Abstract View
Viscosity of Secondary Organic Aerosol: Effects of Composition and Oxidation Method
GIUSEPPE CRESCENZO, Vahe Baboomian, Natalie R. Smith, Sergey Nizkorodov, Allan Bertram, University of British Columbia
Abstract Number: 29
Working Group: Aerosols, Clouds and Climate
Abstract
Forests emit large quantities of volatile organic compounds (VOC) into the troposphere. Upon oxidation, lower volatility products condense and form secondary organic aerosol (SOA). SOA constitutes a large mass fraction of submicron atmospheric aerosols. SOA is important for air quality and influences climate. Information on the viscosity of SOA is needed to predict their role in air quality and climate. For example, the viscosity of SOA can impact the growth and evaporation rate of SOA, their ability to act as ice nucleating particles, and their ability to transport pollutants over long distances. Nevertheless, the viscosity of SOA remains uncertain. Here we report viscosities as a function of relative humidity for SOA derived from terpene and sesquiterpene photooxidation and dark ozonolysis. From the measured viscosities and the Stokes-Einstein equation, we determined diffusion coefficients and mixing times of organic molecules within the SOA. We show that particle viscosity and mixing times within the SOA depends strongly on the oxidation method and the type of VOC used to generate the SOA. Photooxidation lead to higher viscosities compared to dark ozonolysis, and a complex mixture of VOCs resulted in a higher SOA viscosity compared to SOA generated from α-pinene alone.