InterPore2026

Pore-Scale Controls on PFAS Transport in the Vadose Zone

21 May 2026, 10:05

1h 30m

Poster Presentation (MS08) Mixing, dispersion and reaction processes across scales in heterogeneous and fractured media Poster

Speaker

Valentin Grenier (Geosciences Rennes, ERC, TERA team)

Description

The vadose zone plays a central role in the transport of contaminants in continental environments. In unsaturated porous media, the coexistence of air and water gives rise to strongly heterogeneous flow and concentration fields at the pore scale. Recent studies have shown that such heterogeneity leads to dispersion and mixing behaviors that deviate markedly from predictions based on saturated flow models [1,2] . However, the implications of these anomalous transport processes for reactive contaminant transport remain poorly understood. This question is particularly relevant for assessing the fate of per- and polyfluoroalkyl substances (PFAS), which adsorb to air–water interfaces as they are transported in the vadose zone [3] .

Here, we combine laboratory tracer experiments with X-ray imaging to investigate the reactive transport of PFAS in unsaturated porous media. Breakthrough curves of PFAS are compared with those of a conservative tracer to quantify PFAS adsorption onto air–water interfaces over a range of flow rates and water saturations. To further explore the role of pore-scale heterogeneity, we manipulate the air-phase distribution by using different assemblages of fine and coarse grains. High-resolution X-ray images are then used to relate reactive transport behavior to the spatial distribution of air and water within the pore space.