Parametric Investigation of Soil Retention Functions in Two-Phase NAPL-Air System

In order to examine hydraulic behavior of LNAPLs in soil، the soil retention and hydraulic conductivity curves for gasoline and water were determined using hanging column and constant head methods، respectively. The soil retention parameters were obtained based on van Genuchten، Brooks-Corey and Campbell’s models. In addition، the soil hydraulic conductivity for both fluids were predicted based on Mualem- Brooks-Corey، Burdine- Brooks-Corey، Mualem-van Genuchten and Campbell’s functions. The results indicated that the magnitudes of the pore-size distribution parameters and the bubbling pressure parameters were increased in gasoline-air system compared to water-air system. Gasoline was retained less than water owing to its negligible surface tension، yielding less needed tension to drain gasoline out from soils. The scaling of soil-gasoline retention curve was reasonably accomplished via Levrett J-function. Due to insignificant gasoline kinematic viscosity، the saturated soil hydraulic conductivity for gasoline was higher than that for water. However، under unsaturated condition soil hydraulic conductivity for gasoline was less than that for water by increasing the matric head more than approximately 30 cm water.