Mohamad Fakih a,1, Mélanie Davranche a,⁎, Aline Dia a, Bernd Nowack b,c, Guillaume Morin c,d, Patrice Petitjean a, Xavier Châtellier a, Gérard Gruau a
a Geosciences UMR 6118, Université de Rennes 1, Campus de Beaulieu, 263 Av. du Général Leclerc, 35042 Rennes cedex, France
b EMPA, Swiss Federal Laboratories for Materials Testing and Research, 5Technology and Society, Lerchenfeldstrasse 5, 9014 St. Gallen, Switzerland
c Institute of Terrestrial Ecosystems, ETH Zurich, Universitaetstrasse 16, 8092 Zurich, Switzerland
d CNRS-UMR 7590, Institut de Minéralogie et Physique des Milieux Condensés IMPMC, University of Paris 6, University of Paris 7 — Campus Boucicaut, 140 rue de Lourmel 75015 Paris, France
Chemical Geology 259 (2009) 290–303
Polymer slides covered by synthetic As-spiked ferrihydrite (As-Fh) or As-spiked lepidocrocite (As-Lp) were
inserted into an organic-rich wetland soil in non conventional columns system under anaerobic conditions.
Slides were recovered after different periods of time to evaluate (i) the impact of (bio)reduction on both Feoxide dissolution and secondary mineral precipitation and, (ii) the subsequent effects on As mobility. The calculated Fe dissolution rates for As-Fh and As-Lp were 2.02 ·10−9 and 1.92 ·10−9 mol Fem−2 s−1, respectively, and were higher than what has been commonly reported in laboratory studies. Important bacterial colonization and occurrence of biofilm suggest the presence of biologically mediated processes. The newly formed minerals were mostly composed of Fe-sulphides. Fe(II) complexation by organic molecules in solution likely prevented formation of secondary Fe(II, III)-rich minerals. The relative proportion of As(III) increased with time on the As-Fh slides, and was combined with a decrease of the Fe/As ratio, suggesting a partial adsorption of As(III) onto minerals. By contrast, for lepidocrocite, the Fe/As ratio increased, suggesting that As(III) was less readsorbed due the lower available site number and the deletion of As adsorption sites on the reduced lepidocrocite surface. Reduction and subsequent As sequestration appeared to result from a coupled biotic–abiotic reaction pathway in which Fe or As reducing-bacteria allowed the reduction of As(V) to As(III).
a Geosciences UMR 6118, Université de Rennes 1, Campus de Beaulieu, 263 Av. du Général Leclerc, 35042 Rennes cedex, France
b EMPA, Swiss Federal Laboratories for Materials Testing and Research, 5Technology and Society, Lerchenfeldstrasse 5, 9014 St. Gallen, Switzerland
c Institute of Terrestrial Ecosystems, ETH Zurich, Universitaetstrasse 16, 8092 Zurich, Switzerland
d CNRS-UMR 7590, Institut de Minéralogie et Physique des Milieux Condensés IMPMC, University of Paris 6, University of Paris 7 — Campus Boucicaut, 140 rue de Lourmel 75015 Paris, France
Chemical Geology 259 (2009) 290–303
Polymer slides covered by synthetic As-spiked ferrihydrite (As-Fh) or As-spiked lepidocrocite (As-Lp) were
inserted into an organic-rich wetland soil in non conventional columns system under anaerobic conditions.
Slides were recovered after different periods of time to evaluate (i) the impact of (bio)reduction on both Feoxide dissolution and secondary mineral precipitation and, (ii) the subsequent effects on As mobility. The calculated Fe dissolution rates for As-Fh and As-Lp were 2.02 ·10−9 and 1.92 ·10−9 mol Fem−2 s−1, respectively, and were higher than what has been commonly reported in laboratory studies. Important bacterial colonization and occurrence of biofilm suggest the presence of biologically mediated processes. The newly formed minerals were mostly composed of Fe-sulphides. Fe(II) complexation by organic molecules in solution likely prevented formation of secondary Fe(II, III)-rich minerals. The relative proportion of As(III) increased with time on the As-Fh slides, and was combined with a decrease of the Fe/As ratio, suggesting a partial adsorption of As(III) onto minerals. By contrast, for lepidocrocite, the Fe/As ratio increased, suggesting that As(III) was less readsorbed due the lower available site number and the deletion of As adsorption sites on the reduced lepidocrocite surface. Reduction and subsequent As sequestration appeared to result from a coupled biotic–abiotic reaction pathway in which Fe or As reducing-bacteria allowed the reduction of As(V) to As(III).
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