Hydrogeochemical dynamics of a potential talik aquifer beneath the Kuuguluk River, Salluit, Nunavik (Québec, Canada)

Abstract Guaranteeing year-round access to safe, sustainable drinking water is a major challenge for many northern communities in Canada. This study offers the first hydrochemical and isotopic analysis of the Kuuguluk River and its river talik, in Salluit, Nunavik (Québec, Canada), based on water samples collected during a field campaign in October 2024. Major ion analyses showed a predominantly Ca–HCO 3 composition, with generally low mineral saturation indices in surface and shallow groundwater, suggesting, in conjunction with high tritium levels, recent meteoric recharge with minimal geochemical evolution. Deeper groundwater showed higher solute concentrations, enhanced sediment–water interactions, and slightly lower tritium levels, consistent with recent recharge, but longer residence time. Although tritium concentrations support the dominance of modern recharge, radiocarbon-depleted signatures of dissolved inorganic and organic carbon, particularly in deeper groundwater, suggest interaction with aged organic matter, potentially from degrading permafrost. Dissolved radon measurements qualitatively suggest increased downstream groundwater contributions, supporting numerical model predictions regarding hydraulic connectivity between the river talik and the river in this continuous permafrost environment. The findings emphasize the significance of groundwater in river talik as a potentially perennial drinking water resource in this area, an important finding that may be applicable to other continuous permafrost environments. Ongoing multidisciplinary monitoring (hydraulic head and temperature) and future modelling will be essential for ensuring the long-term viability of the Kuuguluk River talik aquifer as a potential municipal drinking water source for the community of Salluit.