The chemistry and transport of mercury in a small wetland in the Adirondack region of New York, USA

The biogeochemistry of Hg was evaluated in a small wetland in the Adirondack region of New York. Concentrations of total Hg (Hg(T)) in streamwater draining the wetland showed little temporal variation. The annual areal watershed flux of Hg(T) (2.2 μg/m²-yr) was considerably smaller than regional inputs of atmospheric deposition of Hg(T), indicating that the terrestrial environment is a net sink for atmospheric deposition of Hg(T). Drainage inputs of Hg(T) were conservatively transported through the beaver impoundment. The annual flux of total methylmercury (CH₃Hg(T)⁺) was greater than literature values of atmospheric deposition suggesting that the watershed is a net source of CH₃Hg(T)⁺. Stream concentrations of CH₃Hg(T)⁺ increased during low-flow summer conditions in a riparian wetland, and particularly at the outlet of the beaver impoundment. Net production of CH₃Hg(T)⁺ occurred in the beaver impoundment (0.45 μg/m²-yr). Rates of net methylation for the beaver impoundment were comparable to values reported in the literature for wetlands.