多金属矿区土壤重金属垂向污染特征及风险评估

Vertical Pollution Characteristic and Ecological Risk Assessment of Heavy Metal of Soil Profiles in Polymetallic Ore Mine

重金属在土壤中向下迁移可能会对地下水造成污染,了解重金属在剖面上的迁移特征对污染控制与防范有重要意义.为深入了解多金属矿区尾矿库土壤重金属垂直迁移与生态风险问题,分层采集了某多金属矿区尾矿库坝下附近0-100 cm 深度的土壤样品,分析检测了不同深度土壤中Cr、Cd、Pb、Cu、Zn、Ni 总量及有效态含量.综合考虑多元素协同作用、毒性水平、污染浓度以及环境对重金属污染敏感性等因素,采用Hakanson 潜在生态风险指数法对土壤污染状况及生态环境风险进行了评价,并对土壤中铅、锌重金属的形态垂向分布特征及其迁移能力进行了分析研究.结果表明,研究区域土壤重金属污染严重,垂向污染也达到了一定的深度,上层土壤、中层土壤综合污染指数均达到重度污染级别,下层土壤综合污染指数达到中度污染级别.供试土壤的污染程度最重的指标为Pb 和Zn,污染最重的土层为0-30 cm 上层土壤.从生态风险来看,单项潜在生态风险指数在3.07-77.1 之间,上层土壤单项潜在生态风险Cd〉Cu〉Pb〉Ni〉As〉Zn,矿区场地土壤修复过程中应重点关注Cd、Cu 的生态风险影响;此外,由于As 在土壤中具有较强的垂向迁移能力,也应予以重点关注.

Heavy metal pollution in soil may cause groundwater pollution for its migration and it is important to understand the migration characteristics of heavy metals in soil profile. To better understand the heavy metals pollution problems of soil in polymetallic ore Mine area, we collected soil profile about 0~100 cm depth near mine tailings. The concentration of Cr, Cd, Pb, Cu, Zn, Ni in soil was detected. The Hakanson potential ecological risk index method was used to evaluate the soil pollution and ecological environment risk both consider the multi-elements synergistic, the toxicity level, the pollution concentration and the sensitivity of the heavy metal pollution. The zinc and lead heavy metal form distribution characteristic and migration ability was also analysis. The result showed that the soil is serious polluted by heavy metal in study area. Pollution has reached a certain depth, 0~30 cm upper layer soil and 30~60 cm middle layer soil pollution index reached severe pollution levels, 60~100 cm bottom layer soil pollution index reached moderate pollution levels. Characteristics of pollutants in study area are Pb and Zn, the most heavily contaminated soil is top layer soil. But the individual potential ecological risk in the study area is range between the ecological risks 3.07~77.1, the range of individual potential ecological risk in upper layer soil is Cd > Cu > Pb > Ni > As > Zn. So the ecological risk of Cd and Cu should be a key point during soil remediation in this area, as well as As element which has strong vertical migration ability in the soil.