HR: 0800h
AN: A21C-0751    [Abstracts]
TI: Cloud Condensation Nucleus (CCN) Activation Properties of Biogenic Secondary Organic Aerosol
AU: * VanReken, T M
EM: vanreken@caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd. M/C 210-41, Pasadena, CA 91125 United States
AU: Ng, N L
EM: ng@caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd. M/C 210-41, Pasadena, CA 91125 United States
AU: Flagan, R C
EM: flagan@caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd. M/C 210-41, Pasadena, CA 91125 United States
AU: Seinfeld, J H
EM: seinfeld@caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd. M/C 210-41, Pasadena, CA 91125 United States
AB: Organic compounds are known to comprise a significant fraction of the atmospheric aerosol population and have been found to contribute to the concentration of cloud condensation nuclei (CCN). Much of this organic material is secondary in nature; secondary organic aerosol (SOA) is formed when volatile organic compounds are oxidized to form less volatile products, which then condense into the aerosol phase. Many organic compounds found in the atmosphere, of both anthropogenic and biogenic origin, have been found to produce SOA. Such reactions typically result in complex mixtures of products, only a fraction of which have been identified. Thus while there have been several studies exploring the potential for organic particles to act as CCN (including some of the compounds identified in SOA products), there have been almost no direct investigation of the potential CCN activity of SOA. This paper presents the results of a series of experiments measuring directly the CCN activity of SOA produced by the ozonolysis of several common biogenic compounds. Six compounds were studied: five monoterpenes ($\alpha$-pinene, $\beta$-pinene, $\Delta^{3}$-carene, limonene, terpinolene) and one terpinoid alcohol (terpinen-4-ol). The chosen monoterpenes represent an estimated 87% of global monoterpene emissions, while the terpenoid alcohols make up approximately 25% of the other biogenic compounds capable of forming SOA. In each experiment, SOA was generated under controlled conditions at the Caltech indoor facility. Over several hours, CCN concentrations were measured at supersaturations ranging from 0.27% to 0.80%. These data are compared to simultaneous particle concentration and size distribution observations to determine the relationship between particle diameter and CCN activity. The analysis indicates considerable variation in CCN activity among the experiments; possible causes for such variability are explored.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting