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Formation and evolution of molecular products in α-pinene secondary organic aerosol

Zhang, Xuan and McVay, Renee C. and Huang, Dan D. and Dalleska, Nathan F. and Aumont, Bernard and Flagan, Richard C. and Seinfeld, John H. (2015) Formation and evolution of molecular products in α-pinene secondary organic aerosol. Proceedings of the National Academy of Sciences of the United States of America, 112 (46). pp. 14168-14173. ISSN 0027-8424. PMCID PMC4655512. doi:10.1073/pnas.1517742112.

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Much of our understanding of atmospheric secondary organic aerosol (SOA) formation from volatile organic compounds derives from laboratory chamber measurements, including mass yield and elemental composition. These measurements alone are insufficient to identify the chemical mechanisms of SOA production. We present here a comprehensive dataset on the molecular identity, abundance, and kinetics of α-pinene SOA, a canonical system that has received much attention owing to its importance as an organic aerosol source in the pristine atmosphere. Identified organic species account for ∼58–72% of the α-pinene SOA mass, and are characterized as semivolatile/low-volatility monomers and extremely low volatility dimers, which exhibit comparable oxidation states yet different functionalities. Features of the α-pinene SOA formation process are revealed for the first time, to our knowledge, from the dynamics of individual particle-phase components. Although monomeric products dominate the overall aerosol mass, rapid production of dimers plays a key role in initiating particle growth. Continuous production of monomers is observed after the parent α-pinene is consumed, which cannot be explained solely by gas-phase photochemical production. Additionally, distinct responses of monomers and dimers to α-pinene oxidation by ozone vs. hydroxyl radicals, temperature, and relative humidity are observed. Gas-phase radical combination reactions together with condensed phase rearrangement of labile molecules potentially explain the newly characterized SOA features, thereby opening up further avenues for understanding formation and evolution mechanisms of α-pinene SOA.

Item Type:Article
Related URLs:
URLURL TypeDescription Information CentralArticle
Zhang, Xuan0000-0002-7203-2293
McVay, Renee C.0000-0001-7766-5009
Dalleska, Nathan F.0000-0002-2059-1587
Aumont, Bernard0000-0002-2781-0877
Flagan, Richard C.0000-0001-5690-770X
Seinfeld, John H.0000-0003-1344-4068
Additional Information:© 2015 National Academy of Sciences. Contributed by John H. Seinfeld, September 30, 2015 (sent for review September 4, 2015; reviewed by Thorsten Hoffmann and Murray V. Johnston). Published online before print November 2, 2015. We thank John Crounse and Paul Wennberg for useful discussions. This work was supported by National Science Foundation Grant AGS-1523500. Author contributions: X.Z., R.C.F., and J.H.S. designed research; X.Z., D.D.H., and N.F.D. performed research; X.Z., R.C.M., and B.A. analyzed data; and X.Z. and J.H.S. wrote the paper. Reviewers: T.H., Johannes Gutenberg University; and M.V.J., University of Delaware. The authors declare no conflict of interest. This article contains supporting information online at
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Subject Keywords:secondary organic aerosol; particulate matter; air quality; climate
Issue or Number:46
PubMed Central ID:PMC4655512
Record Number:CaltechAUTHORS:20151109-082447673
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Official Citation:Xuan Zhang, Renee C. McVay, Dan D. Huang, Nathan F. Dalleska, Bernard Aumont, Richard C. Flagan, and John H. Seinfeld Formation and evolution of molecular products in α-pinene secondary organic aerosol PNAS 2015 112 (46) 14168-14173; published ahead of print November 2, 2015, doi:10.1073/pnas.1517742112
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:61971
Deposited By: Tony Diaz
Deposited On:09 Nov 2015 18:21
Last Modified:17 May 2022 17:10

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