Investigating the chemical response of groundwater systems to micro-earthquakes

Mark Stillings

Prof. Rebecca Lunn ( Academic Supervisor )

Dr. Sally Thompson ( Industrial Supervisor )

Prof. Zoe Shipton

Lake Räterichsboden in summer above the Grimsel Test Site, Switzerland.

Project Overview

Earthquakes (even micro-earthquakes) can change groundwater composition by opening new fractures, mixing different water sources, and trigger chemical reactions. This project looks at how we can understand a groundwater system, develop a baseline, and identify any earthquake-induced changes to the baseline groundwater chemistry. Regular groundwater chemical monitoring and development of new water tracing techniques were developed and employed at an underground test site in Switzerland next to a nearby surface water reservoir. Repeated draining and refilling of the reservoir induced tiny micro-earthquakes while groundwater chemistry and earthquake activity were monitored. Monitoring revealed large pH drops (1-3 units) in groundwater coinciding with micro-earthquakes within the same area. We used laboratory experiments to explore the mechanisms of earthquake-induced pH changes in the groundwater. The project findings are significant as pH exerts a fundamental control of chemical and biological reactions in groundwater, and micro-earthquakes are ubiquitous worldwide.

Groundwater sampling in tunnels providing access to subsurface boreholes

Why Strathclyde

Projects with Strathclyde were appealing due to a combination of factors. Strathclyde were approached by an industrial partner to work with them to develop and deliver a project scope. Collaboration of academia and industry from the project outset ensured that project deliverables were in the interest of both parties. The project's multidisciplinary nature meant different academic expertise and analytical facilities were required. Strathclyde was an attractive option. The project team has access to facilities with a diverse background and a proven track record delivering projects of a similar nature. As a PhD student, what made the project inviting to work on was the reputation of the academics, department and the project's multidisciplinary nature, which you would not usually find in a PhD project.

Lake Räterichsboden in winter during the draining of the reservoir

Researcher Impact

Completing a PhD as part of university-industry collaboration provided me with experiences and opportunities additional to those accessible to non-industrial PhD projects. As part of my PhD, I had regular contact with other companies from different countries, giving me a better understanding of radioactive waste disposal programs worldwide. My industrial partner provided me with regular one-on-one support and training workshops delivered by leading industrial consultants. This additional contact with experts allowed me to discuss the data produced from my PhD and learn new techniques enhancing my PhD thesis and its industrial outputs. Industrially partnered post-graduate projects give real-world context. The industrial-academic collaboration brought about an interesting multidisciplinary project, leading to a more well-rounded and higher impact project.

Tunnels at the Grimsel Test Site, Switzerland

Business Impact

RWM will deliver a highly engineered facility for the underground disposal of the nation’s higher activity radioactive waste. To do this, it is necessary to characterize the geological setting at depth, as well as possible groundwater pathways between the packaged waste and the surface environment over very long timescales.

The project strengthened capability within RWM and its academic and laboratory supply chain (Strathclyde) regarding the current, and emerging approaches, tools and techniques that can be used to evaluate groundwater migration and chemistry. This knowledge directly supports RWM’s plan for borehole investigations and informs our testing and analytical strategy.

The collaborative nature of the broader project, involving Strathclyde, RWM and the other international project partners, leveraged learning benefits. Of particular value was the integration of results from the seismic data project with the groundwater chemistry information. This provided insight on the interoperability of field techniques, and the additive benefit to site characterization outcomes through integration of information from a range of geological disciplines.

The novel follow-on project, using BioTracers in groundwater, offers potential for a passive technique for tracing groundwater flow. This has interest due to the potential cost savings enabled by the technique compared to more conventional methods.