The project aims to monitor the transport of per- and poly-fluoroalkyl substances (PFAS) in the subsurface and unlock the potential of biochar particle injection for their remediation. PFAS are long-lasting chemicals that globally contaminate the subsurface. Due to important adsorption, the unsaturated zone plays a major role in retaining PFAS. However, decades of pollution revealed that PFAS do not remain stable but leak toward aquifers and contaminate the groundwater. The models predicting PFAS fate are applied at a large scale. They neglect small-scale interactions that control PFAS behavior and are fundamental for long‐term evolution. This is also problematic for the evaluation of remediation techniques. One of the most promising is to amend soils with biochar to stabilize PFAS in the unsaturated zone. Biochar particle injection is currently not considered for PFAS remediation, while it is successful for other contaminants and treating broader areas. However, the complex behavior of PFAS in the subsurface requires studying its effectiveness. In this project, I will address PFAS contamination and remediation effectiveness of biochar particle injection in geological porous media using the first monitoring system combining X-ray microtomography and geoelectrical acquisition. This combination is the first of its kind due to the high technical level required to set it up. Then, tank experiments with geoelectrical monitoring will be conducted for upscaling.