Contributions of Toluene and [alpha]-Pinene to SOA Formed in an Irradiated Toluene/[alpha]-Pinene/NO^sub x^/ Air Mixture: Comparison of Results Using ^sup 14^C Content and SOA Organic Tracer Methods

An organic tracer method, recently proposed for estimating individual contributions of toluene and α-pinene to secondary organic aerosol (SOA) formation, was evaluated by conducting a laboratory study where a binary hydrocarbon mixture, containing the anthropogenic aromatic hydrocarbon, toluene, and the biogenic monoterpene, α-pinene, was irradiated in air in the presence of ... to form SOA. The contributions of toluene and cα-pinene to the total SOA concentration, calculated using the organic tracer method, were compared with those obtained with a more direct ... content method. In the study, SOA to SOC ratios of 2.07 ± 0.08 and 1.41 ± 0.04 were measured for toluene and α-pinene SOA, respectively. The individual tracer-based SOA contributions of 156 ... for toluene and 198 ... for α-pinene, which together accounted for 82% of the gravimetrically determined total SOA concentration, compared well with the ... values of 182 and 230 ... measured for the respective SOA precursors. While there are uncertainties associated with the organic tracer method, largely due to the chemical complexity of SOA forming chemical mechanisms, the results of this study suggest the organic tracer method may serve as a useful tool for determining whether a precursor hydrocarbon is a major SOA contributor. (ProQuest-CSA LLC: ... denotes formulae/symbols omitted.)