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

GONZAL BIA; MA GABRIELA GARCIA; LAURA BORGNINO

In book: 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/Balkema. Taylor and Francis Group

Lugar: Leiden, The Netherlands; Año: 2014; p. 225 - 226

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