DECREASE IN ACID DEPOSITION - RECOVERY IN NORWEGIAN WATERS

摘要

Concentrations of sulphate in precipitation in southern Norway have decreased by 50-60% from 1980-1999. This has caused a decrease in sulphate concentrations in lakes of 30-40% from 1986-1999. Nitrogen in precipitation has decreased slightly over the last 10-years. In lakewater there has also been a significant but slight decrease. Concentrations of non-marine base cations in precipitation have decreased by 40% from 1980-1999. In lakewater, non-marine base cation concentrations have been at about the same level the last 10 years. This indicates that acid deposition has decreased sufficiently such that the pool of exchangeable base cations in the soil is now being replenished. The acidification situation in lakes in Norway has thus shown a clear improvement over the last 8-10 years. pH, alkalinity and ANC (acid neutralising capacity) have all increased. Concentrations of inorganic (toxic) aluminium species have decreased. The trends in H~+ and Al~(n+) do not follow the relation expected if Al~(n+) concentrations were governed solely by a single solid phase of A1(OH)_3.