Quantifying wet and dry atmospheric inputs of mercury to Manitoba Hydro reservoirs and watersheds

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Hydroelectricity is currently touted as relatively "green" due to its low per unit energy greenhouse gas emissions. However, reservoir creation has many other environmental impacts, including the production and bioaccumulation of methylmercury (MeHg; a toxic form of Hg) into fish. To accurately quantify the net effect of reservoir creation on the biogeochemical cycling of Hg, researchers require measures of atmospheric loadings of Hg to intact forested watersheds, and an understanding of how these inputs change following flooding. These atmospheric inputs of MeHg and inorganic Hg(II) can then be subtracted from exports of MeHg and Hg(II) from reservoirs to determine, for example, the net production of MeHg within the reservoir itself. The overall objective of our proposal is to quantify wet and dry atmospheric inputs of MeHg and Hg(II) to Manitoba Hydro reservoirs and watersheds. This will be accomplished by initiating a wet deposition Hg monitoring program at a Manitoba Hydro generating station to be used in conjunction with a long-term and expanding dataset of wet and dry deposition being collected at the Experimental Lakes Area in northwestern Ontario. Our research will allow Manitoba Hydro to more accurately quantify and predicatively model the net impact of reservoir creation on the biogeochemical cycling of Hg and the bioaccumulation of MeHg in fish. Such information will also allow Manitoba Hydro to accurately compare its net Hg "footprint" per unit energy produced relative to that associated with burning coal in North America to produce an equivalent amount of electricity, and better explain the environmental benefits of hydroelectricity production. Our dataset will also contribute to ongoing studies examining the net export of Hg from Manitoba Hydro watersheds to Hudson Bay, where certain species of marine mammals contain high enough concentrations of Hg to be of concern to First Nations peoples using them as a traditional food source. Finally, our proposed research will contribute via the newly initiated Environment Canada Clean Air Regulatory Agenda (CARA) Mercury Science Program to our overall understanding of Hg deposition across Canada.