某炼铁厂遗留场地重金属污染空间分布特征及风险评价

Spatial Distribution Characteristics and Risk Assessment of Heavy Metal Pollution in a Legacy Site of an Iron-making Plant

以某炼铁厂遗留污染场地作为研究区域,共采集土壤样品598个、地下水样品7个,在详细调查研究区土壤和地下水重金属污染状况的基础上,运用多元统计分析结合GIS插值方法研究了该炼铁厂遗留场地土壤和地下水中重金属污染的空间分布特征,并通过污染负荷指数法和潜在生态指数法对研究区土壤重金属污染状况和潜在生态风险进行了风险评估。结果表明:研究区土壤中重金属浓度超标率依次为Cd<As<Hg<Pb<Ni;土壤重金属污染以局部点状污染为主;受地层岩性变化的影响,土壤重金属污染羽范围随着地层深度的增加呈减小的趋势;地下水中重金属仅As浓度存在局部小范围超标现象,超标率为28.57%,主要原因可能是由于土壤中重金属在下渗过程中发生了一定的氧化还原反应,生成的产物溶解度较低,不易溶解于地下水中,加之局部地下水循环较快不利于地下水中各组分的进一步富集;研究区土壤重金属污染负荷指数P_(zone)=1.05,属轻微污染,土壤重金属潜在生态风险指数RI_(平均值)=714.16,存在极高的潜在生态风险,该炼铁厂3、4号高炉区域生产过程中遗留的重金属废渣是造成该场地土壤重金属污染和极高的潜在生态风险的主要原因。

Using the contaminated site left by an iron-smelting plant site as the research area,based on a detailed investigation of the heavy metal pollution in the soil and groundwater in the study area with a total of 598 soil samples and 7 groundwater samples,this paper studies the spatial distribution cha-racteristics of heavy metal pollution soil and groundwater in the legacy site in the ironworks using multivariate statistical analysis combined with GIS interpolation methods to investigate the soil heavy metal pollution status and assesses the potential ecological risks using the pollution load index method and potential ecological index method.The results show that the exceeding rates of heavy metals in soil follow the increasing order of Cd<As<Hg<Pb<Ni.Soil heavy metal pollution is mainly local spot pollution.With the change of stratum lithology,the range of soil heavy metal pollution plume decreases with the increase of depth.Only the concentration of arsenic in groundwater exceeds the standard in a small range,with an exceeding rate of 28.57%,and the main reason is probably that the oxidation-reduction reaction of heavy metals in the soil occurs during the infiltration process,whose product has low solutility and is not easy to dissolve in groundwater and the local groundwater circulation is faster,which is not conducive to the further enrichment of groundwater components.The pollution index of the study area is P_(zone)=1.05,which is a slight pollution.The average potential risk index(RI)is 714.16.The study area has extremely high potential ecological risks.The heavy metal containing waste residue left over from the production process in the No 3,4 blast furnace areas of the ironworks is the main cause of soil pollution and ecological risks of the site.