Fluxes of Mercury and Methylmercury in Permafrost Thaw Lakes

December 16, 2026

The evolving Arctic environment, characterized by gradual permafrost degradation, has promoted the remobilization of previously stored mercury (Hg) (and other chemical and biological constituents), impacting its biogeochemical cycle. Thermokarst lakes, formed through the thawing of ice-rich permafrost, are recognized hotspots for Hg mobilization and methylation (i.e., conversion to monomethylmercury, MMHg, the most neurotoxic Hg form). This study investigates the magnitude and underlying mechanisms driving mercury mobilization at the sediment/water interface (SWI) in a thermokarst lake (Lake SAS-1A) and compares them to those observed in a nearby reference bedrock lake (Lake K9), the latter being non-impacted by permafrost degradation. Both lakes are located in the Whapmagoostui–Kuujjuarapik territory of Nunavik, a sporadic permafrost region of the Canadian Sub-Arctic. The field campaign was conducted during the frost-free season (summer), during which a benthic flux chamber (BFC) was used to collect bottom water samples from each lake. The objective was to monitor the temporal evolution of mercury (and other chemical constituents) concentration and, ultimately, to assess and investigate the fluxes at the sediment/water interface. Mercury fluxes in both Lake SAS-1A and Lake K9 revealed to be negative, and of similar magnitude (-65,4 ± 34,6 ng h-1m-2 and -66,5 ± 42,5 ng h-1m-2, respectively), suggesting that Hg (particularly Hg2+) delivery to the sediment/water interface (SWI) through particulate processes occurring in the water phase dominated over upward diffusion from sediments.

Authors in the community:

• 

  S

  Silvia Alina Buriac

  ist196670

Supervisors of this institution:

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  R

  Rute Isabel Talhadas Cesário

  ist171221

• 

  J

  João Alfredo Vieira Canário

  ist90799

chemical-engineering - Chemical engineering

por - Portuguese

Instituto Superior Técnico