Laboratory studies of the impact of aerosol composition on the heterogeneous oxidation of 1-propanol

The effects of (NH 4) 2SO 4, NH 4NO 3, NaCl, NH 4Cl, and Na 2SO 4 aerosols on the kinetics of 1-propanol oxidation in the presence of the hydroxyl radical have been investigated using the relative rate technique. p-Xylene was used as a reference compound. Two different aerosol concentrations that are typical of polluted urban conditions were tested. The total surface areas of aerosols were 1400 (condition I) and 3400 μm 2 cm −3 (condition II). Results indicate that aerosols promote the oxidation of 1-propanol, and the extents of the promoting effects depend on the aerosol composition and concentration. Increases in the relative rates of the 1-propanol/ OH reaction vs. the p-xylene/ OH reaction were only observed for (NH 4) 2SO 4 aerosol conditions I and II, NH 4NO 3 aerosol condition II, and NH 4Cl aerosol condition II. These results indicate that NH 4 + is the species promoting the oxidation of 1-propanol, and suggests the possibility of a strong interaction between NH 4 + and 1-propanol that can change the activation energy of the initial OH attack. These results have profound implications on the use of air quality models for the assessment of air pollution control strategies.