HR: 11:20h
AN: A22C-05    [Abstracts]
TI: Photochemical HCHO and H$_{2}$O$_{2}$ Processing in Snow at Summit, Greenland, and at South Pole
AU: * Hutterli, M A
EM: manuel@hwr.arizona.edu
AF: Department of Hydrology and Water Resources, The University of Arizona 1133 E. North Campus Dr., Tucson, AZ 85721 United States
AU: * Hutterli, M A
EM: manuel@hwr.arizona.edu
AF: Physics Institute, University of Bern Sidlerstrasse 5, Bern, CH-3012 Switzerland
AU: Burkhart, J F
EM: jburkhart@ucmerced.edu
AF: Department of Hydrology and Water Resources, The University of Arizona 1133 E. North Campus Dr., Tucson, AZ 85721 United States
AU: Friel, D K
EM: frieldo@bc.edu
AF: Department of Hydrology and Water Resources, The University of Arizona 1133 E. North Campus Dr., Tucson, AZ 85721 United States
AU: Frey, M M
EM: mfrey@hwr.arizona.edu
AF: Department of Hydrology and Water Resources, The University of Arizona 1133 E. North Campus Dr., Tucson, AZ 85721 United States
AU: Albert, M R
EM: Mary.R.Albert@erdc.usace.army.mil
AF: Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, NH 03755 United States
AU: Lefer, B
EM: blefer@uh.edu
AF: Department of Geosciences, University of Houston 312 SRB-1, 4800 Calhoun Road, Houston, TX 77204 United States
AU: Bales, R C
EM: rbales@ucmerced.edu
AF: University of California, Merced, P.O. Box 2039, Merced, CA 95344 United States
AB: Heterogeneous photochemistry and temperature-driven recycling of formaldehyde (HCHO) and hydrogen peroxide (H$_{2}$O$_{2}$) in snow can significantly alter the composition of both the snow and the overlying atmospheric boundary layer. This has important consequences for the interpretation of ice-core records to understand the past oxidizing capacity of the atmosphere, as well as for the basic understanding of gas-phase photochemistry above snowpacks. Previous field and laboratory experiments combined with physically based air-snow transfer modeling showed that temperature-driven uptake and release explains at least 75% if not all of the observed net snow-air fluxes of both species at Summit, Greenland and South Pole, Antarctica. Other studies indicated that, at least for HCHO, some of the observed net flux is due to photochemical production in the snow. However, its actual contribution to the total observed flux from snowpacks into the boundary layer has not yet been quantified. Here we present new HCHO and H$_2$O$_2$ data from 2 field campaigns at Summit, Greenland, in summer 2003 and spring 2004 and from the ANTCI field campaign at South Pole in December 2003. Both species were measured in ambient air, and in firn air drawn from various depths in the snowpack while a large area of the snowpack (4m$^{2}$) was intermittently shaded. Filters of various transmittances of UV radiation were used during the shading experiments in order to separate the impact of changing temperature and radiation on the firn-air mixing ratios. In addition, profiles of temperature, radiation, and concentrations of HCHO and H$_{2}$O$_{2}$ in the snow phase were measured. Combined with new modeling studies, these data are used to quantify the relative importance of both, UV and temperature on firn air mixing ratios and snow-air fluxes for the wide range of conditions encountered at both locations and during different times of the year.
DE: 9310 Antarctica
DE: 9315 Arctic region
DE: 1863 Snow and ice (1827)
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting