Department of geography
Pascale Roy-Léveillée (Regular member)
Introduction: The rapid degradation of cryogenic mounds, caused by climate change, results in the release of a significant amount of mercury (Hg) that was previously sequestered in permafrost into the environment. Under favourable conditions, Hg can be converted via methylation, a microbial process, to methylmercury (CH3Hg or MeHg), a neurotoxic form of Hg that can bioaccumulate in animals and humans and can be biomagnified along the food chain. This research aims to determine if the geomorphological evolution of degrading cryogenic mounds near Kangiqsualujjuaq, Nunavik (QC), creates environments conducive to the mobilization of Hg into adjacent waterways and its subsequent methylation. Objectives: Three specific objectives were identified to address this question: Characterize the recent geomorphic evolution of a cryogenic mound field located on a stream floodplain; Evaluate the vertical distribution of soil Hg in different components of the selected degrading mound field and its floodplain; Determine if mound degradation promotes mobilization of Hg to environments that favour its methylation. Study sites: Kangiqsualujjuaq, also known as George River, is located on the east coast of Ungava Bay (58°69′ N; 65°97′ W) and is one of the 14 Inuit communities of Nunavik. This subarctic village is located at the tree line and in a zone of discontinuous and widespread permafrost. In this area, cryogenic mounds, formed by the uplift of the ground surface during the aggradation of segregated ice in glaciomarine sediments, show signs of degradation, including along water bodies where the community traditionally fishes. Material and methods: The evolution of cryogenic mounds and associated water bodies over the past 50 years will be mapped using a combination of aerial photographs, satellite images, and in situ observations. In the field, samples from various components of the mound field (e.g., mound, residual bulge, thermokarst pool, riverbed) will be methodically collected along the mound degradation toposequence using a portable drill system, then analyzed in the laboratory for total Hg (THg). Finally, the soil samples, as well as stream water and sediment samples collected upstream and downstream from the study area, will be analyzed for MeHg. Expected results: Thus far, there are no known studies that use a primarily geomorphic approach to investigate Hg sequestration in permafrost. This multidisciplinary study, which combines permafrost geomorphology and Hg biogeochemistry, will contribute to the fundamental knowledge of Hg mobilization in degrading mound fields and will improve the understanding of the local environmental configuration of a degrading mound site in Kangiqsualujjuaq. The results will also help to better target the monitoring of contaminants in water and animals, which is essential to the food security of northern communities.
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