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 methyl mercury (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.