Measurement of pressure-saturation hysteresis curves for three liquids in Vinton fine sand

Measurement of water is important in soil since this is the medium in which soil activity takes place. Pressure-saturation curves show the extent of liquid retention in the soil porous medium at different tensions during drainage and sorption (hysteresis). Measurement of soil moisture in the laboratory is time-consuming, labor-intensive and expensive. In this study, three methods for measuring pressure-saturation curves were employed, Hanging Water Column (HWC), Differential Pressure Transducer-Imbibition, and Differential Pressure Transducer-Natural. The standard HWC is compared to the other two methods which employ external manometer pressure and differential pressure transducers. Hysteresis pressure-saturation curves were determined for three liquids (water, 50% ethanol and 100% ethanol), in a homogeneous Vinton fine sand. Data was fit to the van Genuchten and Brooks Corey models and liquid capillary numbers are compared. Prediction of desorption pressure-saturation curves from water curves using relative surface tension ratios is discussed and prediction of sorption curves using relative A parameters for the drying and wetting curves. Scanning curves were scaled from the main drying and wetting curves. The capillary number-pore water velocity combination function could be another useful relationship for pressure-saturation curves.; Overall, the differential pressure transducer methods were found superior to the HWC because time consumption was reduced by more than 50% yet the results obtained were of comparable accuracy. Pressure-saturation curves for other liquids may be predicted by scaling pressure and van Genuchten α parameter with relative surface tension ratios. Hence, hysteresis curves can be obtained faster and the main disadvantages of time-consumption, labor and cost are eliminated. In addition, handling of hazardous liquids in the laboratory is minimized which is important because understanding retention of hazardous chemicals in soil is a prerequisite to achieving remediation of residual contamination. Functional relationship between the residual nonwetting phase and the capillary number or viscosity to surface tension ratio is briefly discussed.