ABSTRACT
The pH values of most natural, river, and lake waters are in the range of 6–9. There are natural and anthropogenic sources that may influence the acidification of surface inland waters. The former depend on geological, geochemical, biological, and climatic factors. Since the 1960s, the problem of lake and river acidification has mostly been related to anthropogenic emissions of chemical compounds that have contributed to acidification either through acid deposition (SO2, NOx) or via terrestrial chemical transformations leading to H+ production (NH3/NH4 +). This entry presents a brief history of the problem of river and lake acidification. Moreover, it also focuses on the sources of this phenomenon with examples of natural and human-induced changes in freshwater pH. The environmental impact of acidification on surface inland waters is also described with a brief discussion on possible solutions to this issue
