title: X-ray absorption fine structure evidence for amorphous zinc sulfide as a major zinc species in suspended matter from the Seine River downstream of Paris, Ile-de-France, France.
abstract: Zinc is one of the most widespread trace metals (TMs) in Earth surface environments and is the most concentrated TM in the downstream section of the Seine River (France) due to significant anthropogenic input from the Paris conurbation. In order to better identify the sources and cycling processes of Zn in this River basin, we investigated seasonal and spatial variations of Zn speciation in suspended particulate matter (SPM) in the oxic water column of the Seine River from upstream to downstream of Paris using synchrotron-based extend X-ray absorption fine structure (EXAFS) spectroscopy at the Zn K-edge. First-neighbor contributions to the EXAFS were analyzed in SPM samples, dried and stored under a dry nitrogen atmosphere or under an ambient oxygenated atmosphere. We found a sulfur first coordination environment around Zn (in the form of amorphous zinc sulfide) in the raw SPM samples stored under dry nitrogen vs an oxygen first coordination environment around Zn in the samples stored in an oxygenated atmosphere. These findings are supported by scanning electron microscopy and energy dispersive X-ray spectrometry observations. Linear combination fitting of the EXAFS data for SPM samples, using a large set of EXAFS spectra of Zn model compounds, indicates dramatic changes in the Zn speciation from upstream to downstream of Paris, with amorphous ZnS particles becoming dominant dowstream. In contrast, Zn species associated with calcite (either adsorbed or incorporated in the structure) are dominant upstream. Other Zn species representing about half of the Zn pool in the SPM consist of Zn-sorbed on iron oxyhydroxides (ferrihydrite and goethite) and, to a lesser extent, Zn-Al layered double hydroxides, Zn incorporated in dioctahedral layers of clay minerals and Zn sorbed to amorphous silica. Our results highlight the importance of preserving the oxidation state in TM speciation studies when sampling suspended matter, even in an oxic water column.
authors.affiliation: Laboratoire des Sciences du Climat et de l'Environnement (LSCE/IPSL), UMR 1572 (CEA/CNRS/UVSQ), Domaine du CNRS, Gif-sur-Yvette, France.
authors.forename: Cindy
authors.initials: C
authors.lastname: Priadi
authors.forename: Pierre
authors.initials: P
authors.lastname: Le Pape
authors.forename: Guillaume
authors.initials: G
authors.lastname: Morin
authors.forename: Sophie
authors.initials: S
authors.lastname: Ayrault
authors.forename: Fabien
authors.initials: F
authors.lastname: Maillot
authors.forename: Farid
authors.initials: F
authors.lastname: Juillot
authors.forename: Rebecca
authors.initials: R
authors.lastname: Hochreutener
authors.forename: Isabelle
authors.initials: I
authors.lastname: Llorens
authors.forename: Denis
authors.initials: D
authors.lastname: Testemale
authors.forename: Olivier
authors.initials: O
authors.lastname: Proux
authors.forename: Gordon E
authors.initials: GE
authors.lastname: Brown
mesh_terms: D004583:Electrons; D005583:Fourier Analysis; D019015:Geologic Sediments / Q000737:chemistry; D016014:Linear Models; D008855:Microscopy, Electron, Scanning; D010100:Oxygen; D010297:Paris; D052638:Particulate Matter / Q000737:chemistry*; D045483:Rivers / Q000737:chemistry*; D013440:Sulfides / Q000032:analysis* / Q000737:chemistry*; D013535:Suspensions; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical; D056928:X-Ray Absorption Spectroscopy / Q000379:methods*; D015032:Zinc / Q000032:analysis*; D017967:Zinc Compounds / Q000032:analysis* / Q000737:chemistry*
chemical_list: D052638:Particulate Matter; D013440:Sulfides; D013535:Suspensions; D014874:Water Pollutants, Chemical; D017967:Zinc Compounds; D014867:Water; D015032:Zinc; C031238:zinc sulfide; D010100:Oxygen