title: Simultaneous Nitrite/Nitrate Imagery at Millimeter Scale through the Water-Sediment Interface.
abstract: The present study describes new procedures to obtain at millimeter resolution the spatial distribution of nitrite and nitrate in porewaters, combining diffusive equilibrium in thin films (DET), colorimetry and hyperspectral imagery. Nitrite distribution can be easily achieved by adapting the well-known colorimetric method from Griess (1879) and using a common flatbed scanner with a limit of detection about 1.7 μmol L(-1). Nitrate distribution can be obtained after reduction into nitrite by a vanadium chloride reagent. However, the concentration of vanadium chloride used in this protocol brings coloration with a wide spectral signature that creates interference only deconvolvable by imaging treatment from an entire visible spectrum for each pixel (spectral analysis). This can be achieved by hyperspectral imaging. The protocol retained in the present study allows obtaining a nitrite/nitrate image with micromolar limit of detection. The methods were applied in sediments from the Loire Estuary after different treatments and allowed to precisely describe two-dimensional millimeter features. The present technique adds to the combination of gel-colorimetry and hyperspectral imagery a very promising new application of wide interest for environmental issues in the context of early diagenesis and benthic fluxes.
authors.affiliation: Université d'Angers, LPG-BIAF, UMR CNRS 6112, 49045 Angers Cedex, France.
authors.forename: E
authors.initials: E
authors.lastname: Metzger
authors.affiliation: Université d'Angers, LPG-BIAF, UMR CNRS 6112, 49045 Angers Cedex, France.|Ifremer, LBCM, Rue de l'Ile d'Yeu, 44300 Nantes, France.
authors.forename: A
authors.initials: A
authors.lastname: Thibault de Chanvalon
authors.affiliation: Université d'Angers, LPG-BIAF, UMR CNRS 6112, 49045 Angers Cedex, France.|University of West Florida, CEDB, 11000 University Parkway, Pensacola, Florida 32514 United States.
authors.forename: F
authors.initials: F
authors.lastname: Cesbron
authors.affiliation: Université d'Angers, LPG-BIAF, UMR CNRS 6112, 49045 Angers Cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Barbe
authors.affiliation: Université de Nantes, LPG-N, UMR CNRS 6112, 44322 Nantes, France.
authors.forename: P
authors.initials: P
authors.lastname: Launeau
authors.affiliation: Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ. Paris Diderot, UMR 7154 CNRS, 75005 Paris, France.
authors.forename: D
authors.initials: D
authors.lastname: Jézéquel
authors.affiliation: Université d'Angers, LPG-BIAF, UMR CNRS 6112, 49045 Angers Cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Mouret
mesh_terms: D003124:Colorimetry; D009566:Nitrates; D009573:Nitrites; D014867:Water; D014874:Water Pollutants, Chemical
chemical_list: D009566:Nitrates; D009573:Nitrites; D014874:Water Pollutants, Chemical; D014867:Water