HR: 1340h
AN: A23C-1476    [Abstracts]
TI: Contribution of Dust Particles to the Heterogeneous Removal of Acidic Gases From the Atmosphere During the MIRAGE Experiment
AU: * Hodzic, A
EM: alma@ucar.edu
AF: National Center for Atmospheric Research, Atmospheric Chemistry Division, Boulder, CO 80301, United States
AU: Flocke, F M
EM: ffl@ucar.edu
AF: National Center for Atmospheric Research, Atmospheric Chemistry Division, Boulder, CO 80301, United States
AU: Madronich, S
EM: sasha@ucar.edu
AF: National Center for Atmospheric Research, Atmospheric Chemistry Division, Boulder, CO 80301, United States
AU: Fast, J
EM: jerome.fast@pnl.gov
AF: Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, United States
AU: Zheng, W
EM: zheng@ucar.edu
AF: National Center for Atmospheric Research, Atmospheric Chemistry Division, Boulder, CO 80301, United States
AU: Weinheimer, A
EM: weinheimer@ncar.edu
AF: National Center for Atmospheric Research, Atmospheric Chemistry Division, Boulder, CO 80301, United States
AU: Montzka, D
EM: montzka@ucar.edu
AF: National Center for Atmospheric Research, Atmospheric Chemistry Division, Boulder, CO 80301, United States
AU: Knapp, D
EM: david@ucar.edu
AF: National Center for Atmospheric Research, Atmospheric Chemistry Division, Boulder, CO 80301, United States
AU: Mauldin, L
EM: mauldin@ncar.edu
AF: National Center for Atmospheric Research, Atmospheric Chemistry Division, Boulder, CO 80301, United States
AU: Wennberg, P
EM: wennberg@gps.caltech.edu
AF: California Institute of Technology, 1200 East California Bouldevard, Pasadena California, CA 91125, United States
AU: Crounse, J D
EM: crounjd@caltech.edu
AF: California Institute of Technology, 1200 East California Bouldevard, Pasadena California, CA 91125, United States
AU: McCabe, D
AF: California Institute of Technology, 1200 East California Bouldevard, Pasadena California, CA 91125, United States
AU: Clarke, A
EM: tclarke@soest.hawaii.edu
AF: University of Hawaii, 1000 Pope Road, Honolulu, HI 96822, United States
AU: Hostetler, C A
EM: Chris.A.Hostetler@nasa.gov
AF: NASA Langley Research Center, MS 435, Hampton, VA 23681, United States
AU: Hair, J W
EM: Johnathan.W.Hair@nasa.gov
AF: NASA Langley Research Center, MS 435, Hampton, VA 23681, United States
AB: The significance of the removal of acidic trace gases via heterogeneous processes, and its influence on the regional budget of several aerosol and gas-phase pollutants, is investigated downwind of Mexico City. According to experimental studies, the uptake of HNO3 onto reactive dust components, such as calcium and magnesium carbonates, results in an irreversible repartitioning of nitrate to a more stable particle phase and represent an important sink for nitrogen oxide species. These reactions are rarely considered in chemistry-transport models, and here we investigate how they can affect models" ability to predict the oxidizing potential of the atmosphere (NOx to NOy ratio), the atmospheric ozone balance, and coarse nitrate aerosol formation. Results from the MIRAGE field campaign show a tendency of lower HNO3 to NOy ratios with increasing dust loading in the Mexico City plume. In general, the HNO3 fraction of total NOy often does not increase with distance from the city which would be expected from gas-phase chemical processing. This evidence for heterogeneous removal is corroborated by ground-based measurements performed during MILAGRO indicating that mineral dust is often associated with coarse nitrate. We introduce this heterogeneous reaction in the WRF-CHEM model and analyze its impact on the formation of nitrogen oxide species, ozone, and coarse aerosol components, by comparison of model simulations with ground and airborne measurements in the vicinity of Mexico City. Several values of the nitric acid uptake coefficient are tested in order to investigate the sensitivity to this parameter. Model performance in simulating nitrates is evaluated with and without the heterogeneous reactions included.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting