AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Photooxidation of Isoprene Epoxydiol (IEPOX)-Derived Secondary Organic Aerosol
KELVIN BATES, Tran Nguyen, Rebecca Schwantes, Xuan Zhang, Matthew Coggon, Richard Flagan, Brian Stoltz, Paul Wennberg, John Seinfeld, Caltech
Abstract Number: 390 Working Group: Aerosol Chemistry
Abstract Isoprene epoxydiol (IEPOX), a second-generation oxidation product of isoprene, has recently been identified as a key intermediate in the formation of secondary organic aerosol (SOA) from isoprene under low-NO conditions. Following its reactive uptake onto particles, IEPOX is typically converted to 2-methyltetrols or organosulfates by acid- or ammonium-catalyzed mechanisms. These low-volatility products are generally expected to remain in the particle phase, though their subsequent chemistry has not yet been explored. Using synthetic IEPOX and various inorganic seed particles, we have performed environmental chamber experiments to investigate the fate of IEPOX-derived SOA under exposure to photooxidation by OH radicals. Particle mass concentration and chemical composition were monitored by aerosol mass spectrometry, scanning mobility particle sizing, and liquid chromatography-mass spectrometry of filter samples, while concentrations of gas phase compounds were measured by CF$_3O$^(-) chemical ionization mass spectrometry. We will present results showing changes in both gas and particle phase composition during photooxidation, including their dependence on both seed particle composition and OH concentration. Preliminary data show that the photochemical loss of IEPOX-derived SOA mass may be an important consideration for predicting aerosol loading and gas phase oxidative chemistry in isoprene-rich environments.