Mobilization of arsenic in aquifers from the Datong Basin, China: Evidence from geochemical and iron isotopic data

► Iron isotopic study was performed to identify the mechanism of As mobilization in aquifer system. ► Transformation between crystalline Fe(III) and poor crystalline Fe phase has occurred. ► There is a significant difference in As contents in crystalline Fe(III) and HCl-extracted Fe phases. ► The transformation of different Fe phases can be used to explain the As enrichment in groundwater.