ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-11-1803-2011 Atmospheric deposition of nitrogen to the Baltic Sea in the period 1995–2006 Bartnicki J. 1 Semeena V. S. 1 Fagerli H. 1 Norwegian Meteorological Institute, Oslo, Norway 19 01 2011 11 1 1803 1834 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/11/1803/2011/acpd-11-1803-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/11/1803/2011/acpd-11-1803-2011.pdf

The EMEP Unified model has been used to compute atmospheric nitrogen deposition into the Baltic Sea basin for the period of 12 years: 1995–2006. The level of annual total nitrogen deposition into the Baltic Sea basin has changed from 230 Gg N in 1995 to 199 Gg N in 2006, decreasing 13%. This value corresponds well with the total nitrogen emission reduction (11%) in the HELCOM Contracting Parties. However, inter-annual variability of nitrogen depositions to the Baltic Sea basin is relatively large, ranging from −13% to +17% of the averaged value. It is mainly caused by the changing meteorological conditions and especially precipitation in the considered period. The calculated monthly depositions are similar for most of the years showing maxima in the autumn months October and November. The source allocation budget for atmospheric nitrogen deposition to the Baltic Sea basin was calculated for each year of the period 1997–2006. The main emission sources contributing to total nitrogen deposition are: Germany 18–22 %, Poland 11–13% and Denmark 8–11%. There is also a significant contribution from distant sources like the United Kingdom 6–10%, as well as from the international ship traffic on the Baltic Sea 4–5%.

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