Natural Arsenic Attenuation via Metal Arsenate Precipitation in Soils Contaminated with Metallurgical Wastes: I. Wet Chemical and Thermodynamic Evidences

• Published in: Aquatic geochemistry 2010-03, Vol.16 (2), p.225-250
• Main Authors: Villalobos, M, García-Payne, D. G, López-Zepeda, J. L, Ceniceros-Gómez, A. E, Gutiérrez-Ruiz, M. E
• Format: Article
• Language: English
• Subjects: Anthropogenic factors; Arsenates; Arsenic; Contaminants; Earth and Environmental Science; Earth Sciences; Environmental cleanup; Geochemistry; Heavy metals; Hydrogeology; Hydrology/Water Resources; Lead; Metal industry wastes; Original Paper; Simulation; Soil contamination; Water Quality/Water Pollution
• ISSN: 1380-6165; 1573-1421
• DOI: 10.1007/s10498-009-9065-4

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.