The effects on the air quality from Baltic Sea shipping

Shipping is a large source of air pollution, and it is therefore important to study its effect on both climate and air quality. In a project commissioned by the Swedish National Road and Transport Research Institute (VTI), SMHI has calculated the effect of Swedish shipping on the air quality in the Baltic Sea. The data has been computed by air quality experts at SMHI using the Airviro module Shipair.

VTI is since 2012 involved with the government-commisioned project Samkost. The aim is to create data for socioeconomically efficient policy instruments for transports within Sweden.

- When it comes to evaluation of costs from air pollution, VTI uses the so called Impact Pathway Approach. It means that you map the dispersion of air pollution from a certain source and investigate how it affects both nature and people, near the source and farther away. SMHI is the administrative authority in Sweden with the best expertise in this and they were therefore the ones we hired, says Lena Nerhagen, researcher and Doctor of Economics at VTI.

- We have now delivered data to VTI that describes to which degree the Swedish shipping affects the air quality around the Baltic Sea. The data relates to pollutions that cause acidification and overfertilization and that cause damage on both vegetation and peoples health, says Fredrik Windmark, air quality consultant at SMHI.

Significant local impact

In the study, the Swedish shipping in the Baltic Sea was divided into three basins; Skagerrak/Kattegatt and southern and northern Baltic Sea, and the relative impact between these three basins has been investigated. The result is the contribution from Swedish shipping to both concentrations and indices that are used to determine damage on vegetation and health.

The study from SMHI shows that even though shipping is a relatively large source of air pollution in the Baltic Sea, its impact on the total concentrations of ozone and secondary formed particles around Baltic Sea is relatively limited. Secondary particles are formed in the atmosphere through chemical reactions between air pollutants (such as nitrogen oxides). It can take a relatively long time for these particles to form, which means that they can also form far away from the source of emission. Secondary formed particles are small (mostly smaller than 2.5 micrometers).

- Locally, mostly in the regions around Stockholm and Gothenburg, the contribution from the Swedish shipping can be significant, Fredrik Windmark points out.

- Based on quantified data and evaluations of negative effects on for example forest growth or human health it is possible to estimate the costs for the society. This information is used to evaluate different types of policy instruments, like required cleaning equipment, says Lena Nerhagen.

Advanced models

Shipair, an Airviro module that was developed in collaboration with the Swedish Maritime Administration (SMA), was used to model the shipping emissions.

- With Shipair, we can get a detailed view of how the shipping industry affects the air quality. It is even possible to study the effect of single ships, says Fredrik Windmark.

Shipair uses the GPS positions of all the ships in the Baltic Sea. The positions are are collected by the AIS system (Automatic Identification System), which continuously sends the ships positions via VHS radio. All larger ships must use AIS by law, but it is very common also amonger the smaller ships.

For the regional dispersion modelling, the MATCH code developed at SMHI was used.

- Thanks to Shipair and MATCH, we can model the concentrations of air pollutions coming from all of these ships. We track about 18 000 ships per year in the Baltic Sea, which Shipair registers with 5 minute intervals, explains Fredrik Windmark.

- For most emissions, the main engine is the dominating source, but emissions from auxiliary engines and boilers are aso relevant. With Shipair, we can take into account how the main engine load varies with time, but also model the effects of for example heating and potential power supply when in port, says Fredrik Windmark.

The following results have been produced:

  • deposition of sulfur and nitrogen
  • ozone indices for damage on crops and forests (AOT40C and AOT40F)
  • concentrations and exposure of secondary particles
  • ozone indices for health effects and exposure (SOMO35)