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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 21 | Copyright
Atmos. Chem. Phys., 18, 15825-15840, 2018
https://doi.org/10.5194/acp-18-15825-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 05 Nov 2018

Research article | 05 Nov 2018

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

Shaojie Song1,a, Hélène Angot2, Noelle E. Selin1,2, Hubert Gallée3, Francesca Sprovieri4, Nicola Pirrone5, Detlev Helmig6, Joël Savarino3, Olivier Magand3, and Aurélien Dommergue3 Shaojie Song et al.
  • 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
  • 2Institute for Data, Systems and Society, Massachusetts Institute of Technology, Cambridge, MA, USA
  • 3Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, Institut des Géosciences de l'Environnement (IGE), Grenoble, France
  • 4CNR-Institute of Atmospheric Pollution Research, Rende, Italy
  • 5CNR-Institute of Atmospheric Pollution Research, Montelibretti, Rome, Italy
  • 6Institute of Arctic and Alpine Research (INSTAAR), University of Colorado, Boulder, CO, USA
  • anow at: School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA

Abstract. Distinct diurnal and seasonal variations of mercury (Hg) have been observed in near-surface air at Concordia 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 Hg0 (gaseous elemental mercury) measurements in thes year 2013. The model includes atmospheric Hg0 oxidation (by OH, O3, or bromine), surface snow HgII (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 Hg0 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 Hg0 (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 Hg0 is mainly driven by photoreduction of snow HgII in summer. Intermittent warming events and a hypothesized reduction of HgII 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 Hg0 is expected to be slower at Summit Station in Greenland than at Concordia (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 Hg0 between these two polar inland stations.

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Mercury is a trace metal with adverse health effects on human and wildlife. Its unique property makes it undergo long-range transport, and even remote Antarctica receives significant inputs. This paper presents the first model that aims to understand mercury behavior over the Antarctic Plateau. We find that mercury is quickly cycled between snow and air in the sunlit period, likely driven by bromine chemistry, and that several uncertain processes contribute to its behavior in the dark period.
Mercury is a trace metal with adverse health effects on human and wildlife. Its unique property...
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