Multiscale Approaches in Reactive Transport Modeling

The field of reactive transport lies at the intersection of several disciplines in the Earth and Environmental sciences, including hydrology, geochemistry, biology and geology. The processes in natural and engineered media that are the focus of study of these disciplines take place over a wide range of spatial and temporal scales. Specifically, geological media are characterized by their physical and mineralogical heterogeneity at spatial scales from nanometers to hundreds of meters and beyond. Flow and advection of solutes take place at the scale of individual pores but are commonly represented at the Darcy scale where the porous medium is treated as a continuum. A large contrast is often observed between fluid residence times in regions of enhanced permeability such as fractures or macropores and less permeable media where diffusion may be the dominating solute transport process. Understanding of reactive processes, including those mediated by microorganisms, is often developed at the molecular scale in the laboratory but their impact in the environment is observed at larger spatial scales.