Atmos. Chem. Phys. Discuss., 10, 863-883, 2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Temperature effect on physical and chemical properties of secondary organic aerosol from m-xylene photooxidation
L. Qi, S. Nakao, P. Tang, and D. R. Cocker III
Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, CA 92521, USA
College of Engineering, Center for Environmental Research and Technology (CE-CERT), 1084 Columbia Avenue, Riverside, CA 92507, USA

Abstract. The chemical and physical differences of secondary organic aerosol (SOA) formed at select isothermal temperatures (278 K, 300 K, and 313 K) are explored with respect to density, particle volatility, particle hygroscopicity, and elemental chemical composition. A transition point in SOA density, volatility, hygroscopicity and elemental composition is observed near 290–292 K as SOA within an environmental chamber is heated from 278 K to 313 K, indicating the presence of a thermally labile compound. No such transition points are observed for SOA produced at 313 K or 300 K and subsequently cooled to 278 K. The SOA formed at the lowest temperatures (278 K) is more than double the SOA formed at 313 K. SOA formed at 278 K is less hydrophilic and oxygenated while more volatile and dense than SOA formed at 300 K or 313 K. The properties of SOA formed at 300 K and 313 K when reduced to 278 K did not match the properties of SOA initially formed at 278 K. This study demonstrates that it is insufficient to utilize the enthalpy of vaporization when predicting SOA temperature dependence.

Citation: Qi, L., Nakao, S., Tang, P., and Cocker III, D. R.: Temperature effect on physical and chemical properties of secondary organic aerosol from m-xylene photooxidation, Atmos. Chem. Phys. Discuss., 10, 863-883, doi:10.5194/acpd-10-863-2010, 2010.
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