某多金属矿周围牧区土壤重金属形态及环境风险评测

采集某多金属矿周围牧区土壤样品,分析土壤中含量相对较高的Cr、Cu、Ni、Pb、Sr、Zn的赋存形态,采用污染负荷指数法(PLI)、内梅罗综合指数法、风险评价编码法(RAC)和聚类分析比较探讨该矿区周围土壤重金属污染程度。结果表明,该区域土壤中大部分重金属含量都超过了对照土壤背景值。PLI与内梅罗综合指数法分析显示,该矿区周围土壤处于被污染状态,重金属元素污染程度顺序为ZnCuNiCrSrPb。赋存形态分析表明,重金属的主要形态是残渣态,其中Sr的可交换态(4.99%~42.11%)和碳酸盐结合态(4.05%~41.10%)所占百分比最高,Cu和Ni的有机结合态明显高于其他元素。RAC结果显示Sr处于高风险,Cu、Ni、Pb和Zn基本处于中低风险,Cr基本处于无风险等级。重金属非残渣态聚类分析结果表明,该区域土壤中重金属非残渣态可分为两个集群,分别是Ni、Pb、Cu、Cr以及Zn、Sr,其中Sr和Zn环境污染风险最大。以上结果表明该地区已受到一定程度的污染,并且存在继续污染的风险,应该加强该地区金属矿开采和尾矿的管理和监督。

Speciation distribution characteristics of heavy metals in soil of multi-metal mining pastoral area and pollution assessment

Mining and tailings may bring impacts on surrounding environment, one of which is heavy metal pollution. The analysis of heavy metal speciation and distribution can provide scientific basis for control, management and remediation of soil pollutants. The total and extractable contents of heavy metals(Cr, Cu, Ni, Pb, Sr, Zn) in soil samples collected around a multi-metal mining area were measured and the degree of heavy metal pollution was evaluated with pollution load index(PLI), Nemerow index method and risk assessment code(RAC) in this research. The results showed that the total contents of most measured heavy metals were higher than the background values of soil. The PLI results indicated that the soil around the mining area was in the middle pollution level and the degree order of heavy metal pollution was Zn > Cu > Ni > Cr > Pb > Sr. Furthermore, the occurrence state of measured heavy metals showed that the main chemical speciation was residual fraction in these soil samples. The exchangeable fraction(4.99%~42.11%) and carbonate fraction(4.05%~41.10%) of Sr were the highest, while the organic fractions for Cu and Ni were obviously higher than that of other elements. The RAC results indicated that Sr was in high ecological risk; Cu, Ni, Pb and Zn were in a substantially low risk, while Cr showed no risk. Cluster analysis(CA) showed that the non-residual fractions for measured heavy metals in soil samples could be revealed as two clusters:Ni, Pb, Cu and Cr, Sr and Zn. Sr and Zn in the measured heavy metals were the most risk elements to environmental pollution. The above results suggested that this region has been contaminated to varied extents, and there exists further pollution risk. So, the management and supervision of multi-metal mining and tailing in this region should be strengthened.