INPUT OF ATMOSPHERIC PRECIPITATION NITROGEN TO THE BALTIC SEA FROM ITS CATCHMENT

Input of atmospheric precipitation nitrogen (N) to the Baltic sea aqua torium from its drainage basin has been estimated. The deposition of n itrogen compounds on the catchment has been shown to be 5 times higher than their enter directly into the sea. An assessment of this input h as been carried out by two methods (direct and indirect) and the resul ts of calculations showed relatively high similarity. It has been demo nstrated that the main source of data uncertainty is related to the va lues of nitrogen runoff and retention in different landuse types. Depe nding on the subregions the values of atmospheric nitrogen deposition runoff to the Baltic sea changed from 5 up to 16%, the minimum values were obtained for northern subregions and the maximum - for south-west ern ones. For the whole basin of the Baltic Sea during the 1987-1991 p eriod these runoff values were 8-10% from the total amount of atmosphe ric nitrogen deposition input (1341-1401 kt) at catchment. The mean va lue was 122 kt in 1990 yr or 14% of total nitrogen input into the Balt ic Sea from all sources. The given values must undoubtedly be tal;en i nto account in various scenarios of Transboundary Air Abatement Strate gy.