|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|||||||
|
|
|
|
|
|
|
|
|
||
pH
pH is the quantity that we use to
measure acidity, as you will recall from high-school chemistry. pH is the
negative logarithm of the number of hydrogen ions.
pH ranges from 0 to 14, with 7 being neutral, less than 7 being acidic, and
greater than 7 being basic. Therefore a liquid with a pH of 4 is ten times as
acidic as one of pH 5 and 100 times as acidic as one of pH of 6.
Natural precipitation is not perfectly neutral, because of dissolved CO2 which gives it a pH of about 5.65. Therefore, precipitation is considered acidic if it has pH less than about 5.6. Airborne soil particles in the western United States are somewhat more basic and give precipitation in that region a higher natural pH, whereas in the eastern United States natural particulates tend to make precipitation (even in the absence of anthropogenic contributions) slightly more acidic.
PREVIOUS: Sulfur and Nitrogen Compounds
NEXT: Effects of Acid Deposition