场地土壤重金属污染健康风险评价及固化处置-以东莞市某电镀厂搬迁场地为例

The Health Risk Assessment and Curing Treatment of Site Soils Contaminated by Heavy Metals: Application in One Electroplating Factory Relocation Field in Dongguan City, China

以广东省东莞市某典型电镀厂搬迁场地为研究对象,在对搬迁场地土壤进行全面调查及土壤重金属污染风险评价的基础上,研发了基于粘土矿物的重金属深度固化技术,以重金属污染土壤为原料制备烧结砖体,实现重金属污染土壤的资源化利用。土壤重金属含量分析结果表明46个土壤样品中镉、汞、镍及锌含量均低于中国《土壤环境质量标准》(GB 15618─1995)中二级标准值,但砷、铜、铬和铅含量在部分样点高于国家二级标准值。健康风险评价结果显示该场地中铬、铅、砷和铜对儿童存在潜在的非致癌危害,而砷对成人、儿童均存在明显的致癌风险。在以上该场地土壤重金属含量调查和重金属健康风险评价基础上,对重金属超标土壤采用基于矿物晶体结构的异位固化处置,以粘土为基质,使污染土壤与粘土充分混合后压制成砖,煅烧后重金属以晶体结构的形式固定于砖体中。采用美国环保署EPA基于毒性对废物进行危险或非危险性鉴别的标准方法 TCLP(US EPA 1311)的毒性浸出实验结果表明,浸出液中重金属浓度低于《地表水环境质量标准》(GB 3838─2002)三类水标准值,实现场地重金属污染土壤的无害化处置。该研究针对典型搬迁工业场地建立了一套行之有效的重金属污染土壤风险评价及无害化处置的工艺流程,可为促进广东省土壤污染修复产业的形成与发展提供借鉴。

Soils contaminated by heavy metals, due to their non-biodegradability and persistence, have received great attentions. In this study, 46 soil samples were collected from the typical electroplating relocated site in Dongguan, Guangdong Province, China. Soil physicochemical properties including heavy metal contents (Cd, Cu, Ni, Zn, Cr, Pb, As and Hg) were analyzed. The analysis results showed that the contents of Cd, Hg, Ni and Zn in this study site were below the standard values of level two of the Chinese soil environmental quality standard (GB 15618─1995), whereas the contents of Cr, Pb, As and Cu in some samples were above the standard values. The health risk assessment results indicated that Cr, Pb, As and Cu in this study site had non-carcinogenic risk potential on children, and As had obvious carcinogenic risk both on adults and on children.Kaolin was used as the stabilization agent for treatment of the contaminated soils at designed weight ratios before being sintered at 1 100 ℃. The results of leaching experiments with the toxicity characteristic leaching procedure (TCLP) indicated that the contaminated heavy metals in soils were structurally stabilized in the sintered solids and there was a much lower risk of secondary pollution of the stabilized heavy metals when exposed to the natural environment. The technology obtained in this study is also expected to play an important role in the field of soil remediation, especially for the site soils left in urban areas by relocated factories.