Chemistry and deposition of mineral aerosol over Southern oceanic area

• Main Author: Heimburger, Alexie
• Other Authors: Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA (UMR_7583)), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Diderot - Paris VII, Rémi Losno([e-mail]), Projet FLATOCOA financé par l'IPEV
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2013
• Subjects: Atmospheric deposition; Southern Ocean; atmosphere-ocean interactions; trace metalsn solubility; uncertainties; Dépôt atmosphérique; océan austral; interaction océan-atmosphère; métaux traces; solubilité; traceurs de sources; incertitudes; HR-ICP-MS; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Austral; Îles Kerguelen; Indian; Kerguelen; Kerguelen Islands; Crozet Islands
• Online Access: https://tel.archives-ouvertes.fr/tel-00849747; https://tel.archives-ouvertes.fr/tel-00849747/document; https://tel.archives-ouvertes.fr/tel-00849747/file/Memoire_these_Alexie_Heimburger.pdf

Atmospheric supplies bringing trace metals are believed to have a significant impact on biogeochemical processes in HNLC oceanic areas. Time series of atmospheric deposition samples and aerosols were continuously collected in 2009-2010 on Kerguelen and Crozet Islands in the Southern Indian Ocean. We found very low levels of dust concentrations and high total dust deposition fluxes, which are in good agreement with atmospheric models but not with previous observations. Scavenging ratio calculation highlights that surface concentrations are not representative of the total dust column. This leads to the conclusion that deposition flux is difficult to derive from aerosol surface concentrations at remote ocean sites. Deposition fluxes were also presented for a suite of elements identified as coming either from sea-salt and crustal sources. Some of them (Pb, As, .) have an anthropogenic contribution during the winter only. Al, Fe, Mn and Si deposition fluxes are similar for the both locations; we observed differences for the other non-sea-salt elements from a factor of two to a factor of five with a decreasing gradient from Crozet to Kerguelen Islands. Pb isotopic ratios highlight that aerosols on Kerguelen Islands come predominantly from South America; Crozet Island receives aerosols from South Africa. REE profiles could confirm this behavior. Finally, concentrations in rainwaters are very low and difficult to measure accurately because of possible contamination issues. Deduced solubilities are generally high. Les apports atmosphériques sont suspectés de jouer un rôle important dans les processus biogéochimiques des régions océaniques HNLC. Des échantillons de dépôt atmosphérique total et d'aérosols ont été collectés en continu entre 2009 et 2010 dans l'océan austral indien, aux îles Kerguelen et de Crozet. Ils ont été mesurés par HR-ICP-MS. Les concentrations en surface des aérosols terrigènes sont basses et ne peuvent rendre compte des flux de dépôt de poussières qui sont plus élevés que ceux précédemment ...