AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Heterogeneous Reaction Kinetics of Isoprene-Derived Epoxides
THERAN P. RIEDEL, Cassandra Gaston, Sri Hapsari Budisulistiorini, Ying-Hsuan Lin, Zhenfa Zhang, Avram Gold, Joel A. Thornton, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 189 Working Group: Aerosol Chemistry
Abstract Isoprene (2-methyl-,1,3-butadiene) is the most abundant nonmethane hydrocarbon present in the atmosphere and has large potential effects on air quality and radiative forcing. The formation of secondary organic aerosol (SOA) from the photochemical oxidation of isoprene represents a significant source of aerosol loadings, especially in the southeastern United States. Epoxides formed from isoprene oxidation have been shown to be a critical precursor to isoprene-derived SOA. However, the heterogeneous reactions of these epoxides required for subsequent SOA formation remain poorly constrained. We use this as motivation to investigate the heterogeneous kinetics of two isoprene-derived epoxides, methacrylic acid epoxide (MAE) and trans-β-IEPOX (IEPOX) using a glass flow reactor coupled to a chemical ionization mass spectrometer (CIMS) and a scanning electrical mobility sizing system (SEMS). Gas-aerosol reaction probabilities, also called reactive uptake coefficients, are calculated for MAE and IEPOX on 1 - 2 component aerosols under various aerosol compositions and environmental conditions. Compositions and conditions are chosen in order to probe potential chemical drivers of epoxide uptake and put experimental constraints on epoxide-aerosol reaction probabilities that might be encountered in the ambient atmosphere. The obtained reaction probabilities are also incorporated into a simple 0-D, time-dependent box model in order to compare modeled SOA yields with experimental results obtained from chamber studies.