J. Phys. IV France 107 (2003) 389
DOI: 10.1051/jp4:20030323

Diurnal cycles of interstitial gaseous mercury inside a sub-arctic snow-pack prior to and during snowmelt events

A. Dommergue¹, C.P. Ferrari^{1, 2}, P.-A. Gauchard¹, L. Poissant³ and C.F. Boutron<sup>1, 4

1</sup>  Laboratoire de Glaciologie et Géophysique de l'Environnement du CNRS, 54 rue Molière, BP. 96, 38402 Saint-Martin-d'Hères, France
²  École Polytechnique Universitaire de Grenoble, Université Joseph Fourier, 28 avenue Benoît Frachon, BP. 53, 38041 Grenoble, France
³  Processus Atmosphériques des Toxiques, Service Météorologique du Canada, Environnement Canada-Région du Québec, 105 rue McGill, 7$\rm ^e$ Étage (Youville) Montréal, Québec H2Y 2E7, Canada
⁴  Unités de Formation et de Recherche de Mécanique et de Physique, Université Joseph Fourier, Institut Universitaire de France, BP. 68, 38041 Grenoble, France

Abstract
The snowpack is a medium that greatly interacts with a variety of atmospheric gases. Its role in the mercury depletion events in arctic and sub-arctic regions seems to be crucial though it is poorly understood. We studied an environmental component of mercury that is interstitial gaseous mercury (IGM) present in the air of the snowpack at Kuujjuarapik (55°N, 77°W), Québec in April 2002. Our data demonstrate that the snow-pack plays a major role in the global mercury cycle. Indeed. IGM concentrations exhibit a well-marked diurnal cycle with uninterrupted events of Hg° depletion and production within the snowpack. During snowmelt episode, high IGM concentrations ( -20 ng/cm ³ at a depth of 37 cm) have been recorded. This study gives us the confirmation that Hg° is involved in oxidation processes occurring in the snowpack. Additionally, we assume that the impressive production of Hg° during the daytime may be the results of photoreduction and photo-initiated reduction of Hg(II) complexes.

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