New insights into the atmospheric mercury cycling in central Antarctica and implications on a continental scale

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Angot, Hélène, Magand, Olivier, Helmig, Detlev, Ricaud, Philippe, Quennehen, Boris, Gallée, Hubert, Del Guasta, Massimo, Sprovieri, Francesca, Pirrone, Nicola, Savarino, Joël, Dommergue, Aurélien
• Other Authors: Laboratoire de glaciologie et géophysique de l'environnement (LGGE), Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 )-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 )-Centre National de la Recherche Scientifique (CNRS), Institute of Arctic and Alpine Research (INSTAAR), University of Colorado Boulder, Groupe d'étude de l'atmosphère météorologique (CNRM-GAME), Institut national des sciences de l'Univers (INSU - CNRS)-Météo France-Centre National de la Recherche Scientifique (CNRS), Istituto Nazionale di Ottica (INO), Consiglio Nazionale delle Ricerche (CNR), Institute of Atmospheric Pollution Research (IIA), Consiglio Nazionale delle Ricerche Roma (CNR)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2016
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; Antarctic; The Antarctic; East Antarctic Ice Sheet; Concordia Station; Antarc*; Antarctica; Ice Sheet
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-01391379; https://hal-insu.archives-ouvertes.fr/insu-01391379/document; https://hal-insu.archives-ouvertes.fr/insu-01391379/file/ATMOSPHERIC%20CHEMISTRY%20AND%20PHYSICS%20-%20New%20insights%20into%20the%20atmospheric%20mercury%20cycling%20in%20central%20Antarctica%20and%20implications%20on%20a%20continen.pdf; https://doi.org/10.5194/acp-16-8249-2016

International audience Under the framework of the GMOS project (Global Mercury Observation System) atmospheric mercury monitoring has been implemented at Concordia Station on the high-altitude Antarctic plateau (75 • 06 S, 123 • 20 E, 3220 m above sea level). We report here the first year-round measurements of gaseous elemental mercury (Hg(0)) in the atmosphere and in snowpack interstitial air on the East Antarctic ice sheet. This unique data set shows evidence of an intense oxidation of atmospheric Hg(0) in summer (24-hour daylight) due to the high oxidative capacity of the Antarctic plateau atmosphere in this period of the year. Summertime Hg(0) concentrations exhibited a pronounced daily cycle in ambient air with maximal concentrations around midday. Photochemical reactions and chemical exchange at the air–snow interface were prominent, highlighting the role of the snowpack on the atmospheric mercury cycle. Our observations reveal a 20 to 30 % decrease of atmospheric Hg(0) concentrations from May to mid-August (winter, 24 h darkness). This phenomenon has not been reported elsewhere and possibly results from the dry deposition of Hg(0) onto the snowpack. We also reveal the occurrence of multi-day to weeklong atmospheric Hg(0) depletion events in summer, not associated with depletions of ozone, and likely due to a stagnation of air masses above the plateau triggering an accumulation of oxidants within the shallow boundary layer. Our observations suggest that the inland atmospheric reservoir is depleted in Hg(0) in summer. Due to katabatic winds flowing out from the Antarctic plateau down the steep vertical drops along the coast and according to observations at coastal Antarctic stations, the striking reactivity observed on the plateau most likely influences the cycle of atmospheric mercury on a continental scale.