Sub-23 nm Particles Dominate Non-Volatile Particle Number Emissions of Road Traffic

Henna Lintusaari, Heino Kuuluvainen, Joonas Vanhanen, Laura Salo, Harri Portin, Anssi Järvinen, Paxton Juuti, Riina Hietikko, Kimmo Teinilä, Hilkka Timonen, Jarkko V. Niemi, Topi Rönkkö

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Ultrafine particles (<100 nm) in urban air are a serious health hazard not yet fully understood. Therefore, particle number concentration monitoring was recently included in the WHO air quality guidelines. At present, e.g., the EU regulates particle number only regarding the emissions of solid particles larger than 23 nm emitted by vehicles. The aim of this study was to examine the non-volatile fraction of sub-23 nm particles in a traffic-influenced urban environment. We measured the number concentration of particles larger than 1.4, 3, 10, and 23 nm in May 2018. Volatile compounds were thermally removed in the sampling line and the line losses were carefully determined. According to our results, the sub-23 nm particles dominated the non-volatile number concentrations. Additionally, based on the determined particle number emission factors, the traffic emissions of non-volatile sub-10 nm particles can be even 3 times higher than those of particles larger than 10 nm. Yet, only a fraction of urban sub-10 nm particles consisted of non-volatiles. Thus, while the results highlight the role of ultrafine particles in the traffic-influenced urban air, a careful consideration is needed in terms of future particle number standards to cover the varying factors affecting measured concentrations.

Original languageEnglish
Pages (from-to)10763-10772
Number of pages10
JournalEnvironmental Science and Technology
Issue number29
Publication statusPublished - 2023
Publication typeA1 Journal article-refereed


  • air quality
  • emission factor
  • nanoparticle
  • street canyon
  • ultrafine particle
  • urban pollution

Publication forum classification

  • Publication forum level 2

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry


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