废弃铬盐厂土壤中铬的赋存特征及异位淋洗修复可行性研究

土壤理化性质、污染物的分布及赋存特征是土壤异位淋洗技术是否可行的关键依据。以西北某废弃铬盐厂铬污染场地土壤作为研究对象，测定了土壤基本理化参数及各粒径污染物的浓度，探究总铬和六价铬在不同粒径土壤中的分布特征，并通过铬的赋存形态分析确定清水作为淋洗剂，开展异位清水淋洗实验。结果表明：供试土壤粗颗粒物料（粒径分别为：>9.50 mm、2.00~9.50 mm、0.841~2.00 mm及0.25~0.841 mm）占土壤总质量的比例达到93.36%，总铬和六价铬污染物富集于土壤细颗粒（粒径-1，达到修复标准要求。

Research on occurrence characteristics of Chromium in soils and feasibility study of ex-situ soil washing for an abandoned chrome chemicals manufacturing facility

The physicochemical properties of soil, its distribution characteristics and the speciation of contaminants are the key factors for assessing the feasibility of the ex-situ soil washing technology. Soil samples were collected from an abandoned chrome chemicals manufacturing facility in Northwest China in order to study the distribution characteristics of total chromium and hexavalent chromium within the different soil particle size fractions, based on the test results of the physicochemical properties of soil and the associated contamination concentration for each particle size fraction. Based on the analysis of chromium speciation, water was selected as the soil washing reagent and the bench-scale test of ex-situ soil washing was subsequently developed. The results showed that the mass ratio of coarse particles (i.e., >9.50 mm, 2.00-9.50 mm, 0.841-2.00 mm and 0.25-0.841 mm, combined) reached 93.36% and the total chromium as well as the hexavalent chromium accumulated on fine particles (<0.25 mm). Moreover, both the water-soluble and the weak acid-soluble fractions of total chromium in the coarse particle fractions were over 50%. After washing with deionized water, the removal efficiencies of total chromium and hexavalent chromium exceeded 60% and 80%, respectively. The concentrations of hexavalent chromium in all the soil particle size fractions were below 30 mg/kg, which met the standard requirement for remediation.