Organosulfate Formation in the Submicron Organic Aerosol Internally Mixed with Sulfuric Acid

Jiaying Li (1), Myoseon Jang (1)

(1) Department of Environmental Engineering Sciences, University of Florida

     Abstract Number: 151
     Last modified: April 25, 2010

Abstract
Organosulfate (OS) was produced in the sulfuric acid aerosol internally mixed with glyoxal or glycerol using an indoor Teflon film chamber and analyzed for aerosol acidity with colorimetry integrated with reflectance UV-Visible spectrometer (C-RUV) and for sulfate concentrations using a Particle-into-liquid-sampler Ion chromatography (PILS-IC). Fourier transform infrared spectroscopy (FTIR) equipped with a small flow chamber that holds an optical window for the internally mixed particle samples impacted on a silica window was used to characterize aerosol compositions. The reduction of the intensity of OH stretching bands in FTIR data indicates the OS formation in aerosol and increase in the hydrophobic property of aerosol. The decreases of aerosol acidity measured by C-RUV indicated that the aerosol-phase reaction of sulfuric acid with glyoxal or glycerol completed within 80 minutes leading greater than 70% of OS yields under relative humidity ranging from 20 to 70%. Compared to the concentration of non-organosulfate sulfates calculated from FTIR and SMPS data, PILS-IC data indicates that a high fraction of the aerosol-phase OS collected in water return to parent compounds (e.g., 99% for glyoxal-sulfuric acid and 58% for glycerol-sulfuric acid) due to reversibility of OS products. Unlike the reaction of an organic compound with highly acidic sulfuric acid solution, which is studied using a proton nuclear magnetic resonance ($^1H-NMR), our studies for in situ aerosol characterization showed that OS formation is considerably fast and efficient due to not only the large surface area to volume ratio of submicron aerosols by which water can evaporate quickly from the aerosol but also the phase transition from gel to sol as aerosol-phase reactions progress.