Contrasted release of insoluble elements (Fe, Al, REE, Th, Pa) after dust deposition in seawater: a tank experiment approach

Type Article
Acceptance Date 2020 IN PRESS
Language English
Author(s) Roy-Barman Matthieu1, Folio Lorna1, Douville Eric1, Leblond Nathalie2, Gazeau Frédéric3, Bressac Matthieu3, 4, Wagener Thibaut5, Ridame Céline6, Desboeufs Karine7, Guieu Cécile3
Affiliation(s) 1 : Université Paris-Saclay, CNRS, CEA, UVSQ, Laboratoire des Sciences du Climat et de l'Environnement, 91191, Gif-sur-Yvette, France
2 : Sorbonne Université, CNRS, Institut de la Mer de Villefranche, IMEV, F-06230 Villefranche-sur-Mer, France
3 : Sorbonne Université, CNRS, Laboratoire d'Océanographie de Villefranche, LOV, F-06230 Villefranche-sur-Mer, France
4 : Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia
5 : Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
6 : Sorbonne Université, LOCEAN, 4 Place Jussieu – 75252 Paris Cedex 05, France
7 : LISA, UMR7583, Université de Paris, Université Paris-Est-Créteil, Institut Pierre Simon Laplace (IPSL), Créteil, France
Source Biogeosciences (1726-4189) (Copernicus GmbH) In Press
DOI 10.5194/bg-2020-247
Note Special issue | Atmospheric deposition in the low-nutrient-low-chlorophyll (LNLC) ocean: effects on marine life today and in the future (BG/ACP inter-journal SI)(BG/ACP inter-journal SI) Editor(s): Christine Klaas, Cecile Guieu, Karine Desboeufs, Jan-Berend Stuut, Mark Moore, Paraskevi Pitta, Silvia Becagli, and Chiara Santinelli
Abstract

The release of lithogenic elements (which are often assumed to be insoluble) such as Aluminum (Al), Iron (Fe), Rare Earth Elements (REE), Thorium (Th) and Protactinium (Pa) by Saharan dust reaching Mediterranean seawater was studied through tank experiments over 3 to 4 days under controlled conditions including control without dust addition and dust seeding under present and future climate conditions (+3 °C and −0.3 pH unit). Unfiltered surface seawater from 3 oligotrophic regions (Tyrrhenian Sea, Ionian Sea and Algerian Basin) were used. The maximum dissolution fractions were low for all seeding experiments: less than 0.3 % for Fe, 1 % for 232Th and Al, about 2–5 % for REE and less than 6 % for Pa. Different behaviors were observed: dissolved Al increased until the end of the experiments, Fe did not dissolve significantly and Th and light REE were scavenged back on the particles after a fast initial release. The constant 230Th/232Th ratio during the scavenging phase suggests that there is little or no further dissolution after the initial Th release. Quite unexpectedly, comparison of present and future conditions indicates that changes in temperature and/or pH influence the release of thorium and REE in seawater, leading to a lower Th release and a higher light REE release under increased greenhouse conditions.

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Roy-Barman Matthieu, Folio Lorna, Douville Eric, Leblond Nathalie, Gazeau Frédéric, Bressac Matthieu, Wagener Thibaut, Ridame Céline, Desboeufs Karine, Guieu Cécile Contrasted release of insoluble elements (Fe, Al, REE, Th, Pa) after dust deposition in seawater: a tank experiment approach. Biogeosciences IN PRESS. Publisher's official version : https://doi.org/10.5194/bg-2020-247 , Open Access version : https://archimer.ifremer.fr/doc/00642/75456/