Tracer dispersion in double porosity porous media with nonlinear adsorption

Tracer dispersion measurements in double porosity porous media with a nonlinear adsorption isotherm are reported. Thanks to a radioactive tagging technique we obtained transit time distributions at different cross-sections along the porous medium. This tagging technique allows us to work in a linear adsorption regime where classical dispersion results are used. The basic dispersion mechanisms are related to physicochemical and geometrical properties of the porous medium. We obtained satisfactory comparison of these theoretical results with experimental values. We conclude that useful information about microscopic length and time scales may be obtained from the mean tracer velocity dependence of the longitudinal dispersion coefficient. Finally, we show how the total solute concentration, due to the nonlinear adsorption isotherm, weights the trapping effects.