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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 3
Atmos. Chem. Phys., 14, 1371–1384, 2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Marine trace gases and aerosols over tropical oceans (AMT/ACP...

Atmos. Chem. Phys., 14, 1371–1384, 2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 05 Feb 2014

Research article | 05 Feb 2014

Formation of gas-phase carbonyls from heterogeneous oxidation of polyunsaturated fatty acids at the air–water interface and of the sea surface microlayer

S. Zhou1, L. Gonzalez2, A. Leithead3, Z. Finewax1, R. Thalman2, A. Vlasenko3, S. Vagle4, L.A. Miller4, S.-M. Li3, S. Bureekul5, H. Furutani5, M. Uematsu5, R. Volkamer2, and J. Abbatt1 S. Zhou et al.
  • 1Department of Chemistry, University of Toronto, Toronto, Canada
  • 2Department of Chemistry and Biochemistry and CIRES, University of Colorado, Boulder, Colorado, USA
  • 3Air Quality Research Division, Atmospheric Science and Technology Directorate, Science and Technology Branch, Environment Canada, Canada
  • 4Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney, British Columbia, Canada
  • 5Atmosphere and Ocean Research Institute, University of Tokyo, Chiba, Japan

Abstract. Motivated by the potential for reactive heterogeneous chemistry occurring at the ocean surface, gas-phase products were observed when a reactive sea surface microlayer (SML) component, i.e. the polyunsaturated fatty acids (PUFA) linoleic acid (LA), was exposed to gas-phase ozone at the air–seawater interface. Similar oxidation experiments were conducted with SML samples collected from two different oceanic locations, in the eastern equatorial Pacific Ocean and from the west coast of Canada. Online proton-transfer-reaction mass spectrometry (PTR-MS) University of Colorado light-emitting diode cavity-enhanced differential optical absorption spectroscopy (LED-CE-DOAS) were used to detect oxygenated gas-phase products from the ozonolysis reactions. The LA studies indicate that oxidation of a PUFA monolayer on seawater gives rise to prompt and efficient formation of gas-phase aldehydes. The products are formed via the decomposition of primary ozonides which form upon the initial reaction of ozone with the carbon–carbon double bonds in the PUFA molecules. In addition, two highly reactive dicarbonyls, malondialdehyde (MDA) and glyoxal, were also generated, likely as secondary products. Specific yields relative to reactant loss were 78%, 29%, 4% and < 1% for n-hexanal, 3-nonenal, MDA and glyoxal, respectively, where the yields for MDA and glyoxal are likely lower limits. Heterogeneous oxidation of SML samples confirm for the first time that similar carbonyl products are formed via ozonolysis of environmental samples.

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