title: Natural Hg isotopic composition of different Hg compounds in mammal tissues as a proxy for in vivo breakdown of toxic methylmercury.
abstract: In the last decade, specific attention has been paid to total mercury (HgT) stable isotopic composition, especially in natural samples such as aquatic organisms, due to its potential to track the cycle of this toxic element in the environment. Here, we investigated Hg Compound Specific stable Isotopic Composition (CSIC) of natural inorganic Hg (iHg) and methylmercury (MMHg) in various tissues of aquatic mammals (Beluga whale from the Arctic marine environment and seals from the freshwater lake Baikal, Russia). In seals' organs the variation in mass dependent fractionation (MDF, δ(202)Hg) for total Hg was significantly correlated to the respective fraction of iHg and MMHg compounds, with MMHg being enriched by ∼ 3‰ in heavier isotopes relative to iHg. On the other hand, we observe insignificant variation in Hg mass independent isotope fractionation (MIF, Δ(199)Hg) among iHg and MMHg in all organs for the same mammal species and MMHg in prey items. MIF signatures suggest that both MMHg and iHg in aquatic mammals have the same origin (i.e., MMHg from food), and are representative of Hg photochemistry in the water column of the mammal ecosystem. MDF signatures of Hg compounds indicate that MMHg is demethylated in vivo before being stored in the muscle, and the iHg formed is stored in the liver, and to a lesser extent in the kidney, before excretion. Thus, Hg CSIC analysis in mammals can be a powerful tool for tracing the metabolic response to Hg exposure.
authors.affiliation: Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut des Sciences Analytiques et de Physico-chimie pour l'Environnement et les Matériaux, IPREM UMR-5254, CNRS-UPPA, Hélioparc, 2 Avenue du Président Pierre Angot, Pau, 64053, France. david.amouroux@univ-pau.fr.
authors.forename: Vincent
authors.initials: V
authors.lastname: Perrot
authors.affiliation: Laboratoire Géosciences Environnement Toulouse, Observatoire Midi-Pyrénées CNRS-IRD-Université de Toulouse 3, 14 avenue Edouard Belin, Toulouse, 31400, France.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Masbou
authors.affiliation: Laboratory of Geochemical Mapping and Monitoring, Institute of Geochemistry SB RAS, 1A Favorskogo Street, PB-304, Irkutsk, 664033, Russia.
authors.forename: Mikhail V
authors.initials: MV
authors.lastname: Pastukhov
authors.affiliation: Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut des Sciences Analytiques et de Physico-chimie pour l'Environnement et les Matériaux, IPREM UMR-5254, CNRS-UPPA, Hélioparc, 2 Avenue du Président Pierre Angot, Pau, 64053, France. david.amouroux@univ-pau.fr.
authors.forename: Vladimir N
authors.initials: VN
authors.lastname: Epov
authors.affiliation: Laboratoire Géosciences Environnement Toulouse, Observatoire Midi-Pyrénées CNRS-IRD-Université de Toulouse 3, 14 avenue Edouard Belin, Toulouse, 31400, France.
authors.forename: David
authors.initials: D
authors.lastname: Point
authors.affiliation: Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut des Sciences Analytiques et de Physico-chimie pour l'Environnement et les Matériaux, IPREM UMR-5254, CNRS-UPPA, Hélioparc, 2 Avenue du Président Pierre Angot, Pau, 64053, France. david.amouroux@univ-pau.fr.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Bérail
authors.affiliation: National Institute of Standards and Technology, Hollings Marine Laboratory, Charleston, South Carolina, USA.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Becker
authors.affiliation: Laboratoire Géosciences Environnement Toulouse, Observatoire Midi-Pyrénées CNRS-IRD-Université de Toulouse 3, 14 avenue Edouard Belin, Toulouse, 31400, France.
authors.forename: Jeroen E
authors.initials: JE
authors.lastname: Sonke
authors.affiliation: Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut des Sciences Analytiques et de Physico-chimie pour l'Environnement et les Matériaux, IPREM UMR-5254, CNRS-UPPA, Hélioparc, 2 Avenue du Président Pierre Angot, Pau, 64053, France. david.amouroux@univ-pau.fr.
authors.forename: David
authors.initials: D
authors.lastname: Amouroux
mesh_terms: D000818:Animals; D050643:Beluga Whale / Q000378:metabolism*; D010872:Caniformia / Q000378:metabolism*; D020387:Food Chain; D008401:Gas Chromatography-Mass Spectrometry; D008629:Mercury Isotopes / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D008767:Methylmercury Compounds / Q000032:analysis / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D008629:Mercury Isotopes; D008767:Methylmercury Compounds