title: The impact of oscillating redox conditions: arsenic immobilisation in contaminated calcareous floodplain soils.
abstract: Arsenic contamination of floodplain soils is extensive and additional fresh arsenic inputs to the pedosphere from human activities are ongoing. We investigate the cumulative effects of repetitive soil redox cycles, which occur naturally during flooding and draining, on a calcareous fluvisol, the native microbial community and arsenic mobility following a simulated contamination event. We show through bioreactor experiments, spectroscopic techniques and modelling that repetitive redox cycling can decrease arsenic mobility during reducing conditions by up to 45%. Phylogenetic and functional analyses of the microbial community indicate that iron cycling is a key driver of observed changes to solution chemistry. We discuss probable mechanisms responsible for the arsenic immobilisation observed in-situ. The proposed mechanisms include, decreased heterotrophic iron reduction due to the depletion of labile particulate organic matter (POM), increases to the proportion of co-precipitated vs. aqueous or sorbed arsenic with α-FeOOH/Fe(OH)3 and potential precipitation of amorphous ferric arsenate.
authors.affiliation: Environmental Geochemistry Group, ISTerre, University of Grenoble I, B. P. 53, 38041 Grenoble, France. chris.parsons85@gmail.com
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Parsons
authors.forename: Raoul-Marie
authors.initials: RM
authors.lastname: Couture
authors.forename: Enoma O
authors.initials: EO
authors.lastname: Omoregie
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Bardelli
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Greneche
authors.forename: Gabriela
authors.initials: G
authors.lastname: Roman-Ross
authors.forename: Laurent
authors.initials: L
authors.lastname: Charlet
mesh_terms: D001151:Arsenic / Q000032:analysis / Q000737:chemistry*; D019149:Bioreactors; D002119:Calcium Carbonate / Q000032:analysis / Q000737:chemistry; D055868:Floods; D010084:Oxidation-Reduction; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry*
chemical_list: D012987:Soil; D012989:Soil Pollutants; D002119:Calcium Carbonate; D001151:Arsenic