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Published July 16, 2013 | Supplemental Material + Published
Journal Article Open

Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation


Organic aerosols are ubiquitous in the atmosphere and play a central role in climate, air quality, and public health. The aerosol size distribution is key in determining its optical properties and cloud condensation nucleus activity. The dominant portion of organic aerosol is formed through gas-phase oxidation of volatile organic compounds, so-called secondary organic aerosols (SOAs). Typical experimental measurements of SOA formation include total SOA mass and atomic oxygen-to-carbon ratio. These measurements, alone, are generally insufficient to reveal the extent to which condensed-phase reactions occur in conjunction with the multigeneration gas-phase photooxidation. Combining laboratory chamber experiments and kinetic gas-particle modeling for the dodecane SOA system, here we show that the presence of particle-phase chemistry is reflected in the evolution of the SOA size distribution as well as its mass concentration. Particle-phase reactions are predicted to occur mainly at the particle surface, and the reaction products contribute more than half of the SOA mass. Chamber photooxidation with a midexperiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. Although experiments need to be conducted with other SOA precursor hydrocarbons, current results demonstrate coupling between particle-phase chemistry and size distribution dynamics in the formation of SOAs, thereby opening up an avenue for analysis of the SOA formation process.

Additional Information

© 2013 National Academy of Sciences. Edited by Mark H. Thiemens, University of California at San Diego, La Jolla, CA, and approved June 13, 2013 (received for review April 21, 2013). Published online before print July 1, 2013. We thank Xuan Zhang and Matt Coggon for assistance in the experiments. This work was supported by US Department of Energy Grant DE-SC0006626 and National Science Foundation Grant AGS-1057183. M.S. is supported by a Japan Society for the Promotion of Science Postdoctoral Fellowship for Research Abroad. Author contributions: M.S., L.D.Y., and J.H.S. designed research; M.S., L.D.Y., K.A.S., C.L.L., and J.S.C. performed research; M.S., L.D.Y., K.A.S., C.L.L., J.S.C., A.Z., and P.J.Z. analyzed data; M.S., L.D.Y., K.A.S., and C.L.L. wrote the supplement; and M.S., and J.H.S. wrote the paper.

Attached Files

Published - PNAS-2013-Shiraiwa-11746-50.pdf

Supplemental Material - pnas.201307501SI.pdf


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