湘西某电解锰废弃场地土壤中重金属垂直分布特征及其修复效果评价

Repair Effect Evaluation and Vertical Distribution Characteristics of Heavy Metals in the Soil of Electrolytic Manganese Waste Site in Xiangxi

以湘西某电解锰企业高浓度Mn、Pb、Zn、Cr复合污染场地为研究对象,对修复前场地土壤、工程清挖后基坑底部与坑壁土壤、稳定化修复后土壤及场地周边地表水中pH、Mn、Pb、Zn、Cr进行了检测,采用美国环境保护署(USEPA)的人体暴露风险评价模型对稳定化修复后土壤与周边地表水中重金属进行了健康风险评价.结果表明,场地修复前土壤中Mn、Pb、Zn、Cr总量分别超过《重金属污染场地土壤修复标准》(DB43/T1165-2016)中居住用地标准限值2.2、2.0、9.9、3.4倍。修复前场地土壤重金属Mn、Pb、Zn、Cr垂直分布特征各异,Mn随着土壤深度增加呈下降趋势,Pb则随着土壤深度增加呈上升趋势,Zn的垂直分布特征不明显,而Cr的垂直分布较均匀。稳定化修复后土壤中Mn、Pb、Zn与Cr总量与中性浸出液含量均未超标,河道清淤后地表水中重金属含量显著降低,且均未超过地表水环境质量标准(GB3838-2002)Ⅲ类标准限值。健康风险评价结果显示,场地修复后土壤与地表水的健康风险均在可接受范围内,土壤和地表水的总健康风险主要来源于非致癌物质Pb。

A high concentration of Mn, Pb, Zn and Cr combined pollution site in an electrolytic manganese enterprise in Xiangxi was taken as the research object. To repair after digging foundation pit at the bottom of the previous one site soil, engineering, soil stabilization and the pit wall after repair and area surface water in the soil pH, Mn, Pb, zinc and Cr were tested, The human exposure risk assessment model of the US environmental protection agency (US EPA) was used to evaluate the health risk of heavy metals in soil and surrounding surface water after stabilization restoration. The results showed that the total amount of Mn, Pb, Zn and Cr in the soil before the site restoration exceeded the limit values of 2.2, 2.0, 9.9 and 3.4 times in the standards of soil remediation standards for heavy metal contaminated sites (DB43/T 1165-2016), respectively. Before restoration, the vertical distribution characteristics of heavy metals Mn, Pb, Zn and Cr in the soil of the site are different. Mn tends to decline with the increase of soil depth, while Pb tends to rise with the increase of soil depth. The vertical distribution characteristics of Zn are not obvious, while the vertical distribution of Cr is relatively uniform. Stabilization in the soil after the restoration of Mn, Pb, zinc and total Cr and neutral leaching liquid content are not overweight, heavy metals in surface water content decreased significantly after river dredging, and were not more than surface water environment quality standard (GB3838-2002)Ⅲ class standard limit. The results of health risk assessment showed that the health risks of soil and surface water after site remediation were all within the acceptable range, and the total health risks of soil and surface water were mainly from non-carcinogenic Pb.