者海铅锌渣中重金属的赋存形态及环境风险评价

Speciation and Risk Assessment for Heavy Metals in Lead and Zinc slag at Zhehai,China

以者海铅锌中和渣和水淬渣为研究对象,利用原子吸收和原子荧光分光光度法测定其重金属（As、Pb、Cu、Zn、Cd、Cr）的含量,采用BCR连续提取法研究了重金属元素的形态分布特征,利用单因子污染指数法、潜在生态风险评价指数法和风险评价编码法对该铅锌渣中重金属的超标水平及生态风险进行评价。结果表明：（1）参考土壤环境质量三级标准,中和渣中的Cd、Zn、Cu超标倍数分别为215、20.6和4.65,水淬渣中的Cd、Zn、As超标倍数分别为11.51、8.62和3.075,中和渣中Cd、Zn、Cu和水淬渣中Cd、Zn污染程度较严重,水淬渣中的As也存在轻度污染性,对生态环境存在威胁。（2）中和渣中Pb、Zn及Cr的主要形态为可还原态,Cd和Cu的主要赋存形态为弱酸提取态,As的残渣态所占比例最大;水淬渣中的Pb、Cd、Cr、As主要赋存于残渣态,Cu和Zn的主要形态分别为可氧化态和可还原态。（3）潜在生态风险评价结果表明,中和渣中Cd和Zn分别处于很高和高生态风险等级,水淬渣中Cd处于偏高生态风险,其他几种重金属则表现为低生态风险。铅锌渣RI值介于183.81~5357.58,为中等-严重生态风险,Cd的风险贡献率最高。（4）风险评价编码法研究表明,中和渣中Cd和Cu分别处于极高和高风险级、Cr和As处于中等风险级;水淬渣中Cd、Zn、As均处于中等风险级,其他重金属处于低风险级,并且中和渣和水淬渣的RAC值顺序为Cd〉Cu〉Cr〉As〉Zn〉Pb和Zn〉As〉Cd〉Cr〉Cu〉Pb。

Heavy metals including As,Pb,Cu,Zn,Cd and Cr in Lead and Zinc slag from Zhehai Area,China were determined and their ecological risk was discussed in this paper. The chemical fraction of the heavy metals were investigated with BCR sequential extraction procedure,and ecological risk of heavy metals was assessed based on the single factor pollution index,the potential ecological risk index and the risk assessment coding method. Results show that,（ 1） according to grade Ⅲ of China environmental quality standard for soil（ GB15618-1995）,contents of heavy metals（ Cd,Zn and Cu in neutral dregs,Cd,Zn and As in water-quenched slag） are higher than the limit of the standard. Cd,Zn and Cu in neutral dregs and Cd,Zn in water-quenched slag have high pollution levels,and As in water-quenched slag has a little pollution level;（ 2） according to neutral dregs,Pb,Zn,and Cr are mainly in the reducible fractions,Cd and Cu are mainly in the acid soluble fraction,and As exists mainly in residual fractions. And for water-quenched slag,residual fraction is the dominant form of Pb,Cd,Cr and As. Cu and Zn are mainly in oxidizable and reducible fractions;（ 3） based on calculation of potential ecological risk index and risk assessment,Cd and Zn in neutral dregs show considerable and high ecological risk,while Cd in water-quenched slag has a little higher ecological risk comparing with other heavy metals. The potential ecological risk values are in the range of 183. 81-5357. 58,and they are at the medium to high ecological risk levels. Cd is the main ecological risk contributor; and（ 4） RAC assessment results show that Cd and Cu are of very high and high risk while Cr and As are of medium risk in neutral dregs. Cd,Zn and As in water-quenched slag represent medium risk comparing with other heavy metals of low risk. The order of RAC index of different heavy metals in neutral dregs is Cd〉Cu〉Cr〉As〉Zn〉Pb and in water-quenched slag is Zn〉As〉Cd〉Cr〉Cu〉Pb.