Abstract
The photooxidation of aromatic hydrocarbons (AHCs) is one of the potential sources of secondary organic aerosol (SOA) in urban air, but the explicit reaction mechanisms of these SOA formations have not been elucidated. In this study, we measured SOA yields during oxidation of four AHCs from a series of laboratory experiments. The SOA yields from toluene, p-ethyltoluene, p-xylene and 1,3,5-trimethylbenzene were 0.07-0.11, 0.06-0.10, 0.02-0.04 and 0.02-0.03, respectively; the SOA yield from each AHC depended on the initial AHC concentration. On the basis of a previous reaction mechanism, in which condensable products are assumed to be formed by secondary reactions of primary oxidation products with ozone, the SOA concentrations were calculated and compared with the experimental results. As for each AHC, SOA yields measured at different initial AHC concentrations could be explained by assuming that the overall yield of primary oxidation products which forms SOA is constant being independent of the initial AHC concetration.
