Mercury Contamination and Biogeochemical Cycling in the Arctic

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AbstractOPP-9908895FitzgeraldLimited knowledge exists on atmospheric, terrestrial and marine cycling of mercury in the polar regions or on the impact from pollution-derived mercury The atmosphere is the principle route by which mercury is transferred at the Earth's surface. The major species transported is elemental mercury (Hg0) which has an atmospheric residence time of one-two years. Therefore, natural and anthropogenic mercury can be readily dispersed intra- and inter-hemispherically, including the Arctic.The Principal Investigator will address four hypotheses: 1) the remote U.S. Arctic region has been affected by increases in mercury contamination similar to that observed in other remote regions; 23 oligotrophic Arctic lakes have significant evasional losses of mercury, especially Hg0 if these lakes behave like temperate lacustrine systems, then in-situ Hg0 production and emission will be favored by high pH, higher reactive levels mercury levels and a greater in-situ supply of reducing agents; 3) the linear correlation between mercury and 210Pb found in Arctic rainwater from other locations is observed in the Arctic and this behavior can be used to constrain wet atmospheric flux of mercury to lakes and watersheds; 4) Hg0 is the predominant mercury cycling product in the oxic zone of the Arctic lakes, net in-situ synthesis of monomethylmercury (MMHg) is most significant in redox zones transition zones.The Principal Investigator will develop an experimental design which includes extensive field and laboratory investigations. These activities are divided into four categories: 1) atmospheric mercury deposition and speciation deterininations; 2) sediment core collection, mercury analysis and geochronology using 210Pb dating; 3) in-lake mercury speciation and cycling studies; and 4) laboratory simulations and incubation experiments. This research should provide high quality biogeochemcial data needed for quantitative assessment of the human-related mercury emissions over the past 150 years. It should help to decipher current and historic evidence of the impact from this deposition as reflected by MMHg production and accumulation in aquatic ecosystems and amplification in the natural re-emission of mercury from water sources due to the presence of pollutant-derived mercury. This information will improve models of the global.and regional biogeochernical cycling of mercury and assessing the impact associated with pollutant-derived mercury in the environment.