Trends in acidification
The deposition of sulphur has been reduced in Europe during the last 15 years, but further reductions are needed. A new sulphur protocol was signed in Oslo in June 1994. Although many European countries have agreed upon a sulphur reduction of 70-80 % by the year 2010 relative to 1980, acidification will still be a problem for many decades in large areas of southern Norway. No large scale reductions in nitrogen deposition has been achieved and acidification due to nitrogen compounds seem to be more important relative to sulphur in the future.
Time lags for water quality improvements following acid deposition reductions may be expected. This is probably due to the effects of long-lasting deposition of acid compounds and corresponding increased transport of base cations from the acidified areas. Recovery may take decades, as seen in Norway, where the positive effects of a 30 percent reduction in sulphur deposition over the last 15 years have been registered over the last three years only.
Due to the time lags liming may probably be longer lasting than recognized from sulphur deposition scenarios.

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