Sulfide and mercury species profiles in two Ontario boreal shield lakes.

The cycling of sulfur in freshwater environments plays an important role in the cycling of metals. In this study, acid volatile sulfides were measured at nanomolar levels using a purge-and-trap preconcentration, followed by methylene blue derivatization with HPLC separation and UV-Vis detection. The limit of detection using the preconcentration step was 7.5ngL(-1) or 0.23nM sulfide. Profiles of sulfide and methylmercury were generated for two Ontario lakes. Sulfide concentrations were inversely related to dissolved oxygen concentrations and significant levels of anoxia had developed in both lakes. In both Plastic Lake and Lake 658, mercury concentrations also increased below the oxycline. Lake 658 showed a strong positive correlation between sulfide and methylmercury (CMeHg=2×10(-6)⋅Csulfide+0.198; r=0.96, p=1.2×10(-5)), at the time of sampling.