HR: 0800h
AN: B11B-0406    [Abstracts]
TI: Formation of Methyl Mercury During Restoration of Forested Wetlands in Relation to Hg, S and Fe Geochemistry
AU: * Fredriksson, I
EM: ida.fredriksson@sek.slu.se
AF: Swedish University of Agricultural Sciences, Department of Forest Ecology and Management, Umea, S-90183, Sweden
AU: Skyllberg, U
EM: ulf.skyllberg@sek.slu.se
AF: Swedish University of Agricultural Sciences, Department of Forest Ecology and Management, Umea, S-90183, Sweden
AB: In 1999 the Swedish Parliament adopted fifteen National Environmental Quality Objectives (NEQO), one of these is the objective of "Thriving wetlands" with thee goal to restore 12 000 ha of wetlands until 2010. Given the current knowledge about methyl mercury (MeHg) production in wetlands, and subsequent bioaccumulation, the objective of thriving wetlands may be in conflict with other NEQO. In this project wetland restoration objects in different environmental settings (differing in primary productivity, climate and sulfur and iron geochemistry) are selected. After a pre-treatment period of 1-2 years, wetlands will be restored by increasing the ground water table. Methylation and demethylation rates, determined in incubation experiments using stable isotopes, will be linked to the chemical speciation of Hg, S and Fe in soil and soil solution using techniques like sulfur and iron X-ray absorption near edge spectroscopy (XANES) and Hg extended x-ray absorption fine structure (EXAFS) spectroscopy. This is done both prior to and during the restoration. Because of the strong link between Fe(II) and S(-II) geochemistry we hypothesize that net MeHg production is limited by the availability of dissolved, neutral Hg-sulfides in iron-rich environments. Preliminary data prior to restoration indeed indicate that besides primary productivity, the availability of neutral Hg-sulfides in the pore water of soils is important for the net production of MeHg.
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 0409 Bioavailability: chemical speciation and complexation
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting