Mechanisms of fluoride release in sediments of Argentina's central region

► Fluvial and loess sediments of Central Argentina release high fluoride concentrations. ► Fluoride release depends on pH and dominant cation in the solution. ► Dissolution of a Ca/F-bearing phase is the primary source of fluoride at acidic pH (< 6). ► Desorption from Fe/Mn(hydr)oxides occurs under alkaline conditions.