More than redox, biological organic ligands control iron isotope fractionation in the riparian wetland

Type Article
Date 2021-12
Language English
Author(s) Lotfi-Kalahroodi Elaheh1, Pierson-Wickmann Anne-Catherine1, Rouxel Olivier2, Marsac Rémi1, Bouhnik-Le Coz Martine1, Hanna Khalil3, Davranche Mélanie1
Affiliation(s) 1 : Univ. Rennes, CNRS, Géosciences Rennes - UMR 6118, 35000, Rennes, France
2 : IFREMER, Unité de Géosciences Marines, 29280, Plouzané, France
3 : Univ. Rennes, Ecole Nationale Supérieure de Chimie de Rennes, CNRS ISCR UMR6226, 35000, Rennes, France
Source Scientific Reports (2045-2322) (Springer Science and Business Media LLC), 2021-12 , Vol. 11 , N. 1 , P. 1933 (12p.)
DOI 10.1038/s41598-021-81494-z

Although redox reactions are recognized to fractionate iron (Fe) isotopes, the dominant mechanisms controlling the Fe isotope fractionation and notably the role of organic matter (OM) are still debated. Here, we demonstrate how binding to organic ligands governs Fe isotope fractionation beyond that arising from redox reactions. The reductive biodissolution of soil Fe(III) enriched the solution in light Fe isotopes, whereas, with the extended reduction, the preferential binding of heavy Fe isotopes to large biological organic ligands enriched the solution in heavy Fe isotopes. Under oxic conditions, the aggregation/sedimentation of Fe(III) nano-oxides with OM resulted in an initial enrichment of the solution in light Fe isotopes. However, heavy Fe isotopes progressively dominate the solution composition in response to their binding with large biologically-derived organic ligands. Confronted with field data, these results demonstrate that Fe isotope systematics in wetlands are controlled by the OM flux, masking Fe isotope fractionation arising from redox reactions. This work sheds light on an overseen aspect of Fe isotopic fractionation and calls for a reevaluation of the parameters controlling the Fe isotopes fractionation to clarify the interpretation of the Fe isotopic signature.

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Lotfi-Kalahroodi Elaheh, Pierson-Wickmann Anne-Catherine, Rouxel Olivier, Marsac Rémi, Bouhnik-Le Coz Martine, Hanna Khalil, Davranche Mélanie (2021). More than redox, biological organic ligands control iron isotope fractionation in the riparian wetland. Scientific Reports, 11(1), 1933 (12p.). Publisher's official version : , Open Access version :