Non-technical Project DescriptionEnglishWhy is mercury rising in some northern lakes and not others?Activity lead: Jennifer Galloway, Geological Survey of CanadaSummary of project backgroundIncreases in mercury (Hg) concentrations have been widely reported in lake sediments, peat, surface waters, and fish throughout northern Canada (e.g., the Deh Cho region of the Northwest Territories, the Kivalliq region of Nunavut). Rising Hg is a concern for communities that rely on the land for sustenance and for industry that must follow strict environmental permitting conditions because Hg can be toxic. Anthropogenic emissions of Hg to the atmosphere combined with continued input of Hg from watershed reservoirs (e.g., soil, wetlands) and climate-induced changes (e.g., increased primary production in surface waters, permafrost thaw, changes in fire regime) have increased Hg flux to some environments. This study seeks to understand processes that are affecting Hg concentrations in northern lake sediments. We have conducted analyses on an existing dataset from 60 near-surface lake sediment samples collected from the central Northwest Territories, and we are herein aiming to conduct targeted studies on specific lakes of concern in the Kivalliq region of Nunavut.Justification for the studyThis project seeks to study the behaviour of Hg in lake sediments over hundreds to thousands of years in the Kivalliq region of Nunavut. By using a long-time perspective, we can better understand the cumulative effects of climate change and anthropogenic stressors affecting the accumulation of Hg in lakes. By determining the factors that have caused increases in Hg concentration in lake sediments, people can be better positioned to mitigate exposure and make informed land use decisions. Where, when, and how long the field research will take placeWe seek to sample the sediment from 4 lakes in the Kivalliq region of Nunavut. The lakes have been identified in consultation with the community of Rankin Inlet (HTO) and the Kivalliq Inuit Association. The timing of the field research has been determined through consultation with community members of Rankin Inlet and the KIA. It will take place during 7-10 days in August 2026 from a helicopter equipped with floats.We would like to employ 1 or 2 wildlife monitor(s) at the daily rate set by the Kangiqliniq HTO for approx. 7-10 days. We would also like to hire a local interpreter, based on fair rates for their time and expertise. We will seek to rent a local venue space for use in public consultation and results-sharing sessions when results are ready. MethodsSampling of the lake-bed will occur using a gravity corer. The gravity corer is a 5 to 10 cm diameter wide by 0.5 to 1 m long open-tubed core that is lowered into the sediment. When drawn up, the corer takes the intercepted lake sediments with it (like a straw). We may also employ a freeze corer, which is a metal triangular tube about 30 cm in diameter in total and up to 1 m long. It freezes about 3 cm thick of sediment onto the surface of 1 or 2 metal faces.The retrieved lake sediments are then sub-sampled on site (gravity corer) or in a lab (freeze corer). The resulting lake sediment sub-samples are then sent to laboratories for various analyses, including determination of the age of the sediment, concentration of Hg and other elements, determination of the type of organic matter, and sediment grain size. How, when, and with whom research results will be shared in NunavutThe communication strategy will be developed with community members of Rankin Inlet and will occur throughout 2025 and 2026 (when our funding will end) by means of community visits and community-based workshops. We will try our best to address any other knowledge transfer activities requested by community members. Data produced by this project will be numerical and will be reposited in the POLAR Data Catalogue, an online and open -source database hosted by the Government of Canada (Polar Data Catalogue).