Applications of data on the mobility of heavy metals in contaminated soil to the definition of site-specific remediation criteria

Abstract

More than a decade of research on the fractionation of heavy metals in soil has led scientists and engineers to the conclusion that the mobility of heavy metals can be defined by the relative sensitivity of their solid species to environmental stresses. The following paper presents a procedure to obtain the fractionation of heavy metals during the acidification of the soil and discusses the use such data. The procedure used combines an acid–base titration of the soil with the Tessier scheme of sequential chemical extractions (SCEs). The soil was strongly buffered against acidification by the dissolution of solid carbonates. Cadmium and zinc were nevertheless significantly dissolved by acidification from pH 8 to pH 5. All other heavy metals were dissolved once pH 5 was attained. The most soluble heavy metals were those that had formed less stable acid-soluble and reducible solid species. These results are used as an example to demonstrate the importance of knowing the buffering capacity of the soil and the fractionation of heavy metals to obtain a more rigorous assessment of the mobility of heavy metals and to determine site-specific remediation criteria. Key words: contaminated soil, heavy metals, mobility, sequential chemical extractions, buffering capacity, remediation criteria.