黔西北炼锌矿区土壤重金属形态分析及风险评价

摘要

Contents and spatial distribution of heavy metals in the soils of the zinc mining area in northwestern GuizhouProvince were investigated and characterized and pollution degrees and risks of the heavy metals were analyzed and assessed with the Tessier sequential extraction method and risk assessment code (RAC),respectively.Results show that the average contents of all the studied heavy metals,except Cr and Ni,were higher than their respective background values of Guizhou Province.The soils were seriously contaminated with Pb,Zn and Cd in samples.Fractionation of the pollutants shows that in the soils and slag,Pb,Zn and Mn existed mainly in the form of residue (accounting for 45.91％,55.11％ and 42.71％ of their respective total),and in ferromanganese bound form (33.33％,28.26％ and 41.78％),Cd in exchangeable form and carbonate bound form,together making up 30.63％;Cu in organo-bound form (65.11％) and then in the form of residue (30.79％);and Cr and As in the form of residue (both exceeding 90％).RAC shows that Cd in the soil poses a very high potential ecological risk,while the others have relatively low ones.%为研究黔西北炼锌矿区土壤和矿渣中重金属总量及形态分布特征,采用Tessier五步连续提取法和风险评价编码法(RAC)探讨其污染程度.结果表明,除Cr和Ni外,其他各重金属平均值均超出贵州省的土壤背景值,其中Pb、Zn、Cd污染严重.形态分析表明,土壤和矿渣样品中Pb、Zn、Mn以残渣态(分别占其总量的45.91％、55.11％、42.71％)和铁锰结合态(分别占其总量的33.33％、28.26％、41.78％)为主;Cd的可交换态和碳酸盐结合态之和占总量的30.63％;Cu的有机结合态为65.11％,其次是残渣态30.79％;Cr和As则以残渣态为主要形态,平均占比均超过90％.RAC评价结果表明,矿区周边土壤中Cd元素具有极高的潜在生态风险,其他重金属潜在生态风险水平较低.