ReCAp - The Relevance of Impacts by Climate Change and Anthropogenic Activity for DNAPL Source Zone Formation

• Applicant: Dr. Christian Engelmann
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 499973567

Subsurface contamination by dense non-aqueous phase liquids (DNAPLs) can cause adverse effects for humans and the environment, with high potential for threatening the safety of groundwater resources serving as major source for water supply. With natural attenuation of water-dissolved DNAPLs as typical remediation approach, despite a range of subsurface exploration techniques, the fate of DNAPL-contaminated sites remains unclear due to insufficient data and knowledge on source zones acting as long-term entities for contamination. In addition, climate change and anthropogenic activity may jointly create new hazard potentials by inducing hydraulic and thermal stressors potentially affecting source zones. A robust understanding of the processes associated with DNAPL source zone formation under changing conditions is crucial to ensure an efficient assessment of contaminated sites.The project ReCAp aims at systematically investigating the transient dynamics of DNAPL source zone formation to evaluate the relevance of changing external stressors compared to other system properties. By employing experimental and model-based methodologies, a simplified three-phase flow system will be evaluated at the laboratory scale (physical aquifer models). Changing external stressors (hydraulic, thermal) will be mimicked through defined variation signals (groundwater level, subsurface temperature). For this, hydrological measurement and climate projection data of representative sites will be analysed to define a range of lab-scale simulation scenarios. Reflective optical imaging in combination with an image processing and analysis framework will be performed to generate experimental observation data for phase saturation distribution. The latter data will be used for calibrating a numerical multiphase flow model implemented in the software suite TOUGH. For this, a multi-criteria objective function considering proxy source zone properties will be coupled to a semi-automated inverse modelling approach (e.g., PEST++). Finally, a statistical analysis varying parameters subject to measurement uncertainty will be conducted to delineate the relevance of changing externals stressors compared to subsurface and fluid phase properties.The scientific output is expected to be of value not only for an improved understanding of source zone formation under changing system conditions, but will also contribute to an optimization of laboratory methods for the visualisation of phase migration dynamics. In the future, the project results may be the base for the development of process-driven models carefully verified against robust, laboratory-scale observation data.

• DFG Programme: Research Grants
• International Connection: Australia, Norway, USA
• Cooperation Partners: Professorin Dr. Helen Kristine French; Kaveh Sookhak Lari, Ph.D.; Professor Charles J. Werth, Ph.D.