Assessment of nitrogen leaching ICP-Waters sites (Europe and North America)

The International Cooperative Programme on Assessment and Monitoring of Aci dification of Rivers and Lakes (ICP-Waters) is designed to assess the degre e and geographical extent of acidification of surface waters. During the la st 20 years, international emission reduction measures in Europe and North America have resulted in a decrease in atmospheric S-deposition of up to 50 %, while N-deposition has stayed almost constant. Empirical relationships b etween N-deposition and stages of nitrogen saturation are used to assess th e importance of nitrogen leaching at the ICP-Waters sites in Europe and Nor th America. There is a clear coherence between high N saturation stages and high N deposition loads and more than 50% of the analysed ICP Waters sites show a high degree of nitrogen saturation, defined as stages 2 or 3 in Sto ddard's classification system. Significant leaching of inorganic N also occ urs at most sites with deposition greater than 10 kg/ha/yr.