AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
SOA Aging and Oligomer Content and their Effect on Volatility and Viscosity of SOA Particles Generated from Different Precursors
JACQUELINE WILSON, Alla Zelenyuk, Dan Imre, Josef Beranek, Pacific Northwest National Laboratory
Abstract Number: 428 Working Group: Aerosol Chemistry
Abstract Formation, properties, transformations and temporal evolution of secondary organic aerosol (SOA) particles strongly depend on particle phase and volatility. Our recent studies indicate that laboratory-generated alpha-pinene SOA particles are highly viscous semi-solids with viscosity characteristic of tars, and their evaporation rates are orders of magnitude slower than previously assumed.
Moreover, numerous recent studies provide evidence that SOA particles contain significant amounts of high molecular weight organic compounds (oligomers), which affect SOA volatility and have the potential to severely retard diffusion, mixing, and thus evaporation of smaller molecules. We have shown that when SOA particles are made in the presence of vapors of semi-volatile hydrophobic compounds, such molecules become incorporated and trapped within the SOA and their subsequent evaporation rates and thus their rates of diffusion through the SOA and SOA viscosity can be obtained.
Here we present the results of recent studies that explore the relationship between SOA oligomer content and SOA volatility and viscosity. These studies include SOA particles generated by oxidation of several different precursors, including alpha-pinene, isoprene, limonene, n-alkenes, and cyclo-alkenes.
We, and others, also find that oligomer content in SOA increases with time, and with it we expect corresponding changes in viscosity and volatility. We will present the results of studies aimed at characterizing evaporation kinetics and viscosity of SOA particles as a function of particle age. We will also present our findings on the effect of hydrophobic organics on SOA oligomer content, its volatility, and viscosity.