潼关矿区土壤重金属污染潜在生态风险评价

Potential ecological risk assessment of soil heavy metal pollution in Tongguan mining area

为探明潼关矿区周边重金属污染状况,采集了潼关县三河口废弃尾矿场、沙坡废弃尾矿场、麻峪河废弃尾矿场、乌家河废弃尾矿场4个治理区的农田土壤、土场土样和矿渣样品75份,测定了土样中重金属(Hg、Pb、Cd、Cr、As、Cu、Zn)含量,采用单因子指数法、潜在生态风险指数法对研究区重金属污染状况进行潜在生态风险评估。结果表明:潼关矿区的Hg、Pb、Cd、Cr、As、Cu、Zn潜在生态危害系数平均值分别为41.4、0.58、60.8、0.44、4.33、4.51、0.36,废弃矿区周边农田的Cd污染最为严重,为中度污染,其次是Hg,为轻污染;Cu污染达到了警戒值。矿区矿渣的Cd污染和Hg污染程度为重度污染,污染等级为Ⅴ级,其中Cd污染的潜在生态危害风险等级很高,Hg为较高;Cu的污染等级为Ⅳ级,污染程度为中等污染,Zn污染等级为Ⅲ级,污染程度为轻污染,这些重金属含量较高的尾矿渣、氰化渣随意堆放是当地基本农田的污染源,所以处理这些尾矿渣是解决环境和土壤问题的当务之急。用于当地重金属污染修复的取土场中,仅有沙坡废弃尾矿场周边的3个土场不存在重金属污染,可作为重金属污染修复的清洁土源。4个矿区的综合生态危害指数由大到下依次为麻峪河废弃尾矿场、乌家河废弃尾矿场、三河口废弃尾矿场、沙坡废弃尾矿场,危害指数分别为400、337、264、225,潼关矿区整体的综合生态危害指数为241,潜在风险等级为中等。

In order to ascertain the pollution status of heavy metals around Tongguan mining area,75 samples of farmland soil,soil samples and slag samples from four treatment areas of Sanhekou abandoned tailings yard,Shapo abandoned tailings yard,Mayuhe abandoned tailings yard and Wujiahe abandoned tailings yard were collected,and the contents of heavy metals(Hg,Pb,Cd,Cr,As,Cu,Zn)in soil samples were determined.Potential ecological risk assessment of heavy metal pollution in the study area was carried out by single factor index method and potential ecological risk index method.The results showed that:The average values of potential ecological hazard coefficients of Hg,Pb,Cd,Cr,As,Cu and Zn in Tongguan mining area were 41.4,0.58,60.8,0.44,4.33,4.51 and 0.36,respectively.The Cd pollution of farmland around the abandoned mining area was the most serious,which reached moderate pollution.The second serious pollution was caused by Hg and was light pollution.Cu pollution reached the warning value as well.The degree of Cd and Hg pollution of slag in mining area was serious pollution,and the pollution grade was grade V.Among them,the potential ecological risk level of Cd pollution was very high and Hg was high;the pollution level of Cu was grade IV,the pollution level was moderate pollution,and the pollution level of Zn was grade III,the pollution level was light.The tailings with high heavy metal content and cyanide slag at random were the pollution sources of the basic farmland.Therefore,it is urgent to deal with these tailings to solve the environmental and soil problems.Only the soil around the abandoned tailings yard in Shapo did not contain heavy metal pollution and could be used as a clean soil source for remediation of heavy metal pollution.The comprehensive ecological hazard index of the four mining areas from large to low was:Mayuhe abandoned tailings field,Wujiahe abandoned tailings field,Sanhekou abandoned tailings field and Shapo abandoned tailings field.The ecological hazard index was 400,337,264 and 225 respectively.The overall comprehensive ecological hazard index of Tongguan mining area was 241,and the potential risk grade was medium.