Distribution of gaseous and particulate organic composition during dark α-pinene ozonolysis - Discussion Paper

Marie Camredon, Jaqui Hamilton, Mohammed Alam, Kevin Wyche, Timo Carr, Iain White, Paul Monks, Andrew Rickard, William Bloss

Research output: Contribution to journalArticlepeer-review


Secondary organic aerosol (SOA) affects atmospheric composition, air quality and radiative transfer. However major difficulties are encountered in the development of reliable models for SOA formation. Constraints on processes involved in SOA formation can be obtained by interpreting the speciation and evolution of organics in the gaseous and condensed phase simultaneously. In this study we investigate SOA formation from dark α-pinene ozonolysis with particular emphasis upon the mass distribution of gaseous and particulate organic species. A detailed model for SOA formation is compared with the results from experiments performed in the EUropean PHOtoREactor (EUPHORE) simulation chamber, including on-line gas-phase composition obtained from Chemical-Ionization-Reaction Time-Of-Flight Mass-Spectrometry measurements, and off-line analysis of SOA samples performed by Electrospray Ionisation Ion Trap Mass Spectrometry. The temporal profile of SOA mass concentration is relatively well reproduced by the model. Sensitivity analysis highlights the importance of the choice of vapour pressure estimation method. Comparisons of the simulated gaseous and condensed-phase mass distributions with those observed show a generally good agreement. The simulated speciation has been used to (i) propose a chemical structure for the principal gaseous semi-volatile organic compounds and condensed monomer organic species and (ii) explore the possible contribution of a range of accretion reactions occurring in the condensed phase. We find that oligomer formation through esterification reactions gives the best agreement between the observed and simulated mass spectra
Original languageEnglish
Pages (from-to)27837-27892
Number of pages56
JournalAtmospheric Chemistry and Physics Discussions
Publication statusPublished - 23 Dec 2009


  • alpha-pinene
  • ozonolysis
  • atmospheric science
  • secondary organic aerosol
  • volatile organic compound


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