Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 4 2004 10.5194/acpd-4-4019-2004 http://www.atmos-chem-phys-discuss.net/4/4019/2004/ http://www.atmos-chem-phys-discuss.net/4/4019/2004/acpd-4-4019-2004.html http://www.atmos-chem-phys-discuss.net/4/4019/2004/acpd-4-4019-2004.pdf 4019 4038 2004-07-29 Enhanced uptake of water by oxidatively processed oleic acid A. Asad B. T. Mmereki D. J. Donaldson jdonalds@chem.utoronto.ca Department of Chemistry and Department of Physical and Environmental Sciences, University of Toronto, 80 St. George St., Toronto, M5S 3H6 Ont., Canada A quartz crystal microbalance apparatus has been used to measure the room temperature uptake of water vapour by thin films of oleic acid as a function of relative humidity, both before and following exposure of the films to various partial pressures of gas phase ozone. A rapid increase in the water-sorbing ability of the film is observed as its exposure to ozone is increased, followed by a plateau region in which no additional water is taken up. In this fully-processed region the mass of water taken up by the film is about 4 times that of the unprocessed film. Infrared spectra of the films, measured after variable exposures to ozone, show dramatic increases in both the "free" and hydrogen-bonded O-H stretching regions, and a decrease in the intensity of olefinic features. These results are consistent with the formation of an oxygenated polymeric product or products, as well as the gas phase products previously identified.