Application of enriched stable mercury isotopes to the Lake 658 watershed for the METAALICUS Project, at the experimental lakes area, northwestern Ontario, Canada

A whole-ecosystem experiment was conducted at the Experimental Lakes Area (ELA) in northwestern Ontario in an effort to study the relationship between atmospheric deposition of mercury and mercury accumulation in fish, as well as the biogeochemical processing of mercury within watersheds. The mercury experiment to assess atmospheric loading in Canada and the United States (METAALICUS) also examined the relative importance of newly deposited mercury onto wetlands, uplands and the lake surfaces as sources of mercury to fish and other biota. It examined how quickly mercury concentrations in the lake, upland and wetland respond to changes in mercury deposition rate, and the relative importance of newly deposited mercury as compared to mercury present in the ecosystem from previous years. Atmospheric loadings of mercury to the watershed were increased to 4 times the rate normally found in wet deposition in the region using enriched stable isotopes of mercury. This report presented a site description of Lake 658 in the ELA and outlined the preparation of enriched stable mercury isotope solutions as well as the methods for applying mercury solutions in lakes and wetlands. By the end of the experiment, the accumulated loadings to the watershed areas were quite similar, with the upland areas receiving slightly less than the lake, per unit area, and the wetland area receiving slightly more. The total mercury loadings to the upland, wetland and lake from 2001 to 2003 were 62,78 and 66 μg per m2 respectively. 11 refs., 33 tabs., 18 figs