Meteorological and climatological factors affecting transport and deposition of nitrogen compounds over the Baltic Sea

We studied the variation of the nitrogen deposition to the Baltic Sea with the Eulerian transport-chemistry model Hilatar. We analysed the effects of the climatological and meteorological conditions on the temporal variations of the pollution load to the sea over the period 1993–1998. The nitrogen deposition to the Baltic Sea and the concentrations at coastal stations showed strong monthly, seasonal and inter-annual variations and, apparently, no decrease with declining emissions over the period. We discuss the representativeness of coastal measurements for inferring the deposition flux to the open sea, as well as the episodicity affecting this pollution load. We also compare our results for the nitrogen deposition to the Baltic Sea with the previous estimates and discuss the implications for ecological modelling.