BGC-01 Mercury biogeochemical cycling in the ocean
Distribution of dissolved gaseous mercury concentrations and photo-induced reduction rate constants of divalent mercury in the Southern Beaufort Sea
Sangwoo Eom* , School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea
Hakwon Jeong, School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea
Juhyeong Chae, School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea
Seunghee Han, School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea

Evasion of dissolved gaseous mercury (DGM) constitutes a major sink of mercury (Hg) in the Arctic Ocean. Although distributions of DGM concentrations in relation to seawater properties in the Arctic Ocean have been reported in a few studies, those of photoreduction rate constant (kr) of Hg(II) have not been investigated; thus, there are limitations in the prediction of the potential changes in the DGM concentration and evasion rate induced by climate change. To understand the link between seawater properties and DGM production rate (and concentrations) in the Arctic Ocean, the DGM concentration and kr of seawater, which is greatly affected by Mackenzie River plume and permafrost thawing, were measured in the Southern Beaufort Sea. Seawater samples were collected using a rosette sampling system equipped with acid-cleaned 10 L Niskin bottles from 15 stations in August and September 2022 on R/V Araon. The kr values and continuous DGM concentrations were immediately measured on board during the cruise. The concentrations of total Hg, dissolved organic carbon and inorganic nutrients, and other ancillary parameters, including excitation emission matrix (EEM) fluorescence and inorganic nutrient concentrations, were later measured in the Trace Metal Biogeochemistry Laboratory at the Gwangju Institute of Science and Technology (GIST). DGM in surface seawater ranged from 0.10 to 0.63 pM, and it was highest in the seater adjacent to the coastal shelf and central Arctic Ocean. Vertically, DGM profiles followed a nutrient-type distribution in the slope zone, where water depth was deeper than 300 m. Statistical analyses using kr, composition and concentration of dissolved organic matter, and nutrient concentrations are currently in progress. It is expected that a potential link between seawater characteristics and kr will be obtained when the statistical analysis is complete.