铜陵某富铜尾矿库下游重金属污染特征与生态风险

Pollution Characteristics and Ecological Risk of Heavy Metals in the Downstream of a Copper-Rich Tailings Pond in Tongling

金属矿山尾矿库是潜在的环境污染源,若处置不当,将污染周边环境并威胁人类健康。本研究以铜陵某富铜型尾矿库及其周边水土中5种重金属(Cu、Zn、Pb、Cd和Cr)为研究对象,采用BCR逐级提取、浸出试验及两种风险评估模型,揭示了5种重金属的污染特征及生态风险。结果表明,尾矿库中Cu、Zn和Cd的含量分别是铜陵土壤背景值的13.18、7.03、13.48倍;尾矿库下游土壤中Cu、Cd和Pb的平均含量超过铜陵土壤背景值;河流底泥中Zn、Cu、Cd和Pb的平均含量均高于长江下游沉积物背景值。BCR结果表明,尾矿库及下游水土中Cr以残渣态(F4)为主,Cd的可交换态(F1)占比最高。浸出实验结果表明,尾矿中5种重金属在强酸和强碱下浸出率较高。单因子指数(Pi)结果表明尾矿中Cu(13.18)、Zn(7.03)和Cd(13.4)处于重污染水平;库下游土壤和底泥中Cd、Cu和Pb为重度污染,距尾矿库最远处的河水中Cu、Zn和Cd为轻污染。风险评估编码(RAC)结果表明研究区域中Cd的潜在生态风险最高。

Metal mine tailings ponds are potential sources of environmental pollution;if improperly disposed of,they will pollute the surrounding environment and pose a serious threat to human health.This study takes five heavy metals(Cu,Zn,Pb,Cd and Cr)in the copper-rich tailings pond in Tongling and its surrounding water and soil as the research objects,and uses BCR step-by-step extraction,leaching tests and two risk assessment models to systematically reveal the pollution characteristics and ecological risks of the five heavy metals.The results showed that the contents of Cd,Cu and Zn in the tailing pond were 13.48,13.18 and 7.03 times higher than the background values of Tongling soil,respectively.The average contents of Cu,Cd and Pb in the soil downstream of the pond exceeded the background values of Tongling soil.The average contents of Cu,Zn,Cd and Pb in river sediments were higher than the background values of sediments in the lower reaches Yangtze River,respectively.The BCR extraction results showed that Cr in the tailings pond and downstream soil and river was mainly in the residue state(F4).The acid soluble/exchangeable state(F1)of Cd accounted for the highest percentage.In addition,the leaching results of heavy metals showed that the five heavy metals in the tailings were leached at higher rates under strong acid and alkaline conditions.The results calculated by single factor index(Pi)showed that Cu(13.18),Zn(7.03)and Cd(13.4)were at heavy contamination levels.Also,Cd,Cu and Pb in the soil and sediment downstream of the pond were heavily contaminated.Copper,Zn and Cd in the river water far from the tailings pond were at light contamination levels.The results from risk assessment code(RAC)indicated that Cd in the tailings pond and surrounding soils and sediments ex had the highest potential ecological risk.