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

The effects of (NH4)(2)SO4, NH4NO3, NaCl, NH4CI, and Na2SO4 aerosols on the kinetics of l-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 mum(2) cm(-3) (condition II). Results indicate that aerosols promote the oxidation of l-propanol, and the extents of the promoting effects depend on the aerosol composition and concentration. Increases in the relative rates of the l-propanol/(OH)-O-. reaction vs. the p-xylene/(OH)-O-. reaction were only observed for (NH4)(2)SO4 aerosol conditions I and II. NH4NO3 aerosol condition II, and NH4CL aerosol condition II. These results indicate that NH4+ is the species promoting the oxidation of l-propanol, and suggests the possibility of a strong interaction between NH4+ and l-propanol that can change the activation energy of the initial (OH)-O-. attack. These results have profound implications on the use of air quality models for the assessment of air pollution control strategies. (C) 2002 Elsevier Science Ltd. All rights reserved.