title: Interactions between natural organic matter, sulfur, arsenic and iron oxides in re-oxidation compounds within riparian wetlands: nanoSIMS and X-ray adsorption spectroscopy evidences.
abstract: Arsenic (As) is a toxic and ubiquitous element which can be responsible for severe health problems. Recently, Nano-scale Secondary Ions Mass Spectrometry (nanoSIMS) analysis has been used to map organomineral assemblages. Here, we present a method adapted from Belzile et al. (1989) to collect freshly precipitated compounds of the re-oxidation period in a natural wetland environment using a polytetrafluoroethylene (PTFE) sheet scavenger. This method provides information on the bulk samples and on the specific interactions between metals (i.e. As) and the natural organic matter (NOM). Our method allows producing nanoSIMS imaging on natural colloid precipitates, including (75)As(-), (56)Fe(16)O(-), sulfur ((32)S(-)) and organic matter ((12)C(14)N) and to measure X-ray adsorption of sulfur (S) K-edge. A first statistical treatment on the nanoSIMS images highlights two main colocalizations: (1) (12)C(14)N(-), (32)S(-), (56)Fe(16)O(-) and (75)As(-), and (2) (12)C(14)N(-), (32)S(-) and (75)As(-). Principal component analyses (PCAs) support the importance of sulfur in the two main colocalizations firstly evidenced. The first component explains 70% of the variance in the distribution of the elements and is highly correlated with the presence of (32)S(-). The second component explains 20% of the variance and is highly correlated with the presence of (12)C(14)N(-). The X-ray adsorption near edge spectroscopy (XANES) on sulfur speciation provides a quantification of the organic (55%) and inorganic (45%) sulfur compositions. The co-existence of reduced and oxidized S forms might be attributed to a slow NOM kinetic oxidation process. Thus, a direct interaction between As and NOM through sulfur groups might be possible.
authors.affiliation: Géosciences Rennes, Université Rennes 1, CNRS UMR 6118, Av. General Leclerc, 35042 Rennes Cedex, France. Electronic address: maya.al-sid-cheikh@univ-rennes1.fr.
authors.forename: Maya
authors.initials: M
authors.lastname: Al-Sid-Cheikh
authors.affiliation: Géosciences Rennes, Université Rennes 1, CNRS UMR 6118, Av. General Leclerc, 35042 Rennes Cedex, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Pédrot
authors.affiliation: Géosciences Rennes, Université Rennes 1, CNRS UMR 6118, Av. General Leclerc, 35042 Rennes Cedex, France.
authors.forename: Aline
authors.initials: A
authors.lastname: Dia
authors.affiliation: Géosciences Rennes, Université Rennes 1, CNRS UMR 6118, Av. General Leclerc, 35042 Rennes Cedex, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Guenet
authors.affiliation: Synchrotron Soleil, L'Orme des Merisiers, Saint Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Vantelon
authors.affiliation: Géosciences Rennes, Université Rennes 1, CNRS UMR 6118, Av. General Leclerc, 35042 Rennes Cedex, France.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Davranche
authors.affiliation: Géosciences Rennes, Université Rennes 1, CNRS UMR 6118, Av. General Leclerc, 35042 Rennes Cedex, France.
authors.forename: Gérard
authors.initials: G
authors.lastname: Gruau
authors.affiliation: NanoSIMS Platform, Université Rennes 1, CNRS UMR 6118, Av. General Leclerc, 35042 Rennes Cedex, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Delhaye
mesh_terms: D000327:Adsorption; D001151:Arsenic / Q000032:analysis / Q000737:chemistry*; D005290:Ferric Compounds / Q000032:analysis / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis*; D007700:Kinetics; D008956:Models, Chemical; D010084:Oxidation-Reduction; D013455:Sulfur / Q000032:analysis / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*; D053833:Wetlands; D056928:X-Ray Absorption Spectroscopy
chemical_list: D005290:Ferric Compounds; D006812:Humic Substances; D014874:Water Pollutants, Chemical; C000499:ferric oxide; D013455:Sulfur; D001151:Arsenic
keywords: Arsenic; Iron oxid; NanoSIMS; Natural organic matter; Riparian wetland; Sulfur; X-ray adsoprtion