Permafrost Thaw Increases Methylmercury Formation in Subarctic Fennoscandia

• Main Authors: Brittany Tarbier (10706886), Gustaf Hugelius (3861676), Anna Britta Kristina Sannel (10706889), Carluvy Baptista-Salazar (10706892), Sofi Jonsson (1694587)
• Format: Other Non-Article Part of Journal/Newspaper
• Language: unknown
• Published: 1753
• Subjects: Biophysics; Cell Biology; Genetics; Molecular Biology; Ecology; Developmental Biology; Environmental Sciences not elsewhere classified; Biological Sciences not elsewhere classified; Chemical Sciences not elsewhere classified; future estimates; 178 soil samples; 14 peat cores; Hg methylation hotspots; thermokarst formation; report HgT; thaw gradients; HgT stocks; carbon ratios representative; peat plateau; food webs; 13 times; Subarctic Fennoscandia Methylmercury; Fennoscandian permafrost peatland sites; collapse fen; Arctic environment; wildlife health; anoxic environments; permafrost soils; MeHg concentrations; 10 times; interquartile range; Total Hg; thermokarst wetlands; Fennoscandian permafrost peatlands; Permafrost Thaw Increases Methylmer.; Arctic; Fennoscandia; Fennoscandian; Peat; Peat plateau; permafrost; Subarctic; Thermokarst
• Online Access: https://doi.org/10.1021/acs.est.0c04108.s001

Methylmercury (MeHg) forms in anoxic environments and can bioaccumulate and biomagnify in aquatic food webs to concentrations of concern for human and wildlife health. Mercury (Hg) pollution in the Arctic environment may worsen as these areas warm and Hg, currently locked in permafrost soils, is remobilized. One of the main concerns is the development of Hg methylation hotspots in the terrestrial environment due to thermokarst formation. The extent to which net methylation of Hg is enhanced upon thaw is, however, largely unknown. Here, we have studied the formation of Hg methylation hotspots using existing thaw gradients at five Fennoscandian permafrost peatland sites. Total Hg (HgT) and MeHg concentrations were analyzed in 178 soil samples from 14 peat cores. We observed 10 times higher concentrations of MeHg and 13 times higher %MeHg in the collapse fen (representing thawed conditions) as compared to the peat plateau (representing frozen conditions). This suggests significantly greater net methylation of Hg when thermokarst wetlands are formed. In addition, we report HgT to soil organic carbon ratios representative of Fennoscandian permafrost peatlands (median and interquartile range of 0.09 ± 0.07 μg HgT g –1 C) that are of value for future estimates of circumpolar HgT stocks.