HR: 15:10h
AN: A42E-07    [PDF]
TI: Ice Nucleation in Internally Mixed Ammonium Sulfate/Dicarboxylic Acid Particles
AU: * Wise, M E
EM: matthew.wise@colorado.edu
AF: Department of Chemistry and Biochemistry and CIRES, University of Colorado, Boulder, CIRES Rm #318 Campus Box #216, Boulder, CO 80309-0216 United States
AU: Garland, R M
EM: rebecca.garland@colorado.edu
AF: Department of Chemistry and Biochemistry and CIRES, University of Colorado, Boulder, CIRES Rm #318 Campus Box #216, Boulder, CO 80309-0216 United States
AU: Tolbert, M A
EM: margaret.tolbert@colorado.edu
AF: Department of Chemistry and Biochemistry and CIRES, University of Colorado, Boulder, CIRES Rm #318 Campus Box #216, Boulder, CO 80309-0216 United States
AB: Recent studies have shown that tropospheric sulfate aerosols commonly contain 50 % by mass organic species. The influence of these organics on the chemical and physical properties of sulfate aerosols is not fully established. We have determined the ice nucleation temperatures for particles composed of eutonic mixtures of ammonium sulfate with a series of dicarboxylic acids. Measurements of the low temperature vapor pressures of the eutonic solutions were also made in order to develop a calibration curve to convert the freezing temperatures to ice saturation ratios. We find that for a given water activity, the freezing temperature is constant and is independent of the mole fraction of organic in solution. While this observation was predicted by {\it Koop et al.} [2000], the freezing temperatures observed in the present study are somewhat higher than those found in the emulsion studies used to develop the {\it Koop et al.} [2000] theory.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting