Groundwater contaminant transport with adsorption and ion exchange chemistry: Method of characteristics for the case without dispersion

Contaminant transport in the groundwater environment with adsorption and ion exchange reactions is considered. For the case where the influence of dispersion is negligible, the method of characteristics is used to formulate the solution for any adsorption isotherm and an arbitrary number of exchanging cations. The approach applies equally well to linear flow systems and to nonlinear systems along streamlines in a nonuniform flow field. Transport problems related to the emerging technologies of in situ gasification of lignite and in situ leach mining of uranium are discussed. The first example considers migration of organics using the nonlinear Freundlich isotherm for adsorption of organics on lignite. Other examples consider ammonia migration and site restoration using the mass action law of ion exchange chemistry in in situ leach mining of uranium.