Advancing non-invasive geoelectrical methods for imaging soil and groundwater contaminants

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Contamination of soil and groundwater by hazardous chemicals, including chlorinated solvents and coal tar (known as dense nonaqueous phase liquids (DNAPLs)) and other anthropogenic chemicals such as per- and polyfluoroalkyl substances (PFAS), remains a serious problem worldwide. Approximately 24,000 federal contaminated sites exist in Canada alone, including former industrial lands, decommissioned refineries, and abandoned gas stations. In 2019, the Federal Contaminated Sites Action Plan was renewed for 15 years, with the federal government pledging $1.16 billion for the first five years (2020 to 2024). Of this, $1.05 billion has been assigned to remediate contaminated sites. Successful remediation requires accurate knowledge on where the contaminants are, and how quickly they are being removed. Since conventional methods, including boreholes and monitoring wells, are intrusive, costly and provide limited information, rapid and cost-effective methods providing continuous information on the subsurface are highly desirable. Geoelectrical techniques are non-invasive imaging methods that can `look' below the surface, much like an MRI scan, to detect features of interest. These techniques, which include electrical resistivity tomography (ERT) and induced polarization (IP), are seeing increasing application in environmental investigations. Since they measure the spatial variation of electrical properties, and contaminants typically have distinct electrical properties relative to groundwater (i.e., resistive DNAPL, conductive AMD), geoelectrical techniques have outstanding potential as investigative tools at contaminated sites. However, their common application has not been realized, due in part to the lack of tools and experience in interpreting geoelectrical responses from heterogeneous contaminant distributions in the subsurface. The ultimate goal of this research program is to establish geoelectrical techniques as field-proven tools for contaminated site investigations, including characterization and remediation activities. ERT is the most mature technique but requires critical research to jump to pilot-scale field trials. IP is newer and exciting but needs fundamental work to prove its value for certain contaminants and scenarios. In the short-term, this research program will focus on: (i) building the foundation for IP as a technique for mapping contaminated sites, (ii) translating initial success of ERT to pilot test field implementation, and (iii) launching geoelectrical techniques for mapping key emerging contaminants. The program is timely and is supplemented by the recent, transformative improvements occurring in geoelectrical imaging. It is expected to be a game changer in the remediation industry, leading to significant benefits to the Canadian environment and economy. Furthermore, it will train 3 MESc students, 2 PhD students and 5 undergraduate students and prepare them for key positions in the fast-growing environmental sector.