Measuring the Two‐Phase Capillary Pressure‐Saturation Curves of Soil Samples Saturated with Nonpolar Liquids

Abstract

The simulation of multiphase fluid flow in the subsurface of soil requires that the pressure‐saturation (P‐S) relations of the porous medium be known for all fluid pairs. The objective of this study was 1) to develop a technique for routinely measuring the pressure‐saturation (PS) curves of undisturbed soil samples saturated with NAPL 2) to build a database using the measured P‐S curves and the physical, chemical properties of the soils; and 3) to establish the dependence of nonaqueous phase liquids (NAPL) retention on the other soil properties. The soils in this investigation were taken from 35 horizons of 12 soil profiles in Hungary. Undisturbed soil samples were collected from each horizon with a core sampler. The P‐S curves with NAPL were determined by using a modified pressure cell apparatus, which was designed and constructed by our laboratory. Statistical analysis was performed involving selected soil parameters and the measured NAPL retention data. By the application of the linear regression equations, the NAPL retention curves can be calculated directly from the mechanical fractions, bulk density, and humus content values of the soil in question. The comparison of estimated and measured NAPL retention data demonstrates the improvement gained by using the regression approach instead of the Leverett type scaling method. The scaling method significantly underestimates the NAPL retention. The accuracy of this new estimation method (after extending the database) can be useful for modeling NAPL fate and migration or mapping the organic contaminant sensitivity of the soils.