The effects of aging processes on critical supersaturation ratios of ultrafine carbon aerosols

R. Kotzick, R. Niessner

Research output: Contribution to journalConference articlepeer-review

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The condensation properties of polydisperse aged ultrafine carbon aerosols (particle diameter < 1 μm) have been investigated by means of a variable supersaturation condensation nucleus counter. The critical supersaturation (S(c)), as the point, where 50% of all particles have been activated and grew to droplets was compared to the median dry particle diameter for pure carbon aerosols, benzo[a]pyrene-tagged carbon aerosols and external mixtures of the carbon particles with sodium chloride and sulphuric acid aerosols. Additionally, ozone as oxidising gaseous compound was added in some of the experiments. Simple coagulation of pure and benzo[a]pyrene- tagged carbon particles resulted in only slightly lower values for S(c) due to the increased median particle diameter. The formation of soluble functionalities on the particle surface, i.e. the coagulation with the soluble sodium chloride and sulphuric acid aerosols or the chemical decomposition of benzo[a]pyrene into polar, hydrophilic products due to the reaction with ozone resulted in significant lower values for S(c) for the modified carbon aerosol. The necessary supersaturations for the increased hydrophilic particles dropped to atmospherically relevant values of 3% after 5 h reaction time (benzo[a]pyrene decomposition) and 15 h (coagulation with soluble particles), respectively.

Original languageEnglish
Pages (from-to)2669-2677
Number of pages9
JournalAtmospheric Environment
Issue number17
StatePublished - Aug 1999
EventProceedings of the 1997 6th International Conference on Carbonaceous Particles in the Atmosphere - Vienna, Austria
Duration: 22 Sep 199724 Sep 1997


  • Benzo[a]pyrene
  • Carbon aerosol
  • Coagulation
  • Condensation properties
  • Critical supersaturation
  • Ozone
  • Sodium chloride
  • Sulphuric acid


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