Experimental investigation and numerical modeling of light nonaqueous phase liquid dissolution and transport in a saturated zone of the soil

The present research aims at studying the dissolution and transport process of benzene as a light nonaqueous phase liquid (LNAPL) in saturated porous media. This process is studied under unidirectional flow at different water velocities ranging from 0.90 to 3.60 cm/h in a three-dimensional saturated sand tank (100 cm × 40 cm × 35 cm). This tank represents a laboratory-scale aquifer. The dispersion parameters of the sand tank are based on an independent tracer experiments. The experimental aquifer is simulated by developing a three-dimensional finite element numerical model. This model assumes that the dissolved concentration along the LNAPL-water interface is equal to the solubility concentration. The numerical model results overpredict the experimental within factor 1.6 and 2.29 at depths of 1 cm and 3 cm, respectively, during eight days. The correlation coefficient is ranging from 0.8485 to 0.9986. The time invariant average mass transfer coefficient is determined at each interstitial velocity. The values are ranged from 0.016 to 0.061 cm/h (i.e. increased with velocity toward a limiting value). For a circular benzene pool, two linear relationships are found; the first between the overall Sherwood number (Sh(e)*) with average Peclet number in x-direction (Pex(e)*); and the second between the overall Sherwood number (Sh(e)*) with average Peclet number in y-direction (Pey(e)*).