Pathways of dye tracer movement through structured soils on a macroscopic scale
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abstract
Structural features, biopores, and slickensides have been reported to be important features impacting bypass flow of pollutants to shallow groundwater aquifers. The objectives of this research were to identify the pathways of water and solute transport at a macroscopic scale and to identify visible characteristics of solute flow in two Vertisols and one Alfisol. Relative involvement of structural features in solute transport, such as ped interfaces, root channels, and slickenside planes, were studied by mapping dye flow paths. Roots and interpedal pores served as major pathways of transport in all three soils. Slickenside fissures in Vertisols served as minor pathways of solute transport. Solute flow along slickenside surfaces was observed primarily when the dye solution was delivered to the surface of the slickenside via the adjacent root channel. The differences in observed distribution of dye pathways were related to the abundance of different types of structural features, their apparent continuity, interconnectivity, and macropore access to the infiltrating dye front. Lateral transport was identified as one of the major components of the flow, even though the sites were located on nearly-level to gently sloping geomorphic surfaces.
