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Methyl mercury dynamics in littoral sediments of a temperate seepage lake

January 1, 1998

The sites and rates of methyl mercury (MeHg) production and transport in littoral zone sediments were investigated at Pallette Lake in northern Wisconsin. In littoral areas where groundwater inflow occurs, sulfate supply from groundwater creates profiles of electron acceptors (sulfate) and donors (methane, sulfide) that are reversed from those found in sediments whose sulfate supply is delivered from overlying water. The highest MeHg concentrations in porewaters and the maximal advective MeHg flux rates (4.5-61.7 ng ·m-2 ·day-1) were observed in the spring, while highest bulk phase concentrations occur later in the summer. These estimated MeHg fluxes are greater than the mean areal production rates estimated previously for the water column and are similar to the atmospheric flux. Gross MeHg production was measured using the addition of 203Hg as a tracer to sediments. The depth at which maximal 203Hg methylation occurred coincided with the observed maximums in solid-phase and porewater MeHg concentrations. Because input, advection, and accumulation of MeHg in these sediments were measured directly, an independent estimate of MeHg production could be made and compared with 203Hg-derived rates. This comparison suggests that that the 203Hg tracer method provides reasonable estimates of gross methylation rates and that a substantial fraction of solid-phase Hg is available for methylation

Citation Information

Publication Year 1998
Title Methyl mercury dynamics in littoral sediments of a temperate seepage lake
DOI 10.1139/f97-304
Authors D. P. Krabbenhoft, C.C. Gilmour, J.M. Benoit, Christopher L. Babiarz, A.W. Andren, J.P. Hurley
Publication Type Article
Publication Subtype Journal Article
Series Title Canadian Journal of Fisheries and Aquatic Sciences
Index ID 70020870
Record Source USGS Publications Warehouse
USGS Organization Toxic Substances Hydrology Program