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Volume 16, issue 11
Atmos. Chem. Phys., 16, 6721–6733, 2016
https://doi.org/10.5194/acp-16-6721-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 16, 6721–6733, 2016
https://doi.org/10.5194/acp-16-6721-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 03 Jun 2016

Research article | 03 Jun 2016

Substantial secondary organic aerosol formation in a coniferous forest: observations of both day- and nighttime chemistry

Alex K. Y. Lee1, Jonathan P. D. Abbatt1, W. Richard Leaitch2, Shao-Meng Li2, Steve J. Sjostedt1,a, Jeremy J. B. Wentzell2, John Liggio2, and Anne Marie Macdonald2 Alex K. Y. Lee et al.
  • 1Department of Chemistry, University of Toronto, Toronto, Canada
  • 2Science and Technology Branch, Environment Canada, Downsview, Canada
  • anow at: NOAA ESRL Chemical Sciences Division, Boulder, USA

Abstract. Substantial biogenic secondary organic aerosol (BSOA) formation was investigated in a coniferous forest mountain region in Whistler, British Columbia. A largely biogenic aerosol growth episode was observed, providing a unique opportunity to investigate BSOA formation chemistry in a forested environment with limited influence from anthropogenic emissions. Positive matrix factorization of aerosol mass spectrometry (AMS) measurement identified two types of BSOA (BSOA-1 and BSOA-2), which were primarily generated by gas-phase oxidation of monoterpenes and perhaps sesquiterpenes. The temporal variations of BSOA-1 and BSOA-2 can be explained by gas–particle partitioning in response to ambient temperature and the relative importance of different oxidation mechanisms between day and night. While BSOA-1 arises from gas-phase ozonolysis and nitrate radical chemistry at night, BSOA-2 is likely less volatile than BSOA-1 and consists of products formed via gas-phase oxidation by OH radical and ozone during the day. Organic nitrates produced through nitrate radical chemistry can account for 22–33 % of BSOA-1 mass at night. The mass spectra of BSOA-1 and BSOA-2 have higher values of the mass fraction of m/z 91 (f91) compared to the background organic aerosol. Using f91 to evaluate BSOA formation pathways in this unpolluted, forested region, heterogeneous oxidation of BSOA-1 is a minor production pathway of BSOA-2.

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Substantial biogenic secondary organic aerosol (BSOA) formation was investigated in a coniferous forest mountain region in Whistler, British Columbia. A largely biogenic aerosol growth episode was observed, providing a unique opportunity to investigate BSOA formation chemistry in a forested environment. In particular, our observations provide insights into the relative importance of different oxidation mechanisms between day and night.
Substantial biogenic secondary organic aerosol (BSOA) formation was investigated in a coniferous...
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