Secondary organic aerosol formation from the gas phase reaction of hydroxyl radicals with m-, o- and p-cresol

Secondary organic aerosol (SOA) formation during the atmospheric oxidation of cresols was investigated using a large smog chamber (8000 L), at atmospheric pressure, 294±2 K and low relative humidity (6–10%). Cresol oxidation was initiated by irradiation of cresol/CH3ONO/NO/air mixtures. The cresol loss was measured by gas chromatography with a flame ionization detector (GC-FID) and the temporal evolution of the aerosol was monitored using a scanning mobility particle sizer (SMPS). The overall organic aerosol yield (Y) was determined as the ratio of the suspended aerosol mass corrected for wall losses (Mo) to the total reacted cresol concentrations assuming a particle density of 1.4 g cm−3. Analysis of the data clearly show that Y is a strong function of Mo and that SOA formation can be expressed by a one-product gas/particle partitioning absorption model. The aerosol formation is affected by the initial cresol concentration, which leads to aerosol yields from 9% to 42%. These results are in good agreement with a recent study performed on SOA formation from the photo-oxidation of o-cresol in a smog chamber. To our knowledge, the present work represents the first investigation of SOA formation from OH reaction with m- and p-cresol.