Distribution of mercury species in the Western Arctic Ocean (U.S. GEOTRACES GN01)

Abstract Mercury (Hg) in the Arctic Ocean is a concern due to unusually high concentrations of monomethylmercury (MMHg) in fish and marine animals. Increased human exposure from consumption of these animals is a significant health concern that is related to Hg contamination in nature. Most Arctic marine Hg research has investigated the amounts, distributions, and cycling in animals, snow, and ice, while few studies have examined the aqueous behavior and fate of Hg in the polar ocean. Here we present the most comprehensive dataset detailing Hg speciation and distribution of elemental Hg (Hg 0 ), dimethylmercury (DMHg), and filtered and particulate total Hg and MMHg in the western Arctic Ocean. This data was obtained as part of the U.S. Arctic GEOTRACES cruise (GN01) in 2015. Many water masses sampled appeared to be enriched with anthropogenic Hg. The Transpolar Drift supplied HgT and Hg 0 to the central Arctic Ocean, but not methylated Hg. Gaseous Hg 0 , but not DMHg, was elevated in surface waters under the ice cover. Monomethylmercury levels, which averaged 0.054 ± 0.050 pM, are lower than other major ocean basins, suggesting ambient MMHg levels in western Arctic Ocean seawater do not by themselves explain anomalously high Hg in Arctic animals.