Small-scale models in the form of random walks, combining Gaussian jumps, advection by mean flow field and possibly very long sorbing durations, correspond to experimental data in many porous media, in the laboratory and in the field. Within this frame-work, solutes are observed in two phases,...

A Boltzmann-like model for the description of processes of outgassing and contamination is proposed. The cavity /oR2, where the contaminants migrate during their motion from the source region /oR1 to the target /oR3, contains a random medium.