某矿区砷碱渣堆场周边土壤重金属污染评价及潜在生态风险分析

为了解湘中某矿区砷碱渣堆场周边土壤的重金属污染特征,对堆场周边土壤中Hg、As、Pb、Zn、Cd、Cu、Cr 7种重金属含量进行采样,分析其污染特征和来源,并对潜在生态风险进行评价。结果表明:堆场周边土壤中Hg、As、Pb、Zn、Cd、Cu、Cr平均质量分数分别为2.61、209、41.3、209、3.49、4.34、45.7 mg·kg~(-1),其中Hg、As、Pb、Zn、Cd平均含量分别是背景值的22.5、13.3、1.39、2.21、27.7倍。地累积指数评价结果显示,Hg、As、Cd单项Igeo达到严重累积污染级别的比例分别为25%、6.25%、18.8%。多种重金属潜在生态风险评价表明,区域内所有点位的潜在生态风险指数均在"强"及以上风险等级,其中62.5%的点位为"很强"等级,区域总体处于"很强"风险等级。多元统计表明,Hg、As、Pb、Cu、Zn、Cd主要来源于矿山开采、冶炼和交通运输,Cr来源于成土母质。

Pollutions and potential ecological risk of heavy metals in soils around waste arsenic-containing alkaline sites

It is important to control the spatial distribution and pollution of heavy metals in soil environment, Although the potential ecological risk index method has already been widely applied on the assessment of heavy metals pollution in different types of industrial areas, there are few concerned about heavy metal contents in the surrounding soils of mixed smelting slag(arsenic residue and slag). In this study, arsenic residue in the middle of Hunan Province was sampled and the contents of Hg, As, Pb, Zn, Cd, Cu and Cr of the soil and the soil characteristics were analyzed. The results showed that the average mass fraction of Hg, As, Pb, Zn, Cd, Cu and Cr in the soil were 2.61, 209, 41.3, 209, 3.49, 4.34, 45.7 mg·kg^-1. The average contents of Hg, As, Pb, Zn and Cd were 22.5, 13.3, 1.39, 2.21 and 27.7 times than the background value, respectively. The pollution extent of heavy metals in soils by geo-accumulation index(I_geo) showed that the proportion of serious accumulation of pollution of single I_geo of Hg, As, Cd was 25%, 6.25%, 18.8% respectively. This assessment shows that the average potential ecological risk index of all the samples is above the conderable ecological risk level, of which 62.5% is very high ecological risk, and the area is in very high ecological risk graded. The results also showed that Hg, As, Pb, Cu, Zn and Cd are mainly derived from mining, smelting and transportation. While Cr is derived from soil parent material.