Contaminant transport and remediation in dynamic gas-and-groundwater systems

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Groundwater is a critical natural resource, but it is a resource that is threatened by contamination. The protection and management of our groundwater relies on the development and implementation of investigation and monitoring strategies, as well as the design and operation of remediation technologies. Each of these are based on our understanding of contaminant transport in the subsurface. Although groundwater systems are often depicted as being composed of only water between mineral grains, that is not always the case. Gases exist alongside water in the pores of many groundwater systems, and these gases affect how contaminants are transported. For example, gases can be created by natural mechanisms, such as the trapping of air by the rise and fall of the water table or the generation of gases by microorganisms. They can also be created by remediation technologies, or be transferred from deeper to shallower zones through improperly sealed or damaged oil and gas wells. However, despite the widespread occurrence of gases in groundwater, their effects on contaminant transport and remediation have often been studied in isolation, considering only a single contaminant or technology. There has been little work to identify common behaviour, resulting in misinterpretation of data, incomplete conceptual models and missed opportunities for knowledge transfer between applications. This research program will conduct a coordinated investigation of multiple gas-and-groundwater applications, with specific research tasks focused on three of the most pressing environmental concerns in Canada: 1) the sustainable remediation of hazardous industrial chemicals commonly referred to as non-aqueous phase liquids (NAPLs); 2) the transport of per- and polyfluoroalkyl substances (PFAS), an emerging contaminant and global threat to water resources that is extremely resistant to degradation and hazardous to human health at very low concentrations; and 3) methane leaking from oil and gas wells into shallow aquifers, which is of particular importance as Canada tackles challenges associated with abandoned wells. The costs associated with protecting groundwater in response to each of these contaminants are measured in the billions of dollars, and they are all affected by the presence of gases in groundwater. Together, results from these research tasks will be used to develop a broad, comprehensive framework to describe and evaluate gas-based processes in contaminant transport and remediation. The research tasks will be led by a team of five graduate students (three Doctoral and two Master's). Experiments will use intermediate-scale physical models to target coupled flow and mass transfer processes, and will be combined with advanced numerical modelling to generate new knowledge to establish improved investigation and monitoring strategies, and to develop new or optimized remediation technologies to manage and protect groundwater in Canada.