29 Apr 2021

29 Apr 2021

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

Sources of black carbon at residential and traffic environments

Sanna Saarikoski1, Jarkko V. Niemi2, Minna Aurela1, Liisa Pirjola3,4, Anu Kousa2, Topi Rönkkö3, and Hilkka Timonen1 Sanna Saarikoski et al.
  • 1Atmospheric Composition Research, Finnish Meteorological Institute, Helsinki, FI-00101, Finland
  • 2Helsinki Region Environmental Services Authority (HSY), Helsinki, FI-00066, Finland
  • 3Aerosol Physics Laboratory, Physics Unit, Tampere University, Tampere, FI-33014, Finland
  • 4Department of Automotive and Mechanical Engineering, Metropolia University of Applied Sciences, Vantaa, 01600, Finland

Abstract. This study investigated the sources of black carbon (BC) at two contrasting urban environments in Helsinki, Finland; residential area and street canyon. The sources of BC were explored by using positive matrix factorization (PMF) for the organic and refractory black carbon (rBC) mass spectra collected with a soot particle aerosol mass spectrometer (SP-AMS). Two sites had different local BC sources; the largest fraction of BC originated from biomass burning at the residential site (38 %) and from the vehicular emissions at the street canyon (57 %). Also, the mass size distribution of BC diverged at the sites as BC from traffic was found at the particle size of ~100–150 nm whereas BC from biomass combustion was detected at ~300 nm. At both sites, a large fraction of BC was associated with urban background or long-range transported BC indicated by the high oxidation state of organics related to those PMF factors. The results from the PMF analysis were compared with the source apportionment from the aethalometer model calculated with two pair of absorption Ångström values. It was found that several PMF factors can be attributed to wood combustion and fossil fuel fraction of BC provided by the aethalometer model. In general, the aethalometer model showed less variation between the sources within a day than PMF being less responsive to the fast changes in the BC sources at the site. The results of this study increase understanding of the limitations and validity of the BC source apportionment methods in different environments. Moreover, this study advances the current knowledge of BC sources and especially the contribution of residential combustion in urban areas.

Sanna Saarikoski et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-231', Anonymous Referee #1, 31 May 2021
  • RC2: 'Comment on acp-2021-231', Anonymous Referee #2, 08 Jul 2021

Sanna Saarikoski et al.

Sanna Saarikoski et al.


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Short summary
This study presents the main sources of black carbon (BC) at two urban environments. The largest fraction of BC originated from biomass burning at the residential site (38 %) and from vehicular emissions (57 %) at the street canyon. Also, a significant fraction of BC was associated with urban background or long-range transport. The data are needed by modelers and authorities when assessing climate and air quality impact of BC as well as directing the emission legislation and mitigation actions.