HR: 0800h
AN: A51E-0840    [Abstracts]
TI: Laboratory Study of the Physical Chemistry of (NH$_{4}$)$_{2}$SO$_{4}$/H$_{2}$SO$_{4}$/H$_{2}$O: Implications for Cirrus Cloud Formation
AU: * Beyer, K D
EM: Beyer.Keit@uwlax.edu
AF: University of Wisconsin - La Crosse, 105 Graff Main Hall, La Crosse, WI 54601 United States
AU: Burrmann, N
EM: Nicola_Burrmann@wlc.edu
AF: Wisconsin Lutheran College, 8800 W. Bluemound Rd., Milwaukee, WI 53226 United States
AB: Aqueous atmospheric aerosols have been known to contain ammonium and sulfate ions in varying ratios for some time. These three components constitute a ternary system whose molecular makeup consists of ammonium sulfate (high ammonium content), sulfuric acid (high sulfate content) and water. We have studied the ammonium sulfate/sulfuric acid/water system using differential scanning calorimetry (DSC) and infrared spectroscopy of thin films at low temperatures. Previous work on this system explored the phase diagram from 273 K to 373 K, leaving the low-temperature portion of the phase diagram undiscovered. Some work has focussed on only one slice of this system: ammonium bisulfate/water. We have constructed the temperature-contour ternary phase diagram for ammonium sulfate/sulfuric acid/water. From our results, it is clear there are several binary subsystems: letovicite/water and ammonium bisulfate/SAT, among others. However, we have clear evidence that ammonium bisulfate/water is not a binary system that exists. Rather it is a slice through the ternary system and thus is much more complex, and can not be represented by a simple ammonium bisulfate/water binary phase diagram. Implications of our results on understanding cirrus cloud formation will be discussed.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting