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 Programme forAcidification of Rivers and Lakes in an attempt to discover regional patterns of long-term changesin surface water chemistry both in Europe and North America, and to relate these changes totrends in deposition. Decreases in surface water SO ₃ ^- concentrations predominated at European sites in theFederal Republic of Germany, The Netherlands, and in Norway, and at the North American sitesin Ontario, Canada, the Adirondacks and Catskill Mountains of New York, U.S.A. Otherpredominating trends in the European sites were decreasing Ca²⁺ concentrations at many of thesites in The Netherlands, Norway, and Sweden. Increases in NO ₃ ^- were observed at several sites in southern Norway, and in theAdirondack and Catskill regions of eastern New York. This, combined with an increasedoccurrence of declining base cation concentrations may well be responsible for the lack ofdocumented surface water recovery from acidification. Despite region-wide trends in severalvariables of importance in acidification, no correlations between surface water trends and changesin deposition were found using these data.