Effects of fine aerosol composition on the rate constants of OH initiated gas-phase reactions

The effects of atmospheric aerosols on the gas-phase reactions of OH radicals with organic compounds were studied. Three different types of organics were selected, i.e., alkane (n-hexane), aromatics (p-xylene), and oxygenate (1-propanol). The relative rates calculated using the recommended rate constants were 0.99, 0.39, and 0.39 for 1-propanol/n-hexane, n-hexane/p-xylene, and 1-propanol/p-xylene, respectively. The relative rate increased by ≈ 26%, from 0.85 in the absence of aerosols, to 1.07 in the presence of ammonium sulfate aerosols, indicating that ammonium sulfate aerosols promoted significantly the reaction of 1-propanol with OH radicals as compared to n-hexane. No influence on the relative rate of n-hexane/p-xylene was observed. The influence of aerosol on tropospheric reactions depended on both the aerosol composition and the type of organic compound.