Fresh water from rivers and lakes varies in acidity/alkalinity
depending on the rocks and soils it runs over. Granite country
yields water that is slightly acidic, while water from limestone
country is slightly alkaline. Acidity and alkalinity are measured
on a pH scale, on which 7 is neutral, values below 7 are acidic and
values above 7 are alkaline. pH can change due to pollution or due
to waste from biomass such as algae.
A certain river, fed by various...