Chromium is a heavy element that is present in various industrial activities such as electroplating, welding, foundries and tanneries. This metal may occur naturally in the environment in the forms of tri- and hexavalent chromium, the former being more stable, less toxic, and essential to human nutrition in trace concentrations. The latter form, hexavalent, is toxic, carcinogenic and strongly oxidizing, as well as highly mobile in soil. Conventional treatments of chromium-contaminated soils and aquatic environments are based mainly on the methods of excavation or pumping out of the contaminated material, the addition of chemical reducing agents, precipitation followed by sedimentation, ion exchange, and adsorption. A highly promising technique which has recently been tested is plant-based soil remediation, known as phytoremediation. In this study, we intend to analyze the interaction of Cr(III) and (IV) with soil minerals, before and after phytoremediation treatment, by applying the sequential extraction procedure. This analysis is expected to reveal the geochemical distribution of Cr(III) and (VI) in the main phases found in soil (soluble, exchangeable, associated with carbonates and sulfides, bound to iron and manganese oxides, to organic matter, and also attached to the structures of certain minerals), and to allow for an assessment of the efficiency of phytoremediation as an alternative and sustainable method of remediation of soils contaminated with Cr(VI).
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