AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Density and Elemental Ratios of Secondary Organic Aerosol: Application of a Density Prediction Method
SHUNSUKE NAKAO, Ping Tang, Xiaochen Tang, Christopher Clark, Li Qi, Eric Seo, Chia-Li Chen, Akua Asa-Awuku, David R. Cocker III, University of California, Riverside
Abstract Number: 129 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract This study investigates density and elemental ratios of secondary organic aerosol (SOA) formed by the oxidation of 23 different volatile organic compounds with a wide range of molecular size (C5~C15) in an environmental chamber. Differences in oxidation conditions (in terms of VOC:NOx, H2O2, and O3) did not significantly effect SOA density. Reactants with a larger number of carbons (C14~15) yielded SOA with lower density (1.06~1.20 g/cm3) compared with smaller ones (e.g., phenol SOA: 1.42 g/cm3) consistent with different extents of oxidation of the parent molecule. A recent study proposed a semi-empirical relationship between elemental ratios (O/C and H/C) and organic material density (Kuwata et al., 2011). The prediction method therein is evaluated against the large experimental data set of this study acquired in the UC Riverside/CE-CERT environmental chamber. The predicted particle densities agree with experimental measurements within 20% for more than 90% of the experiments. The effects of nitrogen and sulfur on the density prediction remain unclear.