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Published June 18, 2013 | public
Journal Article

On the Mixing and Evaporation of Secondary Organic Aerosol Components


The physical state and chemical composition of an organic aerosol affect its degree of mixing and its interactions with condensing species. We present here a laboratory chamber procedure for studying the effect of the mixing of organic aerosol components on particle evaporation. The procedure is applied to the formation of secondary organic aerosol (SOA) from α-pinene and toluene photooxidation. SOA evaporation is induced by heating the chamber aerosol from room temperature (25 °C) to 42 °C over 7 h and detected by a shift in the peak diameter of the SOA size distribution. With this protocol, α-pinene SOA is found to be more volatile than toluene SOA. When SOA is formed from the two precursors sequentially, the evaporation behavior of the SOA most closely resembles that of SOA from the second parent hydrocarbon, suggesting that the structure of the mixed SOA resembles a core of SOA from the initial precursor coated by a layer of SOA from the second precursor. Such a core-and-shell configuration of the organic aerosol phases implies limited mixing of the SOA from the two precursors on the time scale of the experiments, consistent with a high viscosity of at least one of the phases.

Additional Information

© 2013 American Chemical Society. Received: March 4, 2013; Revised: May 15, 2013; Accepted: May 20, 2013; Published: May 31, 2013. This work was supported by the Office of Science (Biological and Environmental Research), US Department of Energy Grant DE-SC 0006626. We thank Jill Craven, Rebecca Schwantes, Lindsay Yee, and Xuan Zhang for experimental assistance, Andrew Metcalf and Manabu Shiraiwa for helpful discussions, and Yu Jun Leong and Robert Griffin for lending us their AMS power supply.

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