AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Influences of SO2 and NH3 Levels on Ambient Isoprene Epoxydiol (IEPOX)-Derived SOA Formation in the Rural Southeastern United States
YING-HSUAN LIN, Eladio Knipping, Eric Edgerton, Stephanie Shaw, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 590 Working Group: Remote and Regional Atmospheric Aerosols
Abstract Recent work through organic synthesis and controlled chamber studies has confirmed that reactive uptake of gaseous isoprene epoxydiols (IEPOX) are key intermediates in the formation of isoprene-derived SOA constituents under low-NOx conditions (Lin et al., 2012). Heterogeneous oxirane ring-opening reactions of IEPOX have also been reported to be atmospherically relevant under typical tropospheric conditions, with reaction rates enhanced by aerosol acidity. In the present study, ambient fine aerosol (PM2.5) samples were collected and analyzed to investigate the effects of aerosol acidity on isoprene SOA formation in the rural atmosphere influenced by anthropogenic sulfur dioxide (SO2) and ammonia (NH3) emissions. Filter samples were collected from Yorkville, GA, a rural site with high isoprene emissions located in the Southeastern Aerosol Research and Characterization Study (SEARCH) network during the summer of 2010. Conditional sampling strategies were employed to collect aerosol samples under pre-defined environmental thresholds (i.e., high vs. low SO2/NH3 conditions) to distinguish the influences of different ambient SO2 and NH3 levels on isoprene SOA formation. IEPOX-derived SOA constituents, including 3-methyltetrahydrofuran-3,4-diols, 2-methyltetrols, C5-alkene triols, dimers, as well as their organosulfate derivatives, are chemically characterized and quantified by advanced off-line analytical techniques (i.e., UPLC/ESI-HR-Q-TOFMS, GC/MS). In situ aerosol pH is estimated by aerosol thermodynamic models (i.e., E-AIM models). Important results regarding correlations between SOA constituents and aerosol acidities, as well as available complementary chemical and meteorological measurements will be presented in order to help provide insights into the atmospheric formation of IEPOX-derived SOA.
Reference:
Lin, Y.-H.; Zhang, Z.; Docherty, K. S.; Zhang, H.; Budisulistiorini, S. H.; Rubitschun, C. L.; Shaw, S. L.; Knipping, E. M.; Edgerton, E. S.; Kleindienst, T. E.; Gold, A.; Surratt, J. D., Isoprene epoxydiols as precursors to secondary organic aerosol formation: Acid-catalyzed reactive uptake studies with authentic compounds. Environ. Sci. Technol. 2012, 46 (1), 250-258.