Soil cracks, fractures and macropores are quite typical of natural soil structure and promote preferential flow and mass transfer. Lithological heterogeneity (e.g., soil layering, lateral and vertical bedding, channels, etc.) adds its contribution to preferential flow at higher scales. In addition to these physical factors, chemical and geochemical processes (e.g., organic matter) may promote typical hydraulic behaviors leading to preferential flow (e.g., hydrophobicity and fingering flow). This session focuses on experimental and theoretical challenges and state of the art of methods to characterize, measure, and model preferential flows and their effects on water infiltration into the soil, flow in the vadose zone, and their implications for the water-soil-plant-atmosphere continuum. The session also welcomes studies on the impact of preferential flows on mass transfer in the vadose zone of porous fractured media and heterogeneous soils. Indeed, preferential flows must play a key role regarding the efficiency of pollutant filtration by the soil (by ruling the access of pollutants to the soil sorption sites), and regarding geochemical processes that govern soil evolution, including mineral precipitation and dissolution, and weathering processes.
The proposed session will welcome studies on the following topics, but not limited to:
• Tracking preferential flows and mass transfers in soils using high-tech tracer techniques including MRI, tomography CAT, etc.
• Visualization or abstraction of the pore and fracture structure (pore size distribution, pore connectivity, type of macroporosity) or field heterogeneity (lithological and geological heterogeneity) and implications for preferential flow
• Linking preferential flow pattern with soil geochemical properties (e.g. organic matter and hydrophobicity)
• Coupling physical processes of preferential flows and geochemical processes for understanding solute sorption and solute desorption
• Coupling physical processes of preferential flow and geochemical processes for understanding mineral precipitation and dissolution (weathering processes) and impacts on soil evolution (soil erosion, crusting, etc.)
• Fracture network connectivity, its influence on volume-effective flow and mass transport dynamics, and on matrix-fracture interaction processes
• Recent theoretical developments for modeling preferential flows across scales – with scaling efforts from the pore and fracture (Ex.: the Hagen-Poiseuille equation) to the Darcian (Ex.: Darcy-Buckingham equation) and landscape (Ex.: mass balance and moisture budgeting equations) scales