Identification of the As-bearing phases in fresh volcanic Andean ashes

BIA, GONZALO; BORGNINO, LAURA; GARCIA, MG; , DM GAIERO, ...

One Century of the Discovery of Arsenicosis in Latin America (1914-2014): As 2014 - Proceedings of the 5th International Congress on Arsenic in the Environment

CRC Press/Balkama

Año: 2014; p. 87 - 89

The sources and dynamics of arsenic in fresh volcanic ashes collected during the eruptions ofHudson (1991) and Puyehue (2011) volcanos, have been studied. The chemical and mineralogicalcompositions of both volcanic ashes were analyzed by ICP/OES, DRX, and SEM-EDS. Batch experimentswere conducted to evaluate the kinetics of the arsenic release under variable pH. Results indicate that therelease is enhanced under both, acidic and alkaline conditions. Besides, the positive significant linear trendfound between Fe and As concentrations in the leachates suggests that arsenopyrite or/and its alterationproduct scorodite is one important As-bearing phase present in the ash samples. This phase would be the mainresponsible of the As release under acidic conditions. At higher pH, other mechanisms are involved:desorption from Fe(hydr)oxide coatings (at neutral to slightly alkaline conditions) and dissolution of botharsenopyrite and volcanic glass at pH higher than 9.