Mercury Export Flux in the Arctic Ocean Estimated from 234 Th/ 238 U Disequilibria

• Published in: ACS Earth and Space Chemistry
• Main Authors: Tesán Onrubia, Javier, Petrova, Mariia, Puigcorbé, Viena, Black, Erin, Valk, Ole, Dufour, Aurélie, Hamelin, Bruno, Buesseler, Ken, Masqué, Pere, Le Moigne, Frédéric A.C., Sonke, Jeroen, Rutgers van Der Loeff, Michiel, Heimbürger-Boavida, Lars-Eric
• Other Authors: Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Partenaires INRAE, Dalhousie University Halifax, Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Woods Hole Oceanographic Institution (WHOI), School of Natural Sciences and Centre for Marine Ecosystems Research, Edith Cowan University, EDITH COWAN UNIVERSITY-EDITH COWAN UNIVERSITY, Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: GEOTRACES; particulate mercury; Arctic Ocean; thorium export; particle export flux; [SDU]Sciences of the Universe [physics]; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Arctic
• Online Access: https://hal.science/hal-02935259; https://hal.science/hal-02935259/document; https://hal.science/hal-02935259/file/Final_version_exported_from_the_PhD.pdf; https://doi.org/10.1021/acsearthspacechem.0c00055

International audience High mercury (Hg) levels have been observed for arctic biota despite limited localsources of anthropogenic Hg in the Arctic. Scavenging of Hg exerts an important control onthe residence time of Hg in surface waters. The downward Hg export flux, as well as Hgburial rates in bottom sediments, are not well constrained due to the lack of particulate Hg(pHg) observations in the Arctic Ocean. Here we estimated downward Hg export flux basedon Hg concentrations in suspended particulate matter (SPM) and by using the radionuclidepair 234Th/238U, coupled to pHg/234Th ratios in particles. Using new observations made duringthe German GEOTRACES TransArcII (GN04) and the U.S. Arctic GEOTRACES (GN01)cruises in August - October 2015, we estimated the pHg export flux in the central ArcticOcean and the outer shelf. We find that 81 ± 58 Mg y-1 pHg are exported from the upper 100m, of which 16 ± 10 Mg y-1 are ultimately buried in marine sediments. An extrapolation tothe entire Arctic Ocean, including the inner shelf, results in 156 Mg y-1 pHg export from thesurface ocean and 28 Mg y-1 Hg burial rate. Our study shows that the pHg export flux couldbe higher than previously thought and this should be taken into consideration for future arcticHg budget estimations.