HR: 0800h
AN: A51C-0576    [Abstracts]
TI: A Multiphase Study of the Chemical Composition of Air, Aerosol Particles, Snow, and Ice Forms Collected Near Barrow, Alaska Provides Information on Bromine Activation
AU: * Alvarez-Aviles, L
EM: ftla@uaf.edu
AF: University of Alaska Fairbanks, PO Box 753302, Fairbanks, AK 99775, United States
AU: Simpson, W R
EM: ffwrs@uaf.edu
AF: University of Alaska Fairbanks, PO Box 753302, Fairbanks, AK 99775, United States
AU: Carlson, D A
EM: fsdac8@uaf.edu
AF: University of Alaska Fairbanks, PO Box 753302, Fairbanks, AK 99775, United States
AU: Sturm, M
EM: msturm@crrel.usace.army.mil
AF: 2. US Army Cold Regions Research and Engineering Laboratory, P.O. Box 35170, Fairbanks, AK 99703, United States
AU: Douglas, T A
EM: Thomas.A.Douglas@erdc.usace.army.mil
AF: 2. US Army Cold Regions Research and Engineering Laboratory, P.O. Box 35170, Fairbanks, AK 99703, United States
AU: Laskin, A
EM: Alexander.Laskin@pnl.gov
AF: W. R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O.Box 999, MSIN K8-88, Richland, WA 99352, United States
AB: Unique chemistry that releases halogens from sea salts into the atmosphere depletes ozone and deposits mercury in the springtime in the Arctic. It is believed that Br⁽-) is present in the snow pack and other ice reservoirs over the ice-covered ocean during winter, and is liberated by poorly understood chemistry in the springtime. We undertook a study of halogens in different ice reservoirs like snow, aerosol particles, and in the gas phase in the vicinity of Barrow, Alaska in the springtime of 2007. For the first time, we observed a time series of most of the relevant bromine reservoirs simultaneously. The size and time-resolved aerosol data help us to complete a picture of what ice reservoirs are involved in releasing Br⁽-) into the gas phase. The smallest particles sampled with a 3-stage DRUM impactor contain a larger fraction of sulfate than the larger particles, and probably are the result of Arctic Haze sulfate pollution overlaid on a background of mostly larger sea-salt particles. The smallest particles are mostly enhanced in Br⁽-) (as compared to sea salt reference) while larger-sized particles could show near sea-salt Br⁽-) enrichment factors or slight Br- depletions. Enhancement in Br⁽-) can come from termination of halogen activation chemistry, which produces HBr. These HBr molecules would then be scavenged efficiently by the smaller particles due to their high surface area, which is consistent with our data. Depletion of Br⁽-) indicates halogen activation to the gas phase. During halogen activation events, surface snow shows higher depletions than the aerosol particles. Because the surface snow received its salts from the sea-salt aerosol that is mostly enhanced in Br⁽-) or is comparable to sea salt, and we observe depletions in snow, this indicates that snowpack is releasing halogens to the atmosphere. Knowing what ice surfaces contribute more to active Br⁽-) species can help us to predict ozone depletion and mercury deposition events. This mechanistic understanding is needed to make meaningful predictions of how Arctic pollution and Arctic atmospheric chemistry will respond to the drastic changes in sea ice.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0335 Ion chemistry of the atmosphere (2419, 2427)
DE: 0365 Troposphere: composition and chemistry
DE: 0736 Snow (1827, 1863)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting