AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
The Effects of Aerosol Phase State on Secondary Organic Aerosol Formation from the Acid-Catalyzed Reactive Uptake of Isoprene-Derived Epoxydiols
YUE ZHANG, Yuzhi Chen, Andrew Lambe, Amy Bondy, Nicole Olson, Rebecca Craig, Zhenfa Zhang, Avram Gold, Timothy Onasch, John Jayne, Douglas Worsnop, Charles Kolb, William Vizuete, Andrew Ault, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 389 Working Group: Aerosol Chemistry
Abstract Acid-catalyzed multiphase reactions between gas- and particle-phase constituents are an important formation mechanism for atmospheric secondary organic aerosol (SOA). Aerosol phase state is thought to influence the reactive uptake process of gas phase precursors, especially when the diffusion rate of gas species inside the particles is limited due to high particle viscosity. However, there is little experimental evidence to show the dependence of reactive uptake processes on particle phase state. This laboratory study systematically examines the reactive uptake probability of isoprene-derived epoxydiols (IEPOX) onto acidic sulfate particles with various types of pre-existing SOA coatings. The reactive uptake probability is obtained as a function of SOA composition, oxidation state, coating thickness, and relative humidity (RH). Results show that certain types of pre-existing SOA coatings may significantly reduce IEPOX reactive uptake probability, in some cases by nearly an order of magnitude, especially under low RH conditions. The diffusion coefficient of IEPOX in the particle phase is also derived by varying the coating thickness of SOA layers at different RHs, which could be expanded to similar gas-phase species that only form aerosol by reactive uptake processes. These results can be used in order to accurately characterize the formation and evolution of IEPOX-derived SOA. Moreover, the approach used in this study could be more widely applied to other multiphase chemical systems in regional and global scale models to better predict the impact of SOA on climate, human health, and visibility.