HR: 0830h
AN: A51F-0741    [PDF]
TI: Uptake of Acetic Acid on Ammonium Nitrate
AU: * Shilling, J E
EM: john.shilling@colorado.edu
AF: Department of Chemistry and Biochemistry and CIRES, University of Colorado, Boulder, Campus Box 216 CIRES Room 318, Boulder, CO 80309 United States
AU: Tolbert, M A
EM: tolbert@spot.colorado.edu
AF: Department of Chemistry and Biochemistry and CIRES, University of Colorado, Boulder, Campus Box 216 CIRES Room 318, Boulder, CO 80309 United States
AB: The interaction of acetic acid with thin ammonium nitrate films has been studied using a Knudsen flow reactor equipped with FTIR-RAS (Reflection Absorption Spectroscopy). Initial sticking coefficients ($\gamma$'s) and coverages ($\Theta$'s) were determined over the temperature range 200 to 240 K. In the absence of water vapor (RH $<$ 1%), the uptake saturated with coverages ranging from $\Theta$ = 5.0 x 10$^{16}$ molecules/cm$^{2}$ at 200 K to $\Theta$ = 1.2 x 10$^{14}$ molecules/cm$^{2}$ at 240 K. The initial uptake coefficient varied from $\gamma$ = 0.069 to $\gamma$ = 0.0019 for temperatures from 200 to 240 K, respectively. The IR spectra show that acetic acid ionized on the surface, despite the fact that the ammonium nitrate film was effloresced. Adding water vapor to the chamber resulted in continuous uptake and dramatically increased coverages. The IR spectra again revealed that acetic acid ionized on the surface. These results suggest that organic acids may be readily adsorbed onto inorganic aerosol particles under tropospheric conditions.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting