Autor: Jordi Petchamé

Abstract:

Reactive transport is the phenomenon resulting from the interaction and coupling of solute transport and chemical reactions. The transport equation is a linear PDE that represents mass balance of aqueous species undergoing advection (displacement of particles dragged by fluid flow) and dispersion (spreading due to velocity fluctuations and molecular diffusion). If these species are involved in chemical reactions, we must include the contribution of these reactions to the mass balance. This yields a nonlinear PDE which governs the evolution of the species concentrations, and must be solved numerically. Some applications are groundwater pollution, geologic carbon storage, groundwater remediation or biodegradation. We are developing a chemical mixing code using object-oriented programming in Fortran that contains all the chemical information of a system, including: species, phases, reactions, concentrations of species, and different types of reactive zones. The idea is that this code reads all the chemical information of a system, and performs reactive mixing computations using transport data (such as mixing ratios) as procedure arguments. Roughly speaking, this code will turn a transport code into a reactive transport code. Regarding the numerical methods, we have used the Water Mixing Approach (WMA) method which fully decouples transport and chemical reactions, and so facilitates parallelisation.