In this paper, we have studied the behaviour of reactive solute transport through stratified porous medium under the influence of multi-process nonequilibrium transport model. Various experiments were carried out in the laboratory and the experimental breakthrough curves were observed at spatially placed sampling points for stratified porous medium. Batch sorption studies were also performed to estimate the sorption parameters of the material used in stratified aquifer system. The effects of distance dependent dispersion and tailing are visible in the experimental breakthrough curves. The presence of physical and chemical non-equilibrium are observed from the pattern of breakthrough curves. Multi-process non-equilibrium model represents the combined effect of physical and chemical non-ideality in the stratified aquifer system. The results show that the incorporation of distance dependent dispersivity in multi-process non-equilibrium model provides best fit of observed data through stratified porous media. Also, the exponential distance dependent dispersivity is more suitable for large distances and at small distances, linear or constant dispersivity function can be considered for simulating reactive solute in stratified porous medium.

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This paper presents the behavior of solute transport through mobile-immobile (MIM) soil column based on the laboratory study. The study considers that the advective-dispersive transport equation is used for mobile domain, and the solute exchange between two liquid domains is described as the firstorder process. A numerical model is developed for the MIM advective-dispersive transport equation including equilibrium sorption and the first-order degradation. Afterward, the numerical model is used to simulate experimental breakthrough curves (BTCs) for transport of chloride and fluoride through heterogeneous soil column using constant, linear, and exponential distance-dependent dispersion models. It is shown that the behavior of concentration profile produced with a constant dispersion model is similar to the distance-dependent dispersion model. It is found that the constant dispersion and the exponential distance-dependent dispersion models simulate experimental BTCs reasonably well as compared to the linear distance-dependent dispersion model. Hence, the exponential distancedependent dispersion model is a simple and practical approach to describe the solute transport through the MIM porous media.

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