Effect of Macropore Density and Connectivity On Solute Transport in Saturated Soils.

Among the foremost issues in the area of hydrological sciences is the estimation of infiltration fluxes and the associated contaminant exchange from the near-surface to the ground water table. Macropores are ubiquitously found in the subsurface and have a significant impact on hydrological processes. The presence of macropores lead to preferential water flow through the unsaturated soils, which is not well described by a Darcy approach to flow through porous media (Gerke and van Genuchten, 1993). Macroporous flows through soils have important consequences for sustainability of ground water quantity and quality since they can rapidly water, transport solutes and pollutants through soils. Classical Richards equation and advection-dispersion equation, on which traditional infiltration and transport calculation are based, depend on the assumption that flow velocities in soil are small and the flow pattern is laminar. In macroporous soils, this assumption is often violated. Water flow and solute movement through macropores can be affected by the density of the macropores, size of macropores,  the presence of clay coatings, biological activity, the vertical flow rates, and the extent of ‘direct connectivity’ between the macropores and with the surface. In this research, we reexamine the effects of macropore density’s effects as well as their connectivity on solute transport in saturated soils.