Investigation of Possible Nutrient Sources in Estonian Rivers

A statistical model MESAW was used to estimate the diffuse emission coefficients of nitrogen in Estonia. This includes analysis of data on loads, point sources, land use types etc. Two studies were conducted to determine the emission coefficients for the whole Estonia and for a smaller study area near Tallinn. Investigations showed that in addition to arable lands, drained peat soils can be a significant source of nitrogen. In fact, our results show that the unit-area loads from drained peat soils may be 1.5 to 2.3 times higher than from arable lands. Additional detailed investigations and measurements are needed to support these conclusions. Comparison of emission coefficients for the whole Estonia and of the Tallinn catchment area indicated that the coefficients can vary significantly between sources and single years. Therefore it is suggested that the sources of nitrogen loads should be defined in a catchment area level rather than a country level.