Arsenic-bearing phases in South Andean volcanic ashes: Implications for As mobility in aquatic environments

 

Autores
Bia, Gonzalo Luis; Borgnino Bianchi, Laura Carolina; Gaiero, Diego Marcelo; Garcia, Maria Gabriela
Tipo de recurso
artículo
Estado
Versión publicada
Año de publicación
2015
País
Argentina
Institución
Consejo Nacional de Investigaciones Científicas y Técnicas
Repositorio
CONICET Digital (CONICET)
Descripción
Three samples of volcanic ashes collected after eruptions of the volcanos Hudson in 1991, Chaitén in 2008 and Puyehue in 2011 were analyzed in order to define the solid speciation of arsenic and the dynamics of its release to the aqueous phase. The bulk chemical and mineralogical characterization of the samples was performed by ICP/OES, DRX, and SEM/EDS analyses. The chemical composition of the near surface region (first 2-10. nm), along with the As and Fe solid speciation was performed by XPS. Batch experiments were conducted to evaluate the kinetics of the arsenic release under variable pH conditions. The integrated analysis of these data indicates that arsenic compounds are concentrated onto the ash surface in the form of As(III)-S and As(V)-O species. The As(III) species have been assigned to arsenian pyrite, while As(V)-O compounds have been assigned to adsorbed arsenate ions or Fe arsenate salts precipitated as thin coatings.Although the main As carrier in the studied volcanic ashes is Al-silicate glass, this phase is stable at the neutral pH that dominates the aqueous reservoirs of the area affected by ashfall. Thus, its contribution to the pool of dissolved arsenic is minor. Higher contributions are clearly associated with the more mobile As species that concentrate onto the surface of Al-silicate glass. This more available arsenic represents less than 6% of the total measured arsenic.
Idioma
inglés
OAI Identifier
oai:ri.conicet.gov.ar:11336/37629
Enlace del recurso
http://hdl.handle.net/11336/37629
Nivel de acceso
Acceso abierto
Materia
AL-SILICATE GLASS
AS SOLID SPECIATION
SOUTH AMERICA
XPS
Meteorología y Ciencias Atmosféricas
Ciencias de la Tierra y relacionadas con el Medio Ambiente
CIENCIAS NATURALES Y EXACTAS