19 May 2022
19 May 2022
Status: this preprint is currently under review for the journal ACP.

Measurement Report: Small effect of regional sources on black carbon properties and concentrations in Southern Sweden background air

Erik Ahlberg1, Stina Ausmeel1,a, Lovisa Nilsson1, Mårten Spanne2, Julija Pauraite3, Jacob Klenø Nøjgaard4,b, Michele Bertò5, Henrik Skov4, Pontus Roldin1, Adam Kristensson1, Erik Swietlicki1, and Axel Eriksson6 Erik Ahlberg et al.
  • 1Division of Nuclear Physics, Lund University, Box 118, 221 00 Lund, Sweden
  • 2Environment Department, City of Malmö, 208 50 Malmö, Sweden
  • 3Department of Environmental Research, Center for Physical Sciences and Technology, Savanorių ave. 231, 02300 Vilnius, Lithuania
  • 4Department of Environmental Science, iClimate, Aarhus University, Roskilde, Denmark
  • 5Laboratory of Atmospheric Chemistry, Paul Scherrer Institute (PSI), 5232 Villigen PSI, Switzerland
  • 6Ergonomics and Aerosol Technology, Lund University, Box 118, 221 00 Lund, Sweden
  • anow at: Swedish Environmental Protection Agency, 10648 Stockholm, Sweden
  • bnow at: National Research Centre for the Working Environment, 2100 Copenhagen, Denmark

Abstract. Soot, or black carbon (BC), aerosol is a major climate forcer with severe health effects. The impacts depend strongly on particle number concentration, size and mixing state. This work reports on two field campaigns at nearby urban and rural sites, 65 km apart, in southern Sweden during late summer 2018. BC was measured using a single particle soot photometer (SP2) and Aethalometers (AE33). Differences in BC concentrations between the sites are driven primarily by local traffic emissions. Equivalent and refractory BC mass concentrations at the urban site were on average a factor 2.2 and 2.5 higher than at the rural site. Peaks in rush hour BC mass concentrations at the urban site were up to a factor ~4 higher than the background levels. The number fraction of particles containing a soot core was significantly higher in the city. BC particles at the urban site were on average smaller by mass and had less coating owing to fresh traffic emissions. The organic components of the fresh plumes were similar in mass spectral signature to “hydrocarbon-like organic aerosol” (HOA), commonly associated with traffic. Despite the intense local traffic (~30 000 vehicles passing per day), PM1, including organic aerosol, was dominated by aged continental air masses even at the curbside site. The fraction of thickly coated particles at the urban site was highly correlated with the mass concentrations of all measured chemical species of PM1, consistent with aged, internally mixed aerosol. Trajectory analysis for the whole year showed that air masses arriving at the rural site from eastern Europe contained approximately double the amount of BC compared to air masses from western Europe. Furthermore, BC from the largest region emissions in the Malmö/Copenhagen urban area transported to the rural site is discernable above background levels only when precipitation events are excluded.

Erik Ahlberg et al.

Status: open (until 04 Jul 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-156', Anonymous Referee #1, 03 Jun 2022 reply
  • RC2: 'Comment on acp-2022-156', Anonymous Referee #2, 27 Jun 2022 reply

Erik Ahlberg et al.

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Ahlberg et al 2022 ISSA figure data Erik Ahlberg

Erik Ahlberg et al.


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Short summary
To investigate the properties and origin of black carbon particles in southern Sweden during late summer, we performed measurements both at a rural site and the nearby city of Malmö. We found that local traffic emissions of black carbon led to around twice as high concentrations compared to the rural site. Modelling show that these emissions are not clearly distinguishable at the rural site, unless meteorology was favourable, which shows the importance of long-range transport and processing.