We present a convective description of acid-base transport in porous media which is based on classical one-component nonlinear chromatographic theory applied to the acidity of the system. In the mobile phase the solution acidity is given by c=+>t-->t, where +>t and ->t are the total solution concentrations of H+ and OH-, respectively. In the stationary phase the surface acidity corresponds to the charge density &sgr;, which is commonly presented as a function of pH of the solution. The response of a chromatographic column to a step pH change at column inlet results in a pH breakthrough curve which consists of a combined chromatographic front. This combined front begins with a diffuse subfront and ends with a self-sharpening subfront. The present chromatographic theory is used to predict experimentally observed pH breakthrough curves for columns filled with materials of known pH-dependent charging behavior. Good agreement between theoretical predictions and experimental results is observed. Essentially, the same chromatographic theory is used to explain pH breakthrough curves when the salinity of the input solution is changed. This situation leads usually to an additional nonretarded front where a change in pH occurs. ¿ American Geophysical Union 1994