Arsenic speciation and trace element analysis of the volcanic río Agrio and the geothermal waters of Copahue, Argentina

► Application of a novel field-based method for the separation of arsenic species in a volcanic surface water system. ► First arsenic speciation data for volcanic systems in the Andes (iAsV, iAsIII, MAV, DMAV). ► Total arsenic levels along the río Agrio ranged from < 0.2-3783 μg/l AsT. ► Arsenic species distribution shows a statistically significant correlation with redox potential, Fe, Mn and V levels.