Insights into the Formation and Evolution of Individual Compounds in the Particulate Phase during Aromatic Photo-Oxidation

Research output: Contribution to journalArticlepeer-review


  • Kelly L. Pereira
  • Jacqueline F. Hamilton
  • Andrew R. Rickard
  • Martyn W. Ward
  • Kevin P. Wyche
  • Amalia Muñoz
  • Teresa Vera
  • Mónica Vázquez
  • Esther Borrás
  • Milagros Ródenas

Colleges, School and Institutes


Secondary organic aerosol (SOA) is well-known to have adverse effects on air quality and human health. However, the dynamic mechanisms occurring during SOA formation and evolution are poorly understood. The time-resolved SOA composition formed during the photo-oxidation of three aromatic compounds, methyl chavicol, toluene and 4-methyl catechol, were investigated at the European Photoreactor. SOA was collected using a particle into liquid sampler and analyzed offline using state-of-the-art mass spectrometry to produce temporal profiles of individual photo-oxidation products. In the photo-oxidation of methyl chavicol, 70 individual compounds were characterized and three distinctive temporal profile shapes were observed. The calculated mass fraction (Ci,aer/COA) of the individual SOA compounds showed either a linear trend (increasing/decreasing) or exponential decay with time. Substituted nitrophenols showed an exponential decay, with the nitro-group on the aromatic ring found to control the formation and loss of these species in the aerosol phase. Nitrophenols from both methyl chavicol and toluene photo-oxidation experiments showed a strong relationship with the NO2/NO (ppbv/ppbv) ratio and were observed during initial SOA growth. The location of the nitrophenol aromatic substitutions was found to be critically important, with the nitrophenol in the photo-oxidation of 4-methyl catechol not partitioning into the aerosol phase until irradiation had stopped; highlighting the importance of studying SOA formation and evolution at a molecular level.

Bibliographic note

doi: 10.1021/acs.est.5b03377


Original languageEnglish
Pages (from-to)13168-13178
Number of pages11
JournalEnvironmental Science & Technology
Issue number22
Early online date16 Oct 2015
Publication statusPublished - 17 Nov 2015