Experimental and Theoretical Investigations of Fundamental Processes Relevant to Chemical Oxidation of Dense Nonaqueous Phase Liquids in Fractured Rock

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Project Summary/Abstract The objective of this research is to carry out experimental, computational and theoretical investigations of fundamental processes involved in oxidation-reduction reactions in fractured rock systems, encompassing natural redox processes and processes relevant to environmental remediation. We will focus on oxidation of an entrapped immobile fluid phase within fractures, and oxidation of dissolved species/solid mineral phases within the rock matrix that are accessed by the oxidant via matrix diffusion. The influence of the reaction products on medium alteration, and associated feedback on flow and transport properties will also be quantified. Experiments on oxidation of free-phase NAPL within fractures will be carried out at Lawrence Livermore National Laboratory in collaboration with Dr. Russell Detwiler, in a non-intrusive experimental system where high-resolution quantitative measurements can be performed while visualizing the complex consequences of oxidation, including MnO2 generation and transport. Experimental studies and computational/theoretical modeling of chemical oxidation of dissolved NAPLs in the rock matrix will be carried out at the University of Colorado to investigate the movement of an oxidation front into a rock matrix by diffusion and the role of fracture-matrix interactions in the transport of oxidant. The concept of "reaction front diffusivity" and self-similar solutions for the concentration profiles will be pursued to develop theoretical understanding of reaction-diffusion fronts, and three-dimensional simulations will be pursued to evaluate the consequences of matrix heterogeneity. The influence of fracture-matrix interactions on oxidant transport will be investigated in controlled laboratory experiments and computational models will be developed to predict behavior of oxidation-reduction processes in complex fractured rock masses. Broader Impacts: Educational activities will involve synergy with an internal grant ($25,000, P.I. Rajaram) from the Engineering Excellence Fund at the University of Colorado (CU). The objective of this grant is to modernize the educational laboratories for porous media, and its scope will be greatly enhanced by adding a reactive transport component. The P.I.'s Department hosts a REU site in environmental engineering, through which undergraduate students will be recruited to participate in this research. An educational web site devoted to oxidation-reduction reactions in fractured rock masses will be developed in the later stages of the project, including a bibliography of relevant literature, basic tutorials illustrating fundamental processes, animations of experimental results and simple computer codes that may be downloaded freely. We will also develop synergy with consulting companies focused on applying oxidation technologies in fractured rock sites for remediation or water quality assessment.