Study finds substantial increase in nanoparticles in air as it crosses the Baltic Sea; shipping emissions responsible for about half
A study by a team of international researchers has found that air crossing over the main basin of the heavily ship-trafficked Baltic Sea shows a “substantial” increase in the number of 50–400 nm particles (50–400N). An open-access paper on their work is published in the journal Oceanologia.
The researchers evaluated 10 months worth of data (September 2009 to June 2010) of atmospheric aerosol particle number size distribution at three atmospheric observation stations along the Baltic Sea coast: Vavihill (upwind, Sweden); Utö (upwind, Finland); and Preila (downwind, Lithuania).
|Air mass trajectories passing over the upwind stations and arriving at Preila: smaller dots represent individual hourly trajectories; larger dots represent the mean of trajectories. Kecorius et al. Click to enlarge.|
They used the differences in aerosol particle number size distributions between the upwind and downwind stations during situations of connected atmospheric flow, when the air passed each station, to assess the contribution of ship emissions to the aerosol number concentration (diameter interval 50–400 nm) in the Lithuanian background coastal environment.
They found that 26–53% of particles arriving at Preila were generated by processes and emissions taking place between the upwind stations and Preila.
The particle number concentration increased by a factor of 1.9 from Utö to Preila (the average total number concentration at Utö was 791 cm−3), and by a factor of 1.6 from Vavihill to Preila (the average total number concentration at Vavihill was 998 cm−3).
Almost half of the measured particles stem from sea traffic emissions, while the rest is deemed to be mainly from cars but also biomass combustion, industries and natural particles from the sea.
The observed increase was the sum of all emissions and processes taking place during the air transport between the sites. These include differences in boundary layer height, growth of pre-existing particles or new particles formed between the sites, land-based emissions between the sites, sea salt emissions, and emissions from ship traffic. The potential contribution of each source was discussed, and shipping was found to be the only source that could explain most of the change. Furthermore, the observed changes were in line with other published ship emission studies.—Kecorius et al.
Simonas Kecorius, Niku Kivekäs, Adam Kristensson, Thomas Tuch, David S. Covert, Wolfram Birmili, Heikki Lihavainen, Antti-Pekka Hyvärinen, Johan Martinsson, Moa K. Sporre, Erik Swietlicki, Alfred Wiedensohler, and Vidmantas Ulevicius (2015) “Significant increase of aerosol number concentrations in air masses crossing a densely trafficked sea area” Oceanologia doi: 10.1016/j.oceano.2015.08.001