Acidification trends in surface waters in the International Program on Acidification of Rivers and Lakes

The authors applied trend analyses to data from the International Cooperative Programme for Acidification of Rivers and Lakes in an attempt to discover regional patterns of long-term changes in surface water chemistry both in Europe and North America, and to relate these changes to trends in deposition. Decreases in surface water SO42- concentrations predominated at European sites in the Federal Republic of Germany, The Netherlands, and in Norway, and at the North American sites in Ontario, Canada, the Adirondacks and Catskill Mountains of New York, USA. Other predominating trend sin the European sites were decreasing Ca2+ concentrations 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 action concentrations may well be responsible for the lack of documented surface water recovery from acidification. Despite region-wide trends in several variables of important in acidification, no correlations between surface water trends and changes in deposition were found using these data. 47 refs., 6 figs., 6 tabs