Collaborative Research on Snow and Ice Processes in the Deposition and Fate of Mercury in the Arctic

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Atmospheric mercury enters the arctic ecosystem through a set of complex atmospheric chemical reactions that require sea ice and leads to provide reactive bromine, low ambient temperatures, and enough sunlight for photolysis. As a consequence, virtually all atmospheric mercury entering the arctic ecosystem is initially deposited in the snow pack, both on land and at sea. Up to one third of this initial deposit is re-emitted to the atmosphere before the snow melts, but the remainder ends up in snow melt run-off. The fate of this water-borne mercury is uncertain and undoubtedly different on land vs. sea ice. Two key unanswered questions are: How much of the elemental mercury initially deposited is converted to toxic methyl-mercury, and where does this methylmercury ultimately come to rest? Since cryospheric processes related to snow and ice in large measure determine the answers to these questions, this work sets out to study these processes. The processes studied straddle the Arctic Coast, have pan-Arctic significance, and have a direct impact on human and ecosystem health. The project has experimental and synthesis components. Along a transect from the Chukchi Sea inland to Barrow and Atqasuk, measurements will be taken of reactive bromine and mercury loading in the snow pack. Detailed observations will be made during mercury depletion events and during the snowmelt, comparing and contrasting the fate of mercury on land with that at sea. Post snowmelt samples from tundra, lakes, ice, and terrestrial and marine sediments will be analyzed and used to determine where and how much of the deposited mercury is converted to methyl mercury. Manipulation experiments will be used to better understand how mercury is entrained in the snow pack, and how it is released during the snowmelt. A series of weeklong retreats by the research team and selected others will be held to produce a synthesis of the Arctic Mercury System. By understanding and modeling the arctic mercury system, the group will assess how the impact of mercury pollution on human and biological systems is likely to be affected by the unprecedented changes in sea ice and snow conditions that are taking place in the Arctic today. Intellectual Merit of Proposed Activity: The research fills a gap in our current understanding of the Arctic Mercury System, namely what happens to atmospheric mercury after it is deposited. It also serves as a bridge, connecting detailed studies of atmospheric chemistry of mercury deposition with the large body of studies related to arctic mercury environmental loading and health risk. This work takes a systems approach to the mercury problem that is both essential and novel. Broader Impacts: Mercury is toxic and of great concern to arctic residents and officials. Results from this research will be useful in assessing how arctic mercury pollution is derived from global levels of mercury, and how that pollutant loading might respond to changes in sea ice and snow conditions. Results will be communicated to decision-makers and the public in a series of outreach activities that include traditional graduate student training, conference presentations, website publication, classroom visits, and through the production and publication of a children's book by an award-winning author.