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Open Access Publications from the University of California

Physical properties of ambient and laboratorygenerated secondary organic aerosol

  • Author(s): O'Brien, RE
  • Neu, A
  • Epstein, SA
  • MacMillan, AC
  • Wang, B
  • Kelly, ST
  • Nizkorodov, SA
  • Laskin, A
  • Moffet, RC
  • Gilles, MK
  • et al.

© 2014. American Geophysical Union. All Rights Reserved. The size and thickness of organic aerosol particles collected by impaction in five field campaigns were compared to those of laboratory-generated secondary organic aerosols (SOA). Scanning transmission X-ray microscopy was used to measure the total carbon absorbance (TCA) by individual particles as a function of their projection areas on the substrate. Particles with higher viscosity/surface tension can be identified by a steeper slope on a plot of TCA versus size because they flatten less upon impaction. The slopes of the ambient data are statistically similar indicating a small range of average viscosities/surface tensions across five field campaigns. Steeper slopes were observed for the plots corresponding to ambient particles, while smaller slopes were indicative of the laboratory-generated SOA. This comparison indicates that ambient organic particles have higher viscosities/surface tensions than those typically generated in laboratory SOA studies.

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