%0 Conference Proceedings %T Impact of structural heterogeneity on solute transport andmixing in unsaturated porous media: An experimental study %+ Géosciences Rennes (GR) %A Borgman, Oshri %A Gomez Serito, Francesco %A Le Borgne, Tanguy %A Méheust, Yves %< avec comité de lecture %B European Geosciences Union General Assembly 2022 (EGU22) %C Vienna, Austria %P EGU22-10554 %8 2022-05-23 %D 2022 %Z Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] %Z Sciences of the Universe [physics]/Earth Sciences/HydrologyConference papers %X Solute transport in unsaturated porous media plays a crucial role in environmental processesaffecting soils, the unsaturated zone, and aquifers lying below. These processes include nutrientand pesticide leaching in soils, contaminant migration to aquifers and degradation in the vadosezone, and nutrient exchange at the soil-river interface, to name a few. Natural porous media arecharacterized by structural heterogeneity in the pore sizes disorder and their spatialarrangements. The impact of pore size heterogeneity on the spreading and mixing of a soluteplume, and the resulting reaction rates, are not well understood for unsaturated flow. In addition,these processes can be affected by incomplete mixing at the pore scale. Thus, direct pore-scaleexperimental measurements are needed to gain a comprehensive understanding of the mixingstate of the system. Our goals are to 1) study the impact of structural heterogeneity on fluid phasedistributions and 2) establish how the arrangement of fluid phases impacts solute spreading andmixing. We use micromodel experiments with two-dimensional porous media. The samples arecreated by placing an array of circular posts in a Hele-Shaw-type flow cell. We vary theheterogeneity by controlling the circular posts’ diameters disorder and correlation length of theirspatial distribution. In the first stage of each experiment, we simultaneously inject liquid and air toestablish an unsaturated flow pattern with a connected liquid phase cluster. Then, we introduce aconservative fluorescent solute pulse with the moving liquid phase. We track the soluteconcentration and gradients’ evolution by taking periodic images of the flow cell and analyzingtheir fluorescence intensity. In addition to unsaturated flow experiments, our system allows us tostudy the impact of pore size disorder and correlation on solute mixing in saturated porous mediaand even directly quantifying fast reaction products’ concentrations. Initial results confirmprevious findings on the impact of desaturation on enhanced mixing rates for a single porousmedium geometry. In addition, our use of a continuous solute pulse highlights regions thatmaintain a high mixing rate at the interface between mobile and stagnant liquid phase parts.Ongoing experiments explore the impact of increasing pore size disorder and correlation lengthon fluid phase distributions and mixing rates. %G English %L insu-03693752 %U https://insu.hal.science/insu-03693752 %~ INSU %~ UNIV-RENNES1 %~ UR2-HB %~ CNRS %~ GR %~ OSUR %~ GIP-BE %~ UR1-HAL %~ UR1-SDLM %~ GR-DIMENV %~ UNIV-RENNES2 %~ OSUR-OSU %~ TEST-UR-CSS %~ UNIV-RENNES %~ INRAE %~ UR1-ENV %~ GR-TERA %~ TEST3-HALCNRS %~ TEST4-HALCNRS %~ TEST5-HALCNRS