Cracks, fractures and macropores are typical features of natural soils and fissured rock formations, 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 larger 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 finger 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 fractured porous media and heterogeneous soils. Preferential flows are expected to regulate the access of pollutants and solutes to soil reactive particles, and thus the efficiency of pollutant removal by soils and the geochemical processes that govern soil evolution and weathering processes (e.g., precipitation / dissolution processes). On larger scales, some landforms, such as mine waste covers are known to have highly heterogeneous properties, and yet quantifying and modelling water and solute movement in these systems is often required for regulatory and management purposes.
The proposed session will welcome studies including but limited to the following topics:
• 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 the physical processes of preferential flows and geochemical processes for understanding solute sorption and solute desorption, and mineral precipitation and dissolution
• Fracture network geometry and 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 to the Darcian and landscape scales
• Quantification and modelling of water flow and solute transport within heterogeneous substrates and complex geological structures such as mine wastes (e.g. tailings and waste rocks), mine waste covers and rocky/gravelly substrate