Identification of arsenic solid species in abandoned mine wastes from the Argentina Puna using X-ray absorption spectroscopy

NIEVA N.E.; BORGNINO, L.; GARCÍA M. G

Estocolmo

Congreso; 6th International Congress on Arsenic in the Environment; 2016

The As solid speciation of the abandoned sulfide minewastes accumulated in La Concordia mine, Argentina Puna is analyzed. Samples werecollected from the exposed walls of an oxidation profile formed in one of the tailingdams. Mineralogy was characterized by XRD and SEM/EDS. X-ray absorption finestructure spectroscopy (XAFS) was used to determine the arsenic oxidation state.The primary sources are As-bearing sulfides, such as arsenian pyrite and arsenopyrite.As-jarosite and scorodite are the more abundant secondary As-bearing minerals. X-rayabsorption near edge structure (XANES) analysis indicates that As+5is the dominant oxidation state in the entire oxidation profile but minorproportions of As+3 are also observed in the bottom saturated layers.The in-depth distribution of the As redox species reveal that after 30 years ofexposure, oxidation has affected almost the entire sedimentary column,eventhough signs of anoxic conditions are macroscopically observed.