ACIDIFICATION TRENDS IN SURFACE WATERS IN THE INTERNATIONAL PROGRAM ON ACIDIFICATION OF RIVERS AND LAKES

We applied trend analyses to data from the International Cooperative P rogramme for Acidification of Rivers and Lakes in an attempt to discov er regional patterns of long-term changes in surface water chemistry b oth in Europe and North America, and to relate these changes to trends in deposition. Decreases in surface water SO42- concentrations predom inated at European sites in the Federal Republic of Germany, The Nethe rlands, and in Norway, and at the North American sites in Ontario, Can ada, the Adirondacks and Catskill Mountains of New York, U.S.A. Other predominating trends in the European sites were decreasing Ca2+ concen trations at many of the sites in The Netherlands, Norway, and Sweden. Increases in NO3.- were observed at several sites in southern Norway, and in the Adirondack and Catskill regions of eastern New York. This, combined with an increased occurrence of declining base cation concent rations may well be responsible for the lack of documented surface wat er recovery from acidification. Despite region-wide trends in several variables of importance in acidification, no correlations between surf ace water trends and changes in deposition were found using these data .