Per- and polyfluoroalkyl substances (PFAS) are persistent contaminants increasingly detected across terrestrial environments, from contaminated source zones and soils to the vadose zone, groundwater, and urban subsurface systems. PFAS persistence, mobility, complex sorption behaviour, precursor transformations, and interactions with air-water and soil-water interfaces in heterogeneous subsurface environments present challenges for understanding and predicting their long-term environmental fate. This session aims to bring together experimental, field-based, modelling, and remediation studies addressing PFAS as well as other emerging or traditional contaminants in terrestrial systems.
We welcome contributions that:
• Advance understanding of PFAS retention and mobilisation, source-zone behaviour, mass flux, transformation processes, and the performance and longevity of remediation technologies
• Explore the influence of hydroclimatic variability, including changing recharge, drought, snowmelt, and extreme precipitation.
• Map new contaminant pathways to soil and groundwater, including transport through urban subsurface environments and bedrock, where heterogeneous geological structures, preferential flow, infrastructure, and complex recharge conditions can influence contaminant migration.
• Investigate soil-bedrock-groundwater interactions and emerging approaches for identifying and quantifying these pathways
By connecting process understanding, field observations, modelling, and remediation, the session seeks to identify lessons learned, emerging challenges, and new pathways for predicting and managing persistent contamination in vadose zone and groundwater systems.

Topics include:
• PFAS/Contaminant fate and transport in vadose zone and groundwater systems, including surface water interactions
• Sorption, interfacial processes, precursor transformations, and PFAS mass flux
• Remediation technologies and long-term performance, including in-situ and on-site methods for stabilization, separation and destruction
• Hydroclimatic and hydrogeological controls on PFAS mobilization and groundwater contamination
• Model development and modelling studies
• Urban and bedrock transport pathways connecting contaminated terrestrial environments to groundwater
• Site characterization