice and leafy vegetables exceeded the limited value,the results of evaluation showed that rice and leafy vegetables belongs to the degree of heavy pollution;In non-leafy vegetables,only the content of Cr and Cd exceeded the standard value,the results of evaluation showed that non-leafy vegetables belong to the degree of slight pollution.Health risk assessment showed that the non-carcinogenic and carcinogenic risk of adults and children in the study area are unacceptable.Based on investigation and evaluation of heavy metal contamination around the tailing pond,a technical specification for the risk assessment of heavy metal contamination in lead-zinc tailing pond to surrounding environment was established,the risk was evaluated through two major indexes including the atmospheric environment and leakage water,atmospheric environment index including total toxicity of heavy metals in atmospheric and atmospheric environmental protection distance,the index of leakage water including the toxicity of heavy metals in observed leakage water and total toxicity of heavy metals in leaching water from simulated acid rain by leaching tailings.Each index was calculated separately and the risk of these two indexes was determined according to a certain risk level,finally,the risk level of heavy metal pollution of lead-zinc tailing pond to surrounding environment was determined according to the risk level classification.The risk of the lead-zinc tailing pond was evaluated with the technical specification,the result of evaluation showed that the risk level of heavy metal contamination of the tailings pond was at a larger and more than larger level when the measured water leakage data was used;the result of evaluation when the leaching liquid data was used is similar to the result of evaluation when the measured water leakage data was used,the result of evaluation showed that the risk level of heavy metal contamination of the tailings pond was at a larger and more than larger level when the leaching liquid data was used,the risk of heavy metal pollution is in the degree of larger risk when the leakage ratio is 1%,the risk of heavy metal pollution of two evaluated methods is in the degree of heavy risk when the leakage ratio is 10%?20%?50%.