The proposed research will reconsider two basic processes in hydrogeology: Solute transport through formations with heterogeneous hydraulic conductivity, and chemical mixing and reaction in porous media. The educational initiative will consist of building new classroom tools that combine physical models with numerical simulation, and developing projects that integrate graduate education with local hydrogeologic issues.
When does spatially variable hydraulic conductivty cause dispersion and when does it cause nonequilibrium mass transfer? Hydrogeologists and soil scientists have found that spatial heterogeneity in permeability strongly influences the transport of solutes in groundwater. Researchers are divided between two principal schools of thought. The first models the effects of heterogeneity as a mass-transfer (or dual-porosity) process, and parameterizes the size of immobile zones. The second models the effects based on heterogeneity on transport as a dispersive, usually Fickian, process and relates an effective (or macro) dispersion coefficient to the spatial statistics of the permeability field. We will conduct experimental and theoretical research to determine the conditions under which each model is appropriate. In particular, we will investigate the type of spatial structures that give rise to diffusive mass transfer.
How do chemicals mix and react to porous media? Developing accurate models of reaction in porous media hinges on accounting for the way molecules meet each other before they can react, and mechanical dispersion and chemical mixing (or pore-scale mixing) may not be synonymous. For example, mechanical dispersion may result, in part, from solute movement through some pores, but not through adjacent pores.
Combining physical demonstrations and numerical modeling. Students gain understanding of the connection (and differences) between natural processes and mathematical models by using physical models simultaneously with numerical models in the classroom. The combination gives students insight into the relation of conceptual/mathematical models and physical reality. The two will be joined by using an LCD projector to display the visual output of a numerical transport simulation directly onto a demonstration tank, superimposing the simulated and real dye plumes.
Integrating hydrogeology and policy. Students will be engaged in local hydrologic issues by involvement in a nonprofit organization that provides environmental and hydrologic expertise for local communities.
