Understanding mercury oxidation and air–snow exchange on the East Antarctic Plateau: a modeling study

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Song, Shaojie, Angot, Hélène, Selin, Noelle, Gallée, Hubert, Sprovieri, Francesca, Pirrone, Nicola, Helmig, Detlev, savarino, Joel, Magand, Olivier, Dommergue, Aurélien
• Other Authors: Massachusetts Institute of Technology (MIT), Institut des Géosciences de l’Environnement (IGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Institute of Atmospheric Pollution Research (IIA), Consiglio Nazionale delle Ricerche Roma (CNR), Institute of Arctic and Alpine Research (INSTAAR), University of Colorado Boulder, Université Grenoble Alpes 2016-2019 (UGA 2016-2019 ), Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Antarctic; Austral; Greenland; Antarc*
• Online Access: https://hal.archives-ouvertes.fr/hal-02350377; https://hal.archives-ouvertes.fr/hal-02350377/document; https://hal.archives-ouvertes.fr/hal-02350377/file/acp-18-15825-2018.pdf; https://doi.org/10.5194/acp-18-15825-2018

International audience Distinct diurnal and seasonal variations of mercury (Hg) have been observed in near-surface air at Con-cordia Station on the East Antarctic Plateau, but the processes controlling these characteristics are not well understood. Here, we use a box model to interpret the Hg 0 (gaseous elemental mercury) measurements in thes year 2013. The model includes atmospheric Hg 0 oxidation (by OH, O 3 , or bromine), surface snow Hg II (oxidized mercury) reduction, and air-snow exchange, and is driven by meteorological fields from a regional climate model. The simulations suggest that a photochemically driven mercury diurnal cycle occurs at the air-snow interface in austral summer. The fast oxidation of Hg 0 in summer may be provided by a two-step bromine-initiated scheme, which is favored by low temperature and high nitrogen oxides at Concordia. The summertime diurnal variations of Hg 0 (peaking during daytime) may be confined within several tens of meters above the snow surface and affected by changing mixed layer depths. Snow re-emission of Hg 0 is mainly driven by photoreduction of snow Hg II in summer. Intermittent warming events and a hypothesized reduction of Hg II occurring in snow in the dark may be important processes controlling the mercury variations in the non-summer period, although their relative importance is uncertain. The Br-initiated oxidation of Hg 0 is expected to be slower at Summit Station in Greenland than at Con-cordia (due to their difference in temperature and levels of nitrogen oxides and ozone), which may contribute to the observed differences in the summertime diurnal variations of Hg 0 between these two polar inland stations.