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© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  05 Oct 2020

05 Oct 2020

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This preprint is currently under review for the journal ACP.

Effects of marine fuel sulfur restrictions on particle number concentrations and size distributions in ship plumes at the Baltic Sea

Sami Seppälä1, Joel Kuula1, Antti-Pekka Hyvärinen1, Sanna Saarikoski1, Topi Rönkkö2, Jorma Keskinen2, Jukka-Pekka Jalkanen1, and Hilkka Timonen1 Sami Seppälä et al.
  • 1Atmospheric Composition Research, Finnish Meteorological Institute, Helsinki, 00560, Finland
  • 2Aerosol Physics Laboratory, Tampere University, Tampere, 33100 Finland

Abstract. Exhaust emissions from shipping are a major contributor to particle concentrations in coastal and marine areas. Previously, marine fuel sulfur content (FSC) was restricted globally to 4.5 m/m% but the limit was changed to 3.5 m/m% at the beginning of 2012 and further down to 0.5 m/m% in January 2020. In sulfur emission control areas (SECA), the limits are stricter; FSC restriction was originally 1.50 m/m% but it decreased first to 1.00 m/m% in July 2010 and again to 0.10 m/m% in January 2015. In this work, the effects of the FSC restrictions on particle number concentrations (PNC) and size distributions (NSD) are studied at the Baltic Sea SECA. Measurements were made on a small island (Utö, Finland; 59° 46’50N, 21° 22’23E) between 2007 and 2016. Ship plumes were extracted from the particle number size distribution data, and the effects of the FSC restrictions on the observed plumes as well as on the total ambient concentrations were investigated. Altogether 42 322 analyzable plumes were identified during the 10-year measurement period. The results showed that both changes in the FSC restrictions reduced the PNC of the plumes. The latter restriction (to 0.10 m/m% in January 2015) decreased also the total ambient particle number concentrations, as a significant portion of particles in the area originated from ship plumes that were diluted beyond the plume detection limits. The overall change in the PNC of the plumes and ambient air was 27 and 32 %, respectively, for the total FSC change from 1.50 to 0.10 m/m%. The decrease in plume particle number concentration was caused mostly by a decrease in the concentration of particle sizes of ∼35–134 nm. The latter restriction also reduced the count median diameter of the particles, which was probably caused by the fuel type change from residual oil to distillates during the latter restriction. The PNC was larger for the plumes measured in daytime compared to those measured in nighttime likely because of the photochemical aging of particles due to UV-light. The difference decreased with the reducing FSC indicating that lower FSC has also an impact on the atmospheric processing of ship plumes.

Sami Seppälä et al.

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Sami Seppälä et al.

Sami Seppälä et al.


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Publications Copernicus
Short summary
Effects of fuel sulfur content restrictions implemented by the International Maritime Organization at the Baltic Sea, in July 2010 and January 2015, on the particle properties of ship exhaust plumes and ambient aerosol were studied. The restrictions reduced the particle number concentrations and median particle size in plumes and number concentrations in the ambient aerosol. These changes may improve human health in coastal areas and decrease the cooling effect of the exhaust emissions of ships.
Effects of fuel sulfur content restrictions implemented by the International Maritime...