Stored heat in buildings, asphalt, etc. Increase nighttime convective circulation. Together with plant uptake, 5.2 units are put back into essentially the top soil but 3.1 units of that runs off leaving 2.1 units in the top soil. The only topsoil removal mechanism, however, is bacteria which process the sulfur at a rate of 1.0 units per year. We measure acid rain in terms of the pH index.
Water is neutral.
The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic.