Nitrogen deposition has not declined similar to the decline in S deposition. Most deposited N is retained in soils and vegetation and is not leached. Trends in nitrate in surface waters are positive, negative and neutral contrary to predominantly downwward trends in sulphate. There is some evidence of reduced nitrate concentrations in regions where N deposition has declined. Elsewhere, trends in nitrate in surface waters are suggested to be related to climate, forest growth and N saturation or are simply not understood.   Acid-sensitive ecosystems are continually enriched with nitrogen which increases the chance of nitrate leaching resulting in acidification and eutrophication.