Abstract
The reversal of water acidification has been recently indicated by both empirical data and experiments. The world's largest whole‐ecosystem “experiment” involving ~30% and ~40% reduction in nitrogen and sulfur emissions, respectively, has occurred in Central Europe due to the political and economic changes in the postcommunist countries since 1989. Parallel decreases in deposition rates of SO 4 2− , NO 3 − , and NH 4 + have resulted in a rapid reversal in hydrochemistry of acidified lakes in the Šumava Mountains and the High Tatra Mountains. Concentrations of SO 4 2− and NO 3 − in lakes were reduced by 11–14 and 13–32 mmol m −3 , respectively, between the late 1980s and middle 1990s. Leaching of calcium, magnesium, and aluminum from the watersheds decreased while lake water pH and alkalinity increased. The immediate decline in NO 3 − concentrations after reduced nitrogen emissions has suggested a rapid reversibility of nitrogen saturation of the mountainous ecosystems in response to decreased amounts of nitrogen deposition.