Los Angeles smog - secondary pollution

The acidity of aqueous solutions is frequently described in terms of the pH scale. Acids (Box 3.3) give rise to hydrogen ions (H+) in solution and the pH value of such a solution is defined  

However, pH is related to pOH through the equilibrium describing the dissociation of water  

It is important to notice that this is a logarithmic scale, so it is not appropriate to average pH values of solutions (although one can average H+ concentrations). 

On the pH scale, 7 is regarded as neutral. This is the point where aH+ = aOH. There are a number of other important values on the scale (conventionally made to stretch from 0 to 14) that are relevant to the environment. 

Forest Humid Soils with soils arable soils CaC03 

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