title: Selenium speciation in acidic environmental samples: application to acid rain-soil interaction at Mount Etna volcano.
abstract: Speciation plays a crucial role in elemental mobility. However, trace level selenium (Se) speciation analyses in aqueous samples from acidic environments are hampered due to adsorption of the analytes (i.e. selenate, selenite) on precipitates. Such solid phases can form during pH adaptation up till now necessary for chromatographic separation. Thermodynamic calculations in this study predicted that a pH<4 is needed to prevent precipitation of Al and Fe phases. Therefore, a speciation method with a low pH eluent that matches the natural sample pH of acid rain-soil interaction samples from Etna volcano was developed. With a mobile phase containing 20mM ammonium citrate at pH 3, selenate and selenite could be separated in different acidic media (spiked water, rain, soil leachates) in <10 min with a LOQ of 0.2 μg L(-1) using (78)Se for detection. Applying this speciation analysis to study acid rain-soil interaction using synthetic rain based on H(2)SO(4) and soil samples collected at the flanks of Etna volcano demonstrated the dominance of selenate over selenite in leachates from samples collected close to the volcanic craters. This suggests that competitive behavior with sulfate present in acid rain might be a key factor in Se mobilization. The developed speciation method can significantly contribute to understand Se cycling in acidic, Al/Fe rich environments.
authors.affiliation: Department of Chemistry, University of Girona, Campus de Montilivi s/n, 17071 Girona, Spain. geerke.floor@aquatrain.eu
authors.forename: Geerke H
authors.initials: GH
authors.lastname: Floor
authors.forename: Mònica
authors.initials: M
authors.lastname: Iglesías
authors.forename: Gabriela
authors.initials: G
authors.lastname: Román-Ross
authors.forename: Philippe F X
authors.initials: PF
authors.lastname: Corvini
authors.forename: Markus
authors.initials: M
authors.lastname: Lenz
mesh_terms: D015258:Acid Rain; D002851:Chromatography, High Pressure Liquid; D019343:Citric Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry; D013058:Mass Spectrometry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D064586:Selenic Acid; D018036:Selenium Compounds / Q000737:chemistry*; D018038:Sodium Selenite / Q000737:chemistry*; D012987:Soil; D013816:Thermodynamics; D018707:Volcanic Eruptions
chemical_list: D015258:Acid Rain; D000644:Quaternary Ammonium Compounds; D018036:Selenium Compounds; D012987:Soil; D019343:Citric Acid; C481046:ammonium citrate; D007501:Iron; D018038:Sodium Selenite; D064586:Selenic Acid