Reactive chemical transport within engineered barriers

We consider fully coupled geochemical process systems, and show how they may be cast as differential algebraic systems amenable to numerical solution. Considering reactive transport within engineered barriers, we motivate problems: (1) involving (some) kinetic reactions; (2) in two or more spatial dimensions; (3) incorporating spatial heterogeneity; and (4) with full coupling. The examples considered illustrate the possible treatment of spatial heterogeneity (which causes both channelled flow and stagnant water); the treatment of air-water interfaces as moving-boundaries; corrosion at interfaces; nonlinear feedback when the geochemical and flow problems are full coupled, and the formation of fingering patterns. Our preliminary calculations indicate that such problems are numerically tractable. However, verification and the availability of suitable data remain outstanding issues. Even though these problems are nonlinear, there is range of analytical tools available, and some aspects of the solution can be known quantitatively as well as qualitatively.