One method for remediating contaminated groundwater is to introduce a chemical solution that will react with and degrade the contaminant. This remediation method is most successful if the introduced chemical solution is spread throughout the contaminated area. The porous materials through which groundwater flows are naturally heterogeneous, meaning that water flows more easily through some parts and less easily through others. This heterogeneity naturally causes some spreading, called passive spreading, of the chemical solution into the contaminated groundwater. Additional spreading, called active spreading, can occur by inducing certain time-varying patterns of groundwater flow in the contaminated area. Certain time-varying flows, classified as chaotic advection, are known to substantially enhance active spreading.
Both passive and active spreading lead to enhanced degradation of the contaminant; however, the combined effect of active and passive spreading is not well understood. In this project, a suite of laboratory experiments and numerical simulations will be used (1) to investigate the interplay between passive and active spreading and the role that each plays in enhancing degradation, and (2) to develop strategies for designing chaotic advection patterns for different patterns of heterogeneity. The laboratory experiments will be conducted using novel laser-based optical techniques to visualize and quantify the combined effects of passive and active spreading on contaminant degradation.
Activities such as remediation of contaminated groundwater, extraction of geothermal energy, and certain types of mining of metals all rely on spreading of chemical solutions in porous geological materials. Because of the natural heterogeneity of geological materials, an understanding of the relationship between heterogeneity and chaotic advection and their effects on spreading is critical to the success of these applications. This project will also develop new laboratory techniques that could provide a breakthrough in measurement of reactive transport in porous media.
