Biogeochemical processes in groundwater and the vadose zone with an emphasis on gas and solute fluxes across environmental interfaces

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Environmental interfaces can be defined as regions along which different compartments of the hydrologic system meet and interact. These compartments include the saturated zone of aquifers, the unsaturated zone containing water and soil gas, surficial soils, and surface water bodies. Processes associated with these compartments are often studied in isolation. However, it is common that the degree of biochemical reactivity is highest at the interfaces between the compartments. As a result, processes at interfaces play an important role in local, regional and global biogeochemical balances, and can have significant impacts on gas and solute fluxes migrating from one region to another. Specific objectives addressed in this proposal include the quantification of surficial emissions of toxic hydrocarbons together with gaseous biodegradation products such as carbon dioxide and methane at crude oil and biofuel spill sites, the investigation of the inadvertent transfer of chlorinated solvents from contaminated groundwater to soil gas during remediation activities, and the development of a numerical model that describes the migration of metals towards the ground surface above buried ore bodies. Together, these studies will contribute to the overarching objective of my research program to develop and quantify mechanistic conceptual models for transport and reaction processes involving environmental interfaces, with an emphasis on shallow groundwater systems. These objectives will be achieved through integrated field, laboratory, and modeling studies. The research program as a whole will lead to environmental and economic benefits. At hydrocarbon and biofuel spill sites, the work will allow for an improved assessment of contaminant longevity. The study will also shed light on increased risks for soil vapor intrusion into buildings due to groundwater remediation and biodegradation of biofuels, including an assessment of the potential for development of an explosive atmosphere in basements near biofuel spill sites. The research program will also extend state-of-the-art modeling techniques to applications in mineral exploration, generating knowledge that can be used to locate buried ore bodies.