Are methylmercury concentrations in the wetlands of Kejimkujik National Park, Nova Scotia, Canada, dependent on geology?

In the relatively pristine ecosystem in Kejimkujik Park, Nova Scotia, methylmercury (MeHg) concentrations in loons, Gavia immer, are among the highest recorded anywhere in the world. This study investigated the influence of bedrock lithology on MeHg concentrations in wetlands. Twenty-five different wetland field sites were sampled over four different bedrock lithologies; Kejimkujik monzogranite, black sulfidic slate, gray slate, and greywacke. Soil samples were analyzed for ethylmercury (EtHg), MeHg, total Hg, acid-volatile sulfides (AVS), organic matter, and water content as well as the biological parameters, mercury methyltransferase (HgMT) activity, sulfate reduction rates, fatty acid methyl ester (FAME) composition, and acidity. Methylmercury concentrations in the wetlands were highly dependent (P < 0.08) on lithology with no significant difference between bogs, fens, and swamps. Methylmercury concentrations in wetland soils developed on Kejimkujik monzogranite averaged 900 ng kg(-1) compared with only 300 ng kg(-1) in wetland soils developed on black sulfidic slate. Fatty acid methyl ester composition was also lithologically dependent (P < 0.001) with biomarkers for Desulfobulbus spp. discriminating between sites containing high and low MeHg concentrations. Levels of MeHg in wetlands were predicted mainly (41% of the sum of squares) by HgMT activity that differed (P < 0.009) between wetlands, with activity in bogs almost three times that present in swamps. Wetland MeHg concentrations are highly dependent on the lithology on which they have developed for largely biological reasons.

Hg(II) adsorption by bacteria: a surface complexation model and its application to shallow acidic lakes and wetlands in Kejimkujik National Park, Nova Scotia, Canada.

The fate and environmental threat posed by mercury in aquatic systems is controlled, in part, bythe transport of Hg(II) from oxic to anoxic zones in lakes and its subsequent transformation to organic mercury. The transport of Hg(II) in aquatic systems can be affected by its partitioning between the dissolved and particulate phases. In this study, batch experiments were performed to quantify Hg(II) adsorption to Bacillus subtilis as bacteria-to-metal ratio, pH, chloride concentration, growth phase, and reaction time were independently varied. The laboratory data were well described by a surface complexation model (SCM) considering the adsorption of neutral Hg(II) hydroxide and chloride complexes by specific functional groups on the bacterial surface. To evaluate its applicability to complex aquatic systems, the SCM was used to predict the distributions of Hg(II) in 36 shallow acidic lakes and wetlands in Kejimkujik National Park, Nova Scotia, Canada. The lab-derived SCM provided a statistically accurate (r2 = 0.615, P < 0.01) fit to the field data when it was expanded to consider Hg(II) complexation by dissolved organic matter. Inclusion of Hg(II)-mineral adsorption reactions did not improve the fit of the model. The quality of fit provided by the expanded SCM suggested that the major assumptions implicit in applying a lab-derived model to the field were justifiable. Our study has demonstrated that SCMs are powerful tools for dynamic prediction of the sorption of environmental contaminants to biocolloids at the regional scale.