Contribution of Poland to Atmospheric Nitrogen Deposition to the Baltic Sea.

Poland is the second most important emission source after Germany in contributing atmospheric nitrogen deposition to the Baltic Sea basin. The main sectors contributing to reactive nitrogen emissions from Polish sources, in the period 1995-2014, are combustion and transportation, responsible together for over 97% of nitrogen oxide emissions, and agriculture responsible for over 98% of ammonia emissions. The EMEP MSC-W model with 50-km resolution was used for estimating the contribution of nitrogen emission sources from Poland to nitrogen deposition into the Baltic Sea basin and its sub-basins, in the period 1995-2014. Polish contribution in this period is mainly visible in annual wet deposition of reduced nitrogen with the range 13-18% and in wet deposition of oxidized nitrogen: 9-15%. Concerning sub-basins, a major contribution for Polish sources to total nitrogen deposition can be noticed for Baltic Proper with the range 13-19%, followed by northern sub-basins (7-18%) and finally by three western sub-basins (5-7%). Polish contribution to the Baltic Sea Basin in the year 2013 was analyzed in more detail using two models, the EMEP MSC-W model with 50-km resolution and model developed at the Institute of Meteorology and Water Management in Warsaw with 14-km resolution (IMWM Model). Both models give similar results concerning the deposition of oxidized nitrogen from Polish sources, but results show that the deposition of reduced nitrogen calculated with IMWM model is lower. The most likely reasons for the differences are different parameterizations of the deposition processes and chemical reactions in both models.