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Formation of Reactive Gaseous Mercury in the Arctic: Evidence of Oxidation of Hg0 to Gas-Phase Hg-II Compounds After Arctic Sunrise

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Abstract: We have measured total gaseous mercury concentrations (Hgo) at Point Barrow, Alaska since September 1998 in an effort to determine the geographic extent and reaction mechanism of the so-called mercury depletion events (MDE) previously reported in the high Arctic at Alert, Canada. Hgo has been sampled now for nearly 2 years at Barrow. In September, 1999, we began making the first automated measurements of reactive gaseous mercury (RGM) attempted in the Arctic, along with measurements of Hg accumulation in snowpack to determine the fate of the "depleted" Hgo. During the fall and early winter, Hgo and RGM exhibit only minor variation, Hgo remaining within ~10% of global background, near 1.6-1.8 ng/m3. The MDE periods are quite different, however; within days of Arctic sunrise in January, Hgo exhibits major variations from the mean, rapidly dropping as low as 0.05 ng/m3 and then cycling back to typical levels, sometimes exceeding global background. These events continue throughout Arctic spring, then end abruptly following snowmelt, in early June. Prior to Arctic sunrise, RGM remains near detection (<2 pg/m3), but after sunrise increases dramatically (to levels as high as 900 pg/m3) in synchrony with the "depletion" of Hgo. Both phenomena exhibit a strong diel cycle, in parallel with UV-B. We conclude that MDE's involve rapid in-air oxidation of Hgo to a species of RGM by photochemically-driven reactions, probably involving the same reactive bromine and chlorine compounds involved in ozone destruction. Sharp increases in Hg in the surface snowpack after sunrise coincident with periods of peak RGM suggest surface accumulation of the RGM by dry deposition.

This article has been subjected to Agency review and approved for publication.
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Citation:Lindberg, S. E., S. Brooks, C. J. Lin, K. Scott, T. Meyers, M. S. Landis, and R. K. Stevens. Formation of Reactive Gaseous Mercury in the Arctic: Evidence of Oxidation of Hg0 to Gas-Phase Hg-II Compounds After Arctic Sunrise. WATER, AIR AND SOIL POLLUTION:FOCUS 1(5-6):295-302, (2001).
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Contact: Liz Hope - (919) 541-2785 or hope.elizabeth@epa.gov
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Division: Human Exposure & Atmospheric Sciences Division
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Branch: Source Apportionment & Characterization Branch
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Product Type: Journal
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Published: 04/01/2001
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Related Entries:
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Bullet Item Atmospheric Mercury Research
spacer Relationship Reason:   A Project of the Product
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Last Updated on Monday, October 22, 2007
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