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

Year: 2016

Authors: Angot H., Magand O., Helmig D., Ricaud P., Quennehen B., Gallée H., Del Guasta M., Sprovieri F., Pirrone N., Savarino J., Dommergue A.

Autors Affiliation: Univ Grenoble Alpes, LGGE, F-38041 Grenoble, France; CNRS, LGGE, F-38041 Grenoble, France; Univ Colorado, Inst Arctic & Alpine Res INSTAAR, Boulder, CO 80309 USA; CNRS, Meteo France, GAME, CNRM, 42 Ave Coriolis, F-31057 Toulouse, France; CNR, Ist Nazl Ott, Largo E Fermi 6, I-50125 Florence, Italy; CNR, Inst Atmospher Pollut Res, Div Rende, Arcavacata Di Rende, Italy; CNR, Inst Atmospher Pollut Res, Rome, Italy.

Abstract: 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 degrees 06’S. 123 degrees 20’E, 3220m 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.

Journal/Review: ATMOSPHERIC CHEMISTRY AND PHYSICS

Volume: 16 (13)      Pages from: 8249  to: 8264

More Information: We thank A. Barbero and the rest of the overwintering crew: S. Aubin, C. Lenormant, and R. Jacob. We also gratefully acknowledge M. Barret for the development of a QA/QC software program, L. Bonato for the analysis of total mercury in surface snow samples, D. Liptzin for the calculation of the Obukhov length and friction velocity, M. Legrand for the 2012 ozone data, C. Genthon for the meteorological data, E. Vignon for helpful discussion, and B. Jourdain and X. Fain for their help in the field. This work contributed to the EU-FP7 project Global Mercury Observation System (GMOS – www.gmos.eu) and has been supported by a grant from Labex OSUG@2020 (Investissements d
KeyWords: atmospheric chemistry; chemical cycle; concentration (composition); dry deposition; mercury (element); monitoring; photochemistry; reaction kinetics, Antarctic Plateau; Antarctica; Concordia Station; East Antarctica
DOI: 10.5194/acp-16-8249-2016

Citations: 32
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