Gas phase precursors to anthropogenic secondary organic aerosol: detailed observations of 1,3,5-trimethylbenzene photooxidation
Atmospheric Chemistry and Physics
A series of photooxidation experiments were conducted in an atmospheric simulation chamber in order to investigate the oxidation mechanism and secondary organic aerosol (SOA) formation potential of the model anthropogenic gas phase precursor, 1,3,5-trimethylbenzene. Alongside specific aerosol measurements, comprehensive gas phase measurements, primarily by Chemical Ionisation Reaction Time-of-Flight Mass Spectrometry (CIR-TOF-MS), were carried out to provide detailed insight into the
... and behaviour of the organic components of the gas phase matrix during SOA formation. An array of gas phase organic compounds was measured during the oxidation process, including several previously unmeasured primary bicyclic compounds possessing various functional groups. Analysis of results obtained during this study implies that these peroxide bicyclic species along with a series of ring opening products and organic acids contribute to SOA growth. The effect of varying the VOC/NO x ratio on SOA formation was explored, as was the effect of acid seeding. It was found that low NO x conditions favour more rapid aerosol formation and a higher aerosol yield, a result that implies a role for organic peroxides in the nucleation process and SOA growth. It has been established that SOA mass constitutes a major fraction of the total atmospheric loading of organic aerosol and indeed the more general class of atmospheric particulate matter, on both the local and the global (Kanakidou et al., 2005) scale. Under certain scenarios atmospheric SOA can comprise as much as 90% of organic aerosol mass and 50% of the total mass of atmospheric aerosol .