Effect of Initial Toluene Concentration on the Photooxidation of Toluene-NOx-Air Mixture - II. Aerosol Formation and Growth

An experimental investigation of the gas-phase photooxidation of toluene-NOx-air mixtures at sub-ppm concentrations has been carried out in a 6.9 m(3), indoor smog chamber irradiated by blacklights. Measured parameters in the toluene-NOx, experiments included aerosol, O-3, NO, NO2, NOx, CO, SO2, toluene, and air temperature. The initial toluene concentration ranged from 225 ppb to 991 ppb and the initial concentration ratio of toluene/NOx, in ppbC/ppb was in the range of 5 similar to 20. It was found that the variation of aerosol number concentration with irradiation time caused by the photooxidation of toluene-NOx-air mixtures depended on the initial toluene concentration for similar concentration ratio of toluene/NOx. The dependency of initial toluene concentration on the photooxidation of toluene-NOx-air mixtures for toluene/NOx = 5 similar to 6 seemed to be opposite to that for toluene/NOx = 10 similar to 11. The maximum number concentration of aerosols formed by photooxidation and the aerosol yield depended on both initial toluene concentration and initial concentration ratio of toluene/NO,. In this study, the aerosol yield, defined as aerosol formed per unit toluene consumed, was found to be 0.01 similar to 0.16.