| Use of well-characterized porous media can improve the efficiency of laboratory subsurface hydrologic studies. We present a comprehensive set of hydrological properties for commercially-available silica sands. Four different sand grades were characterized for physical properties, chemical composition, water retention, three-phase saturation-pressure relationships, saturated and unsaturated hydraulic conductivity. Sand properties included narrow particle size distribution, high chemical purity and low organic matter content. Water retention curves featured well-defined air entry pressures. (in press, Soil Science Society of America Journal).; Predicting light nonaqueous-phase liquid (LNAPL) movement in heterogeneous subsurface environments is critical for designing effective remediation schemes. To develop a method for predicting the shape and extent of LNAPL lenses in the capillary fringe of the vadose zone, two-dimensional experiments were performed in a glass chamber (50 cm x 60 cm x 0.95 cm) using characterized silica sands and two LNAPLs (Soltrol{dollar}spcircler{dollar} 220, Duoprime{dollar}spcircler{dollar} 55 Mineral Oil). LNAPLs were released in water-wetted sands to simulate a point-source discharge above a water table. Light transmission was used to delineate the changing LNAPL lens boundary during infiltration. At equilibrium, no zone above the capillary fringe remained at NAPL saturations higher than the residual saturation. A previously published model was tested. Discrepancies between measured and predicted lens thicknesses were found when model equations were modified to a fully explicit form. (published in Journal of Contaminant Hydrology).; To investigate LNAPL movement in the vicinity of sloping textural interfaces, two-dimensional experiments were conducted in the glass chamber using two sand grades (12/20 and 30/40 sieve sizes) to create fine-over-coarse interfaces. Soltrol{dollar}spcircler{dollar} 220 was released at the sand surface under constant water irrigation, simulating a point-source discharge. Light transmission was used to observe water and LNAPL flow paths. LNAPL movement strongly depended on the water saturation in the fine layer above the interface. Extensive lateral spreading of LNAPL along the interface was observed in most cases. These experiments demonstrated the critical role water saturation plays in determining LNAPL disposition in heterogeneous vadose environments. (submitted to Water Resources Research). |
