Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 9361-9379, 2016
http://www.atmos-chem-phys.net/16/9361/2016/
doi:10.5194/acp-16-9361-2016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
28 Jul 2016
Influence of seed aerosol surface area and oxidation rate on vapor wall deposition and SOA mass yields: a case study with α-pinene ozonolysis
Theodora Nah1, Renee C. McVay2, Xuan Zhang3,a, Christopher M. Boyd1, John H. Seinfeld2,3, and Nga L. Ng1,4 1School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
2Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
3Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA
4School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
anow at: Center for Aerosol and Cloud Chemistry, Aerodyne Research, Billerica, MA, USA
Abstract. Laboratory chambers, invaluable in atmospheric chemistry and aerosol formation studies, are subject to particle and vapor wall deposition, processes that need to be accounted for in order to accurately determine secondary organic aerosol (SOA) mass yields. Although particle wall deposition is reasonably well understood and usually accounted for, vapor wall deposition is less so. The effects of vapor wall deposition on SOA mass yields in chamber experiments can be constrained experimentally by increasing the seed aerosol surface area to promote the preferential condensation of SOA-forming vapors onto seed aerosol. Here, we study the influence of seed aerosol surface area and oxidation rate on SOA formation in α-pinene ozonolysis. The observations are analyzed using a coupled vapor–particle dynamics model to interpret the roles of gas–particle partitioning (quasi-equilibrium vs. kinetically limited SOA growth) and α-pinene oxidation rate in influencing vapor wall deposition. We find that the SOA growth rate and mass yields are independent of seed surface area within the range of seed surface area concentrations used in this study. This behavior arises when the condensation of SOA-forming vapors is dominated by quasi-equilibrium growth. Faster α-pinene oxidation rates and higher SOA mass yields are observed at increasing O3 concentrations for the same initial α-pinene concentration. When the α-pinene oxidation rate increases relative to vapor wall deposition, rapidly produced SOA-forming oxidation products condense more readily onto seed aerosol particles, resulting in higher SOA mass yields. Our results indicate that the extent to which vapor wall deposition affects SOA mass yields depends on the particular volatility organic compound system and can be mitigated through the use of excess oxidant concentrations.

Citation: Nah, T., McVay, R. C., Zhang, X., Boyd, C. M., Seinfeld, J. H., and Ng, N. L.: Influence of seed aerosol surface area and oxidation rate on vapor wall deposition and SOA mass yields: a case study with α-pinene ozonolysis, Atmos. Chem. Phys., 16, 9361-9379, doi:10.5194/acp-16-9361-2016, 2016.
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Short summary
The influence of seed aerosol surface area and oxidation rate on SOA formation in α-pinene ozonolysis is studied. SOA growth rate and mass yields are independent of seed surface area, consistent with the condensation of SOA-forming vapors being dominated by quasi-equilibrium growth. Faster α-pinene oxidation rates and higher SOA mass yields are observed at increasing O3 concentrations, indicating that a faster α-pinene oxidation rate leads to rapidly produced SOA-forming oxidation products.
The influence of seed aerosol surface area and oxidation rate on SOA formation in α-pinene...
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