Abstract
Wettability profoundly affects the distribution of residual NAPL contaminants in natural soils. Under conditions of preferential NAPL wettability, residual NAPL is retained within small pores and in the form of thick films along the corners and crevices of the pore walls. For the same NAPL content, preferential NAPL wettability increases the interfacial area for mass-transfer and modifies considerably the hydrodynamic conditions at the pore scale. Thick NAPL films in pore corners provide capillary continuity between NAPL-filled pores, dramatically influencing the dynamics of NAPL dissolition to a flowing aqueous phase by convection and diffusion. Physicochemical and pore structure parameters affecting the stability of thick NAPL films are thus expected to affect the dissolution behaviour. This is shown here using a 2D quasi-static pore network simulator. The pore space is idealized as a network of cubic pores connected by square tubes following respective distributions. We study the effects of initial NAPL distribution, pore structure and disjoining pressure on NAPL dissolution dynamics. Rupture of weak NAPL films causes disconnection of the NAPL phase into distinct clusters. Capillary equilibrium is assumed to exist within each cluster. Quasi-state drainage and fingering of the aqueous phase into NAPL-filled pores in each cluster is treated as an invasion percolation process and a stepwise procedure is adopted for the solution of flow and solute concentration fields. Macroscopic behaviour (effluent concentration and NAPL recovery with time is explained in terms of NAPL cluster evolution and local hydrodynamic conditions. NAPL film stability critically affects the rate of mass transfer, such as that stable NAPL films provide for more rapid dissolution. The network simulator reproduces the essential physics of wetting NAPL dissolution in porous media and explains the concentration-tailing behaviour observed in experiments suggesting also new possibilities for experimental investigation.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
