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(227) Atmospheric mercury deposition during the last 270 years: a glacial ice core record of natural and anthropogenic sources.
Schuster, Paul*,1, Krabbenhoft, David2, Naftz, David3, Cecil, DeWayne4, Olson, Mark2, DeWild, John2, Susong, David3, Green, Jaromy4, Abbott, Micheal5, 1 U.S. Geological Survey, Boulder, CO, USA2 U.S. Geological Survey, Madison, WI, USA3 U.S. Geological Survey, Salt Lake City, UT, USA4 U.S. Geological Survey, Idaho Falls, ID, USA5 Geosciense Research, INEEL, Idaho Falls, ID, USA
ABSTRACT- Mercury (Hg) contamination of aquatic ecosystems and subsequent methyl mercury bioaccumulation are significant environmental problems of global extent. At regional to global scales, the primary mechanism of Hg contamination is atmospheric Hg transport. Thus, a better understanding of the long-term history of atmospheric Hg cycling and quantification of the sources is critical for assessing the regional and global impact of anthropogenic Hg emissions. Ice cores collected from the Upper Fremont Glacier (UFG), Wyoming, U.S.A. contain a high-resolution record of total atmospheric Hg deposition (circa 1720-1993). Total Hg in 97 ice-core samples was determined with trace-metal clean handling methods and low-level analytical procedures to reconstruct the first and most comprehensive atmospheric Hg deposition record of its kind yet available from North America. The record indicates major atmospheric releases of both natural and anthropogenic Hg from regional and global sources. Integrated over the past 270-year ice-core history, anthropogenic inputs contributed 52 percent, volcanic events 6 percent, and background sources 42 percent. More significantly, during the last 100 years, anthropogenic sources contributed 70 percent of the total Hg input. Unlike the 2 to 7-fold increase observed from pre-industrial times (before 1840) to the mid 1980s in sediment-core records, the UFG record indicates a 20-fold increase for the same period. The sediment-core records, however, are in agreement with the last 10 years of this ice core record indicating declines in atmospheric Hg deposition.
Key words: mercury, deposition, ice core, record
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