某典型废弃硫酸场地土壤重金属污染特征与评价

Heavy metal pollution characteristics and assessment in soil of a typical abandoned sulfuric acid site

硫酸生产场地可能存在严重的土壤重金属污染,调查并分析硫酸场地土壤重金属污染及迁移规律是其安全利用的基础.本研究以某废弃硫酸场地为例,采集0—3 m深度范围的土壤样品,测定其中的Pb、Cd、Cu、Ni、As、Hg含量,分析重金属的空间分布特征、来源及迁移行为,并对其进行内梅罗综合污染指数和潜在生态风险指数评价.结果表明,Cd、Cu、Ni、Hg的含量均在GB36600—2018中的第二类用地筛选值以下,而Pb、As的超标率分别是8.33%、43.3%.表层重金属主要分布于原料和废渣的堆积区.除Ni外,重金属整体呈表面聚集,同时表现出明显的垂向迁移.Pb仅在硫酸原料区和过磷酸钙原料区超标;As在所有功能区均超标,在土壤层最底部3 m处依然有超标点位,其中最大值出现在硫酸原料区,超标倍数达20.3倍.不同功能区土壤的污染程度和潜在生态风险依次为:过磷酸钙原料区>硫酸原料区>硫酸废渣区>硫酸生产区>成品库区>过磷酸钙生产区>餐厅及仓库区.各功能区均属于重度污染,除过磷酸钙生产区和餐厅及仓库区属于强生态风险外,其它功能区均处于极强生态风险.场地土壤中Pb、Cd主要来自过磷酸钙原料,Cu、As主要受硫酸原料堆积的影响,Hg主要来源于硫酸生产,Ni则同时受到生产活动和地质背景的影响.

There may be serious pollution of soil with heavy metals in the sulfuric acid production sites,therefore the safe utilization of such sites should be based on the investigation and analysis of soil heavy metals pollution and migration law.This study takes an abandoned sulfuric acid site as an example,the contents of Pb,Cd,Cu,Ni,As and Hg were determined in soil with depth of 0—3 m.The spatial distribution characteristics,the sources and migration behaviors of heavy metals were analyzed.The heavy metals pollution was assessed by the Nemerow comprehensive pollution index and potential ecological risk index.The results showed that the contents of Cd,Cu,Ni and Hg were lower than the filter values of the second type of land in GB36600—2018,while the over-standard rates of Pb and As were 8.33%and 43.3%,respectively.The surface heavy metals were mainly distributed in the accumulation areas of raw materials and waste residues.The heavy metals were aggregated on the surface as a whole except for Ni and showed obvious vertical migration.Pb exceeded the standard only in sulfuric acid and superphosphate raw material area,while As exceeded the standard in all functional areas.There were still sampling points exceeding the standards at the bottom of the soil layer(the depths of 3 m),and the maximum exceeding multiple was 20.3 times in the sulfuric acid raw material area.The pollution levels and potential ecological risks of soil in different functional areas were as follows:superphosphate raw material area>sulfuric acid raw material area>sulfuric acid waste residue area>sulfuric acid production area>finished products warehouse area>superphosphate production area>restaurant and warehouse area.All the functional areas are at the serious pollution level.Except for the superphosphate production area and the restaurant and warehouse area belong to the strong ecological risk,other functional areas are in the extremely strong ecological risk.Pb and Cd in the site soil are mainly derived from the superphosphate materials,Cu and As are mainly affected by the sulfuric acid materials,Hg mainly comes from the production of sulfuric acid,and Ni is both controlled by production activities and geological background.