Transport of ion‐exchanging solutes in groundwater: Chromatographic theory and field simulation

Equations describing the transport of ion‐exchanging solutes governed by local chemical equilibrium through a saturated porous medium are well established in the literature. Concentration profiles resulting from the numerical solution of the general multispecies equations typically exhibit unusual and complicated features such as multiple fronts and plateau zones. This paper presents an analytical framework, based upon the theory of chromatography, which permits a priori characterization of certain key concentration profile features. The cases studied include both homovalent and heterovalent exchange in binary and ternary systems. In order to test its validity, the chromatographic analysis is applied to a field project involving direct injection of advanced treated municipal effluent into an aquifer. All of the major features observed in the available field data are accurately predicted by the chromatographic theory.