10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
IEPOX Uptake Changes Particle Morphology and Viscosity
NICOLE OLSON, Ziying Lei, Rebecca Craig, Yue Zhang, Yuzhi Chen, Jason Surratt, Andrew Ault, University of Michigan
Abstract Number: 175 Working Group: Aerosol Chemistry
Abstract In atmospheric particles, organics become mixed with inorganic species via gas-phase oxidation of volatile organic compounds (VOCs) with subsequent condensation of the low-volatility products, such as isoprene epoxydiols (IEPOX), key products of isoprene photo-oxidation, which leads to the formation of secondary organic aerosol (SOA). Chamber and field studies have observed complex physicochemical properties of SOA, such as liquid-liquid phase separations (LLPS) and viscous or glassy organic phases, that inhibit reactive uptake of gaseous species, lower partitioning of chemical species from particle to gas phase, and lower the relative humidity (RH) at which particles undergo efflorescence and deliquescence. To determine the impact these complex morphologies have on the formation of IEPOX-derived SOA, laboratory experiments were conducted by exposing gaseous IEPOX to acidic ammonium sulfate particles coated with α-pinene and toluene SOA at a range of RH (15-50%).To determine individual particle morphology and viscosity, single-particle microscopic and spectroscopic techniques, including scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (SEM-EDX), Raman microspectroscopy, and atomic force microscopy (AFM), were used. After IEPOX uptake, changes to particle morphology and an increase in particle viscosity were observed, which decreased additional IEPOX uptake and limited subsequent particle growth. Particle phase and viscosity determination is necessary to more accurately predict atmospheric fate of ambient aerosols, and the effect aerosols have on heterogeneous (multi-phase) chemistry, climate, and air quality.