A Single Chemical Extraction Scheme for the Simultaneous Evaluation of the Potential Mobility of a Metalloid (As) and Metallic Elements (Cd, Cu, Ni, Pb, Zn) in Contaminated Soils and Mine Wastes

摘要

The total concentration of toxic chemical elements present in contaminated soils and mine wastes does not provide reliable information about the risk they present to Man and the Environment. Realistic assessments imply determining the fraction of total pollutant load susceptible to be solubilized and thus potentially transferred to the hydrocycle and the biosphere. Chemical extraction is the most commonly used method to reach this objective. Here we investigate two of the classical methods of sequential extraction, the first developed for cationic metallic elements (Tessier et al., 1979), the second for the oxyanionic phosphorus, a chemical analogue of arsenic (Woolson et al., 1983) and we propose a single protocol capable of simultaneous giving useful information about the reactivity of both cationic and anionic pollutants (often present together in contamination due to mining and smelting activities or heavy chemical industry). If the method of Tessier et al. (1979) is used for arsenic, it underestimates its potential mobility. The method we propose does not provide direct clues about the geochemical associations of the toxic elements in the contaminated solids but it gives instead information about (a) the potentially mobile fraction of these elements and (b) their geochemical behavior in the presence of a large range of physical-chemical conditions (acidic, alkaline, oxidizing, reducing), data of interest for remediation measures.