AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Constraining Condensed-Phase Kinetics of Secondary Organic Aerosol Components from Isoprene Epoxydiols
THERAN P. RIEDEL, Kevin Chu, Tianqu Cui, Ying-Hsuan Lin, Sri Hapsari Budisulistiorini, Zhenfa Zhang, Joel A. Thornton, Avram Gold, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 426 Working Group: Aerosol Chemistry
Abstract The formation of epoxide products from isoprene photooxidation is known to be critical precursor of significant secondary organic aerosol (SOA) mass. Isoprene epoxydiols (IEPOX) have been shown to produce substantial amounts of SOA mass and are therefore considered major isoprene-SOA precursors. Heterogeneous reactions of IEPOX on atmospheric aerosols form various aqueous-phase components or “tracers” that contribute to the SOA mass burden. A limited number of the reaction rate constants for these acid-catalyzed aqueous-phase tracer formation reactions have been constrained through bulk laboratory measurements. Namely, only IEPOX tetrol and organosulfate formation have been characterized. While these tracers are responsible for a sizeable fraction of IEPOX-derived SOA, there are a number of other tracer formation reactions have yet to be examined and are of equal importance. To this end we have designed a chemical box model with numerous experimental constraints to explicitly simulate gas- and aqueous-phase reactions during chamber experiments of SOA growth from IEPOX uptake onto acidic sulfate aerosol. Specifically, the model is constrained by recent measurements of the IEPOX reactive uptake coefficient, the few aforementioned experimentally obtained aqueous-phase rate constants, chamber-measured aerosol mass and surface area concentrations, aerosol thermodynamic model calculations, and offline filter measurements of SOA tracer species. Through the use of the offline filter measurements collected during the chamber experiments, we are able to place estimates on the aqueous phase tracer formation rate constants that have yet to be measured for bulk solutions. In this way we obtain valuable constraints on particle-phase species that have been quantified through offline techniques but lack formation rate information.