Natural Arsenic Attenuation via Metal Arsenate Precipitation in Soils Contaminated with Metallurgical Wastes: I. Wet Chemical and Thermodynamic Evidences |
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| Authors: | M Villalobos D G García-Payne J L López-Zepeda A E Ceniceros-Gómez and M E Gutiérrez-Ruiz |
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| Institution: | (1) Environmental Bio-Geochemistry Group, LAFQA, Instituto de Geograf?a, Universidad Nacional Aut?noma de M?xico (UNAM), Coyoac?n, D.F., 04510, Mexico |
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| Abstract: | Arsenic from natural and anthropogenic sources is a worldwide contaminant of aqueous environments, such as groundwater and
soils. The present investigation was performed on Mexican soils contaminated with residues from metallurgical processes that
have shown a natural As attenuation. Experimental aqueous arsenic extractions in these were successfully simulated for almost
half of the soil samples using a database updated for all known metal arsenate formation constants, revealing the predominance
of solubility-controlled As mobility via Pb, mixed Pb–Cu, and Ca arsenate solid formation. The relatively low total Fe/As
ratios (2–13 w/w) present in the soils studied, together with the high and equivalent contents of As, Pb, and Cu in these,
favor the precipitation process over As(V) adsorption to Fe oxides, despite a 2% average Fe content in the soils studied.
Under these conditions bicarbonate was found to be a highly unsuitable extractant due to its indirect As release from the
solid arsenates, via heavy metal carbonate precipitation processes. |
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