J. Phys. IV France 107 (2003) 509
DOI: 10.1051/jp4:20030352

Dissolve gaseous mercury distribution in a wetland: Influence of macrophyte beds

E. Garcia¹, J. Laroulandie¹, M. Amyot² and X.R. Saint-Simon<sup>1

1</sup>  Institut National de la Recherche Scientifique (INRS), Eau, Terre et Environnement, Université du Québec, 2800 rue Einstein, CP. 7500, Sainte-Foy, Québec G1 V 4C7, Canada
²  Département des Sciences Biologiques, D223, Pavillon Marie-Victorin, Université de Montréal, 90 Vincent d'Indy, Montréal H2V 2S9, Canada

Abstract
In wetlands, the presence of macrophytes and associated organisms may alter the redox chemistry of Hg, affecting the cycling of atmospheric Hg species at the airlwater interface. As part of a contribution to the Collaborative Mercury Research Network (COMERN), we investigated the spatial distribution of dissolved gaseous mercury (DGM) in subsurface waters from the Baie St. François wetland, in the St Lawrence River. DGM concentrations varied in different macrophyte beds and in macrophyte-free areas, ranging from 48.6 to 75.3 pg.L ^-1 (1388-2151% saturation relative to atmospheric equilibrium). The highest DGM concentration was observed in the bed of Elodea canadensis, a submerged plant, and the lowest, in open areas. Our results indicated that macrophyte beds may constttute a significant site for Hg reduction. Macrophytes may also interfere with the evasion of Hg to the atmosphère, by providing a shelter against wind and waves.

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