Mechanism of acid-neutralization in two Japanese watersheds

In Japan, acidification of terrestrial water has not yet been reported except lakes acidified by volcano or mine. However, acid deposition in Japan is as much as those in northern Europe and north-eastern U.S.A., and acidification of terrestrial water may occur in future. In order to predict long-term acidification, it is necessary to understand acid-neutralization mechanism in watershed. Therefore, two experimental watersheds study for geology, hydrology, and water chemistry were conducted. On the basis of these data, chemical change in percolation of precipitation through watersheds and acid-neutralization mechanism are analyzed. The principal results are: (1) Acid deposition is neutralized continuously in percolation of precipitation from ground-surface to aquifer, (2) Chemical weathering of primary minerals plays an important role in the acidneutralization in the watersheds, and should be quantified and taken into account in the long-term prediction of acidification.