Direct estimation of transport coefficients during the dissolution of an hydrocarbon pollutant in water saturated porous media. Laboratory-scale experiments and interpretation

Experiments on the dissolution and transport of trapped residual NAPLs in water saturated homogeneous porous media were carried in a laboratory column. Saturation fields among the column (ID) were measured by the gamma ray attenuation technique and the effluent pollutant concentration was measured by gas chromatography. A numerical macroscopic model based on the averaged pore-scale mass balance equations was used to simulate experiments. The model takes into account convection, dispersion and interfacial mass transfer. The mass transfer coefficient was calculated in pore-scale periodic unit cells containing the solid phase, an immobile phase (pollutant), and a flowing phase (water) by the means of averaging theory results. Confrontation of experimental and numerical results allowed the direct estimation of the mass transfer coefficient, and the construction of a unit cell which is representative of the pore-scale geometry of trapped NAPL blobs.