Selenium speciation in acidic environmental samples: Application to acid rain-soil interaction at Mount Etna volcano

► Precipitation of Al and Fe phases can hamper selenium speciation analyses. ► In a ammonium citrate buffer at pH = 3 aqueous Fe and Al are thermodynamically stable. ► Selenate and selenite could be separated in 10 min and separated from bromine. ► Selenium enriched soil leachates from Etna indicate the dominance of selenate. ► The competitive behavior with sulfate present in acid rain mobilizes Se.