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Modeling NAPL dissolution from pendular rings in idealized porous media
Citation:
Huang, J., J. Christ, M. Goltz, AND A. Demond. Modeling NAPL dissolution from pendular rings in idealized porous media. WATER RESOURCES RESEARCH. American Geophysical Union, Washington, DC, 51(10):8182-8197, (2015).
Impact/Purpose:
Submitting to Water Resources Research.
Description:
The rate of NAPL dissolution often governs the clean-up time for subsurface hazardous waste sites. Most formulations for estimating this rate are empirical and assume that the NAPL is the non-wetting fluid. However, field evidence suggests that some waste sites might be organic-wet. Thus, formulations that assume the NAPL is non-wetting may be inappropriate for estimating the rates of NAPL dissolution. An exact solution to the Young-Laplace equation assuming a hexagonal close packing of uniform solid spheres provides a theoretical prediction for non-aqueous phase liquid (NAPL) interfacial area, and, in turn, the rate of dissolution in situations where the NAPL is the wetting phase. In this model, the NAPL is assumed to reside as pendular rings around the contact points between the spheres, which, when coupled with Fick’s law for diffusion, enables the prediction of a theoretical dissolution rate. A comparison of the predictions of this theoretical model with predictions from empirically-derived formulations from the literature for water-wet systems showed a consistent range of dissolution values, despite the different model foundations (water-wetting vs NAPL-wetting, theoretical vs. empirical).
