Secondary Organic Aerosol formation from phenolic compounds in the absence of NOx
1University of California, Riverside, Department of Chemical and Environmental Engineering, Riverside, California, USA
2College of Engineering – Center for Environmental Research and Technology (CE-CERT), Riverside, California, USA
*currently at: National Institute for Environmental Studies, Japan
Abstract. SOA formation from benzene, toluene, m-xylene, and their corresponding phenolic compounds were investigated using the UCR/CE-CERT Environmental Chamber to evaluate the importance of phenolic compounds as intermediate species in aromatic SOA formation. SOA formation yield measurements coupled to gas-phase yield measurements indicate that approximately 20% of the SOA of benzene, toluene, and m-xylene could be ascribed to the phenolic route. The SOA densities tend to be initially as high as approximately 1.8 g/cm3 and eventually reach the range of 1.3–1.4 g/cm3. The final SOA density was found to be independent of elemental ratio (O/C) indicating that applying constant density (e.g., 1.4 g/cm3) to SOA formed from different aromatic compounds is a reasonable approximation. Results from a novel on-line PILS-ToF (Particle-into-Liquid Sampler coupled with Agilent Time-of-Flight) are reported. Major signals observed by the on-line/off-line ToF include species consistent with bicyclic hydroperoxides. To the authors' best knowledge, this is the first possible detection of bicyclic hydroperoxides in aromatic SOA.