Numerical Modeling of Reactive Chemical Transport under Non-isothermalConditions in Porous and Fractured Media

摘要

Subsurface contamination problems of metals and radionuclides are ubiquitous.Metals and radionuclides may exist in the solute phase or bound to soil particles andinterstitial portions of the geologic matrix. Accurate tools to reliably predict themigration and transformation of these metals and radionuclides in the subsurfaceenvironment enhance the ability of environmental scientists, engineers and decisionmakers to analyze their impact and to evaluate the efficacy of alternative remediationtechniques prior to incurring expense in the field. A mechanistic-based numericalmodel could provide such a tool. This paper communicates the development andverification of a mechanistically coupled fluid flow and reactive chemical transportunder both fast and slow reactions in variably saturated porous and fractured media.Theoretical bases, numerical implementations, and modeling experiments of themodel will be described. Two example problems will be presented. The first onewill be a reactive transport problem to elucidate the non-isothermal effects onheterogeneous reactions. The second problem involves coupled fluid flow andreactive transport in fractured media. It purposes are to examine the effects ofprecipitation and dissolution on fluid flow and matrix diffusion. It would help shadesome lights on the retardation ability of grain matrices on the migration of metals andradionuclides.