What does the symbol PH stand for in geography?

Well, the PH table is the table for acidity. The higher the number is (it goes up to fourteen) the more basic or alkaline it is. At a PH of 7 the solution or soil or whatever in question is neither acidic or basic. At a PH of, say 2 it is rather acidic.

In Geography PH is used in reference to acid rain and the acidity in lakes or in soils and how they can effect local animal populations.

I hope that helped.