Articles | Volume 11, issue 20
Research article
27 Oct 2011
Research article |  | 27 Oct 2011

Secondary organic aerosol formation from phenolic compounds in the absence of NOx

S. Nakao, C. Clark, P. Tang, K. Sato, and D. Cocker III

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 under low NOx conditions. The SOA densities tend to be initially as high as approximately 1.8 g cm−3 and eventually reach the range of 1.3–1.4 g cm−3. The final SOA density was found to be independent of elemental ratio (O/C) indicating that applying constant density (e.g., 1.4 g cm−3) to SOA formed from different aromatic compounds tested in this study is a reasonable approximation. Results from a novel on-line PILS-TOFMS (Particle-into-Liquid Sampler coupled with Agilent Time-of-Flight Mass Spectrometer) are reported. Major signals observed by the on-line/off-line Agilent TOFMS indicated that products had the same number of carbon atoms as their parent aromatics, suggesting importance of ring-retaining products or ring-opening products following ring-cleavage.

Final-revised paper