NOx from ships in western Baltic Sea quantified

Atmospheric deposition of nitrogen contributes significantly to eutrophication, and accounts for about a third of the total input of nitrogen in the western Baltic Sea.

A recent study estimates that emissions of nitrogen oxides (NOx) from the shipping sector contribute up to 5 per cent of the total concentration of nitrogen in the sea, but with considerable geographic variation. The absolute contribution was found to be highest along the shoreline. However, the relative contribution was highest in offshore areas, which are less affected by riverine input of nutrients. For instance, in the centre of the Arkona Basin the share of dissolved inorganic nitrogen related to shipping could be as high as 10 to 15 per cent. The authors conclude that these offshore regions could also benefit most from reducing NOx pollution from ships.

Because the Baltic Sea was recently designated a Nitrogen oxides Emission Control Area (NECA) from 2021 onwards, new ships will have to fulfill stricter NOx emission standards. However, the overall effect is expected to be counteracted by increased shipping and the long lifetime of existing ships.

Apart from conclusions on nitrogen deposition related to shipping, the authors also conclude that future studies should focus on the relative role of other individual sectors as sources of atmospheric nitrogen.

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