Preprints
https://doi.org/10.5194/acp-2020-1282
https://doi.org/10.5194/acp-2020-1282

  21 Jan 2021

21 Jan 2021

Review status: this preprint is currently under review for the journal ACP.

Measurement report: The influence of traffic and new particle formation on the size distribution of 1–800 nm particles in Helsinki: a street canyon and an urban background station comparison

Magdalena Okuljar1, Heino Kuuluvainen2, Jenni Kontkanen1, Olga Garmash1, Miska Olin2, Jarkko V. Niemi3, Hilkka Timonen4, Juha Kangasluoma1, Yee Jun Tham1, Rima Baalbaki1, Mikko Sipilä1, Laura Salo2, Henna Lintusaari2, Harri Portin3, Kimmo Teinilä4, Minna Aurela4, Miikka Dal Maso2, Topi Rönkkö2, Tuukka Petäjä1, and Pauli Paasonen1 Magdalena Okuljar et al.
  • 1Institute of Atmospheric and Earth System Science/Physics, Faculty of Science, University of Helsinki, FI-00014, Helsinki, Finland
  • 2Aerosol Physics Laboratory, Physics Unit, Tampere University, PO Box 692, FI-33014, Tampere, Finland
  • 3Helsinki Region Environmental Services Authority, PO Box 100, FI-00066, Helsinki, Finland
  • 4Atmospheric Composition Research, Finnish Meteorological Institute, PO Box 503, FI-00101, Helsinki, Finland

Abstract. Most of the anthropogenic air pollution sources are located in urban environments. The contribution of these sources to the population of atmospheric particles in the urban environment is poorly known. In this study, we investigated the aerosol particle number concentrations in a diameter range from 1 to 800 nm at a street canyon site and at a background station within 1 km from each other in Helsinki, Finland. We use these number size distribution data together with complementary trace gas data and develop a method to estimate the relative contributions of traffic and atmospheric new particle formation (NPF) to the concentrations of sub 3 nm particles. During the daytime, the particle concentrations were higher at the street canyon site than at the background station in all analyzed modes: sub 3 nm particles, nucleation mode (3–25 nm), Aitken mode (25–100 nm), and accumulation mode (100–800 nm). The population of sub-3 nm and nucleation mode particles was linked to local sources such as traffic, while the accumulation mode particles were more related to non-local sources. Aitken mode particles were dominated by local sources at the street canyon site while at the background station they were mainly influenced by non-local sources. The results of this study support earlier research showing direct emissions of the sub 3 nm particles from traffic. However, by using our new method, we show that during NPF events, traffic contribution to the total sub-3 nm particle concentration can be small and during daytime (6:00–20:00) in spring it does not dominate the sub-3 nm particle population at either of the researched sites. In the future, this method can be applied to estimate the contribution of traffic to particle number concentrations in different urban environments. This knowledge is needed to evaluate the effects of traffic on urban air quality.

Magdalena Okuljar et al.

Status: open (until 18 Mar 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'review Comment on acp-2020-1282', Anonymous Referee #1, 14 Feb 2021 reply
  • RC2: 'Comment on acp-2020-1282', Anonymous Referee #2, 22 Feb 2021 reply

Magdalena Okuljar et al.

Magdalena Okuljar et al.

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Short summary
To estimate the relative contribution of different sources onto the particle population in an urban environment, we conducted simultaneous measurements at the street canyon and the urban background station in Helsinki. We investigated the contribution of traffic and new particle formation onto particles with a diameter between 1 and 800 nm. We found that during spring traffic does not dominate the particles smaller than 3 nm at either of the stations.
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