Preferential and non-uniform flows are induced by biotic and abiotic factors and processes (roots, wet-dry and freeze-thaw cycles, lithology) as well as anthropogenic activities (e.g. tillage and cultivation, mining activity). In consolidated porous fractured systems, the vadose zone may reach a thickness of several hundred meters and preferential flow paths are commonly associated with discontinuities (fissures, fractures, etc). The understanding of preferential flow (PF) is of premium importance in relation to soil surface and catchment hydrology. PF can move a considerable amount of water and solutes (pollutants and bacteria) from the soil surface to groundwater bodies. PF shortens the residence time in the vadose zone and reduces pollutant contact with the soil reactive particles. Therefore, the importance of understanding preferential flow processes cannot be overstated, regarding the fate and transport of solutes, nutrients and contaminants in agricultural land, landscapes, catchments, mine waste covers and tailings storage facilities. This session welcomes studies on experimental and theoretical challenges aimed to identify, quantify, and model the physical processes involved in preferential flows and their impacts on mass transfers in porous media across scales (from pore scale to catchment scale):
• Understand the geometry and connectivity, formation and dynamics of fissure, fractures and macropores;
• Understand the effect of physical processes and geochemical processes on the dynamics of macropores and fracture networks;
• Develop and refine models for quantifying preferential flow, from pore scale to pedon scale and entire catchments and landscapes;
• Unpacking the pore structure of soil using new methods and approaches, including the use of non-Newtonian fluids, for improved characterization of heterogeneous soils and preferential flow.
• Effects of preferential flows on solute, nutrient or contaminant transport in the saturated and unsaturated zone;
• Coupling the physical processes of preferential flows and geochemical processes for improving the understanding of solute sorption and desorption, mineral precipitation and dissolution;
• Modelling of the effect of preferential flow on mass transport across scales, from pore scale to pedon scale and entire catchments and landscapes.