Influence of Physicochemical Properties of Soil on pH of Pore Water

pH of soil pore water is the important factor in heavy metal retention and migration in soil. Buffer capacity of clays such as kaolinite, hectorite, attapulgite, and Na-bentonite were determined. The magnitude of buffer capacity is in the order of hectorite>Na-bentonite>attapulgite>kaolinite. Carbonate content and CEC of soil affect most on the magnitude of buffer capacity while effects of organic content and surface area were negligible. Attempts were made to simulate buffer capacity experimental results in this research. In order to model the buffer capacity of soil, chemical interactions between proton and surface functional group were modeled using the diffuse double layer theory. An empirical model as functions of carbonate content and CEC were proposed as well. Predictions made by the diffuse double layer model agreed with experimental results well.