AGROKÉMIA ÉS TALAJTAN 51(2002)1–2 27–36 Correspondence to: Dr. András MAKÓ, University of Veszprém, Georgikon Faculty of Agriculture, Department of Soil Science. H-8360 Keszthely, Deák F. u. 16. Hungary. E-mail: h5551mak@ella.hu Measuring and Estimating Pressure-Saturation Curves on Undisturbed Soil Samples by Using Water and NAPL A. MAKÓ University of Veszprém, Georgikon Faculty of Agriculture, Keszthely (Hungary) The ever increasing use of hydrocarbons requires huge storage and transport facilities. The threat of pollution caused by the presence of such installations and the reported cases of soil and groundwater pollution by accidental spillage has prompted an increased interest in the fate of petroleum products in soil and water (RUBIN et al., 1998). The hydrocarbon pollutants are present in liquids that are immiscible with water rather than in aqueous phase or sorbed to solids. The accurate prediction of the movement of non-aqueous phase liquid (NAPL) as a separate phase in vadose and groundwater zones is a prerequisite to the development of simulation models describing the migration and fate of organic contaminants in the subsurface. 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 measurement of the relevant P-S curves for two fluid- and, especially, three fluid media can be very time consuming or difficult. Therefore there is a paucity of primary P-S data for drainage systems representative of contaminated soils or subsoils. (There is even less information available for the primary imbibition P-S functions characterizing these environments (DEMOND & ROBERTS, 1991)). Because of this, indirect methods – based on scaling and Leverett’s assumption – are often used to predict P-S curves from data that are already available or can be measured more easily. Usually the P-S curves of air- NAPL system are obtained by scaling the air–water system (LENHARD & PARKER, 1987; FERRAND et al., 1990; BRADFORD & LEIJ, 1995). The appropriateness of this approach for handling the effect of the variation in interfacial force on capillary pressure–saturation relationships has been de- bated in the literature. The first point of contention is whether Leverett’s func- tion needs to include a dependence on the contact angle (ANDERSON, 1987; BRADFORD & LEIJ, 1995; STEFFY et al., 1997). A second problem is whether