AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
SOA Formation from Photooxidation of Naphthalene and Methylnaphthalenes with m-Xylene and Surrogate Mixtures
Chia-Li Chen, Lijie Li, DAVID R. COCKER III, University of California, Riverside
Abstract Number: 325 Working Group: Aerosol Chemistry
Abstract SOA from photooxidation of individual PAHs such as naphthalene, 1-methylnaphthalene, 2-methylnaphthalene and mixed with m-xylene or an atmospheric surrogate mixture under low NO$_x condition and extremely low NO$_x (H$_2O$_2) was explored in the UCR CE-CERT environmental chamber. Different mixing ratios between PAHs and m-xylene (PAHs (ppb): m-xylene (ppb) = 1.5:1 ~1:1:4) indicate that the addition of m-xylene to PAH photooxidation experiments suppressed SOA formation from the PAH precursor. The SOA growth rate relationship of aerosol mass concentration (∆M$_0) versus hydrocarbon reacted (∆HC) from different PAHs-m-xylene mixture is correlated with initial m-xylene/NO, PAHs/NO, [OH]/[HO$_2] ratio, [NO]/[HO$_2] ratio and [HO$_2]/[RO$_2] ratio. It is observed that higher m-xylene/PAHs ratios and higher initial m-xylene/NO ratios lead to less net SOA formation. The chemical composition characteristics such as f44 versus f43, H/C ratio, O/C ratio, and the oxidation state of the carbon (OS$_c) showed that PAHs-m-xylene SOA continuously ages and the SOA exhibits characteristics of both individual precursors. The atmospheric surrogate mixture chosen for the surrogate/PAH mixtures was based on the surrogate used to develop the Carter O$_3 reactivity scales. Our results showed that the surrogate mixture photooxidation also suppressed SOA formation from PAHs by influencing gas-phase chemical reactivity.