Atmospheric Contribution to Eutrophication of the Baltic Sea

Abstract

Nitrogen and phosphorus are two main nutrients responsible for eutrophication of the Baltic Sea. Almost all phosphorus is entering the sea via rivers, whereas 20–30% of nitrogen is deposited from the air. Therefore, there is a need for monitoring atmospheric nitrogen deposition to the Baltic Sea. Time series of annual nitrogen depositions to the Baltic Sea have been calculated for the period 1995–2015 with the same version of the EMEP MSC-W model. They show significant inter annual fluctuations due to changes in meteorological conditions from one year to another. To reduce the influence of meteorological conditions on the results the so called “normalized” depositions have been also calculated. They indicate a clear decline of annual depositions of oxidized nitrogen to the Baltic Sea and only minor decline of reduced nitrogen depositions in the considered period. Emissions from Germany and Poland are the main sources contributing to deposition of oxidized nitrogen to the Baltic Sea basin followed by the ship traffic on the Baltic Sea and on the North Sea. Transportation and combustion are the main emission sectors contributing to oxidised nitro-gen deposition, whereas, agriculture is the dominating emission sector contributing to reduced nitrogen deposition.