Numerical study on kinetic/equilibrium behaviour of dissolution of toluene under variable subsurface conditions

Abstract

Estimating the extent of kinetic/equilibrium behaviour of dissolution is essential for selecting remediation strategy for highly soluble aromatic constituents of petroleum present in the subsurface. Present study aims at numerically simulating dissolution and transport of toluene under the effect of sorption and biodegradation to understand their synergistic influence during the tailing phase. Subsurface conditions influencing mass transfer such as porous media properties, flow velocity and volumetric residual saturation of toluene entrapped in the pore space are varied and their impacts are assessed. The numerical results in terms of dimensionless numbers suggest that influence of soil grain size and porosity are most significant in calculating the extent of mass transfer limitation. Increases in the volumetric residual saturation results in prolonged near-equilibrium condition for dissolution especially for fine-grained porous media. Tailing is found to be prolonged for sand with low saturations and high flow velocities indicating the importance of mass transfer limitation for the estimation of total clean-up time.