Kinetics of the gas-phase reactions of hydroxyl radicals with C₁-C₆ aliphatic alcohols in the presence of ammonium sulfate aerosols

The effects of ammonium sulfate aerosols on the kinetics of the hydroxyl radical reactions with C₁-C₆ aliphatic alcohols have been investigated using the relative rate technique. P-xylene was used as a reference compound for the C₂-C₆6 aliphatic alcohols study, and ethanol was used as a reference compound for the methanol study. Two different aerosol concentrations that are typical of polluted urban conditions were tested. The total surface areas of aerosols were 1400 μm² cm^-3 (condition I) and 3400 μm² cm^-3 (condition II). Results indicate that ammonium sulfate aerosols promote the ethanol/OH radical and 1-propanol/OH radical reactions as compared to the p-xylene/OH radical reaction. The relative rate of the ethanol/·OH reaction versus the p-xylene/·OH reaction increased from 0.19 ± 0.01 in the absence of aerosols to 0.24 ± 0.01 and 0.26 ± 0.02 under aerosol conditions I and II, respectively. The relative rate of the 1-propanol/·OH reaction versus the p-xylene/·OH reaction increased from 0.45 ± 0.03 in the absence aerosols to 0.56 ± 0.02 and 0.55 ± 0.03 under aerosol conditions I and II, respectively. However, significant changes in the relative rates of the 1-butanol/·OH, 1-pentanol/·OH, and 1-hexanol/·OH reaction were not observed for either aerosol concentration. The relative rates of the methanol/·OH reaction versus the ethanol/·OH reaction were identical in the absence and presence of aerosols. These results indicate that ammonium sulfate aerosols promote the methanol/·OH reaction as much as the ethanol/·OH reaction (as compared to the p-xylene/·OH reaction).