  We address the description of solutes flow with trapping processes in porous
media. Starting from a small-scale model for tracer particles trajectories, we
derive the corresponding governing equations for the concentration of the
mobile and immobile phases. We show that this formulation is fairly general and
can easily take into account non-constant coefficients and in particular
space-dependent sorption rates. The transport equations are solved numerically
and a comparison with Monte Carlo particle-tracking simulations of spatial
contaminant profiles and breakthrough curves is proposed, so to illustrate the
obtained results.
