An outdoor smog chamber and modeling study of toluene-NOₓ photooxidation

An experimental investigation of the gas-phase photooxidation of toluene–NOₓ–air mixtures at part-per-million concentrations has been carried out in a 65-m³, outdoor smog chamber to assess our understanding of the atmospheric chemistry of toluene. In addition, six CO-NOₓ–air irradiations were conducted to characterize the chamber with regard to any wall radical sources. Measured parameters in the toluene–NOₓ experiments included O₃, NO, NO₂, HNO₃, peroxyacetyl nitrate (PAN), CO, toluene, benzaldehyde, o-cresol, m-nitrotoluene, peroxybenzoyl nitrate (PBZN), temperature, relative humidity, aerosol size distributions, and particulate organic carbon. Predictions of the reaction mechanism of Leone and Seinfeld [7] are found to be in good agreement with the data under a variety of initial conditions. Additional simulations are used to investigate various mechanistic pathways in areas where our understanding of toluene chemistry is still incomplete.