Effect of Diesel Particles on the Photooxidation of a Diluted Diesel Exhaust-Toluene Mixture

To investigate the effect of diesel particles on photooxidation of ambient air, captive-air irradiation experiments were carried out by using indoor smog chambers. The formation of ozone and secondary aerosols due to photooxidation became weak probably due to high NO_x concentration when diesel exhaust was added to filtered ambient air. Addition of toluene to a diluted diesel exhaust mixture made it possible to enlighten the seed effect of diesel particles during the photooxidation reaction. When the initial number concentration of diesel particles was relatively low, the new particle formation in a diesel exhaust/toluene mixture due to photooxidation was exciting. However, after early formation and subsequent growth of particles, enough surface area of the particles suppressed new particle formation.