HR: 11:50h
AN: A22C-07    [Abstracts]
TI: Mercury Concentrations in Coastal and Inland Snow In Arctic Alaska
AU: * Douglas, T A
EM: thomas.a.douglas@erdc.usace.army.mil
AF: Cold Regions Research and Engineering Laboratory Alaska, P.O. Box 35170 Building 4070, Fort Wainwright, AK 99703 United States
AU: Sturm, M
EM: matthew.sturm@erdc.usace.army.mil
AF: Cold Regions Research and Engineering Laboratory Alaska, P.O. Box 35170 Building 4070, Fort Wainwright, AK 99703 United States
AU: Simpson, W R
EM: ffwrs@aurora.uaf.edu
AF: Department of Chemistry and Geophysical Institute University of Alaska-Fairbanks, PO Box 757320, Fairbanks, AK 99775-6160 United States
AU: Brooks, S B
EM: brooks@atdd.noaa.gov
AF: National Oceanic and Atmospheric Administration, Atmospheric Turbulence and Diffusion Division, 456 S. Illinois Avenue PO Box 2456, Oak Ridge, TN 37830 United States
AU: Lindberg, S E
EM: LindbergSE@ornl.gov
AF: Oak Ridge National Laboratory Environmental Sciences Division, PO Box 2008, Oak Ridge, TN 37831-6038 United States
AU: Perovich, D K
EM: donald.k.perovich@erdc.usace.army.mil
AF: Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, NH 03755 United States
AB: Elevated mercury concentrations in arctic coastal and inland snow have been reported at remote locations. This mercury is attributed to mercury depletion events (MDEs) where gas-phase mercury is depleted due to photochemical conversion to reactive gaseous mercury that is subsequently deposited to snow and ice surfaces. The high mercury concentrations are generally observed near the coast, suggesting that sea ice or leads play a role in MDEs. We sampled the snow pack during 250-km over snow traverses from the central Brooks Range north to the sea ice off of Barrow, Alaska in the spring of 2002 and in the spring of 2004. Our goal was to gain a better understanding of the spatial pattern of mercury concentrations in surface snow. Mercury concentrations in surface snow more than 200 km inland from the Arctic Ocean coast ranged from 5 to 25 ng/L. Samples of a layer of recently deposited snow between 75 km inland from Barrow and Barrow yielded mercury concentrations that ranged from 25 to 147 ng/L and were not correlated with distance from the coast. Snow samples obtained from locations on the sea ice yielded far greater mercury concentrations than terrestrial snow. Mercury concentrations of as high as 820 ng/L were measured in surface hoar snow forming at the edge of a 200 meter wide open lead. Recently formed frost flowers on nilas ice at the edge of a refreezing lead contained mercury in concentrations ranging from 150 to 185 ng/L. Our work yields two important results. First, the relationship between mercury concentrations in snow and distance from the coast is complex and non-monotonic. Second, large leads, those with convective plumes that drive vapor transport, most likely play an important but unresolved role in lower tropospheric MDE chemistry near the Arctic Ocean coast. The existence of highly elevated mercury concentrations near leads suggests the need for a more detailed investigation of the chemical and physical regime near leads.
DE: 1030 Geochemical cycles (0330)
DE: 0315 Biosphere/atmosphere interactions
DE: 0330 Geochemical cycles
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting