How acidic is acid rain?
Acidity and alkalinity are measured on a scale known as the pH (potential for Hydrogen) scale. It runs from 0 to 14. Since it is logarithmic, a change in one unit equals a tenfold increase or decrease of acidity/alkalinity. Therefore a solution of pH 2 is 10 times more acidic than a solution of pH 3 and 100 times as acidic as a solution of pH 4. Zero is extremely acid, 7 is neutral, and 14 is extremely alkaline. Any rain below pH 5.0 is considered acid rain, although some scientists set the limit at 5.6. Normal rain and snow containing dissolved carbon dioxide (a weak acid) measure about pH 5.6. The acidity of rain varies according to geographical area. Eastern Europe and parts of Scandinavia have rain with a pH of 4.3 to 4.5; in the rest of Europe the rain is pH 4.5 to 5.1; in the eastern United States and Canada it ranges from 4.2 to 4.6; and in the Mississippi Valley it’s 4.6 to 4.8. The…
