The importance of nitrate in acidification has been evaluated for 163 sites uncluded in ICP on Waters in 13 countries in Europe and North America. At 63 % of these sites yearly average nitrate concentrations amounted to more than 10 % of the acid non-marine acid anions. This shows that nitrate leakage contributes significantly to acidification at a majority of the ICP sites. High leakage of nitrogen occur only at sites with high nitrogen concentrations in precipitation and high total deposition of nitrogen (wet+dry). 144 ICP sites were classified according to Stoddard's system for stages of nitrogen saturation. Approximately one half of the sites had a high degree of nitorgen saturation (Stage 2 or 3). There was a clear coherence between stage classification and total N deposition

Convention on long-range transboundary air pollution

Norwegian State Pollution Control Authorities(SFT)