Stoddard, J.L., T.S. Traaen, and B.L. Skjelkvåle. 2001. Assessment of nitrogen leaching at UN/ECE ICP-Waters sites. Water Air Soil Pollut. 130:781-786. NHEERL-COR-2303J
The International Cooperative Programme on Assessment and Monitoring of Acidification of Rivers and Lakes (ICP-Waters) is designed to assess the degree and geographical extent of acidification of surface waters. During the last 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 between N-deposition and stages of nitrogen saturation are used to assess the importance of nitrogen leaching at the ICP-Watcrs sites in Europe and North 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 Stoddard's classification system. Significant leaching of inorganic N also occurs at most sites with deposition greater than 10 kg/ha/yr.