Role of the Hyporheic Zone in Methylmercury Production and Transport to Lake Superior

This investigation will focus on the role of the hyporheic zone in the production and transport of methyl mercury to Lake Superior. The objectives are: (1) To measure methyl mercury levels and rates of mercury methylation and demethylation in contrasting hyporheic zones in the Lake Superior Watershed, and (2) to evaluate the potential flux of methyl mercury to Lake Superior from these zones through measurements of hydraulic conductivities and gradients. We will make comparative measurements near the river mouth in the Tahquamenon and Salmon Trout Rivers to compare the influences of wetland and forested watersheds. Measurements of methylation and demethylation rates, mercury and methyl mercury concentrations, and water levels in hyporheic zone waters. Measurements will be made seasonally during three sampling trips per year over the two year project period.