4. pH of rain
pH is one of the important indices of rain. However, the relationship between
pH value and acid concentration, in other words, the concentration of hydrogen
ion, is rather complex. The lower the pH value is, the higher the hydrogen
ion concentrations are. Hydrogen ion concentrations increase more rapidly
in lower pH values. pH values depend on the balance of acid and base. Even
if rain contains a high concentration of nitric and sulfuric acids and
has a low pH, the pH value will become higher with more bases like ammonium.
We, therefore, may have problems with rain with high pH. We need to pay
due attention to the concentrations of sulfuric and nitric acids as well.