HR: 0800h
AN: A21A-0835    [Abstracts]
TI: Uptake of CF3COOH in Upper Tropospheric Sulfate Particles: Effects of Fluorination on the Accommodation of Oxygenated Organic Vapors.
AU: * Sulbaek Andersen, M P
EM: mads@sulbaek.dk
AF: University of Copenhagen, Department of Chemistry (KLV) Universitetsparken 5, Copenhagen, 2100 Denmark
AU: Nielsen, O J
EM: ojn@kiku.dk
AF: University of Copenhagen, Department of Chemistry (KLV) Universitetsparken 5, Copenhagen, 2100 Denmark
AU: Michelsen, R R
EM: miche033@umn.edu
AF: NASA Ames Research Center, Atmospheric Chemistry and Dynamics Branch, Moffett Field, CA 94035 United States
AU: Iraci, L T
EM: liraci@mail.arc.nasa.gov
AF: NASA Ames Research Center, Atmospheric Chemistry and Dynamics Branch, Moffett Field, CA 94035 United States
AB: Recognition of the adverse impact of chlorofluorocarbon (CFC) release into the atmosphere has led to an international effort to replace CFCs with environmentally acceptable alternatives. Laboratory studies indicate that some of these, including HFC-134a, degrade to yield trifluoroacetyl halides of the form CF₃C(O)X. Hydrolysis of trifluoroacetyl halides in cloud water is expected to form trifluoroacetic acid (TFA). Although TFA is produced in aqueous phase chemistry, is highly soluble and also partitions into the water phase, the evaporation of cloud droplets can relocate TFA to the gas phase where it can react with OH radicals. Still this reaction is slow and can only account for to account for <10-20% of the tropospheric loss of TFA. The main atmospheric fate of TFA is believed to be wet and dry deposition to the surface.
Submicrometer aerosol particles are ubiquitous in the upper troposphere where they drive such processes as cloud droplet condensation and scattering of incoming solar radiation, and have impact on regional and global climate. While these particles are known to be predominantly sulfuric acid solutions, neutralized with different amounts of ammonia depending on their location and history, their trace composition is largely uncertain. Organic species may be the controlling factor in many processes of interest, and thus identifying organic components and their sources is important for understanding the role of aerosols in the troposphere. While studies show that cloud and fog water will act as a sink for atmospheric TFA, an accurate knowledge of the Henry's law coefficient is required to assess gas/liquid partitioning in upper tropospheric sulfate aerosols, where the temperature and liquid phase pH is much lower.
The purpose of this work is to evaluate the role of upper tropospheric sulfate aerosols as a potential sink for TFA, and more generally, the effects of fluorine substitution on uptake of organic compounds into upper tropospheric aerosols. We have measured the solubility of gaseous acetic acid (CH₃C(O)OH), and TFA (CF₃C(O)OH) in cold sulfuric acid solutions over ranges of temperature (210-245 K) and acid composition (40-75 wt% H₂SO₄).
The determining factors in the accumulation of organic material into sulfate particles in the UT/LS are discussed and the possibility of upper tropospheric sulfate aerosols to act as a global sink for TFA is evaluated.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005