Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Estimating Interfacial Areas for Multi-Fluid Soil Systems

Authors
item Bradford, S - UC RIVERSIDE
item Leij, F - UC RIVERSIDE

Submitted to: Journal of Contaminant Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 23, 1996
Publication Date: N/A

Interpretive Summary: Insoluble organic compounds, such as gasoline and other petroleum products, are common contaminants in soils where they pose a significant danger to water supplies. In soils containing air, water, and oil; there may be air-oil, air-water, and oil-water interfaces as well as three fluid- solid interfaces. Knowledge of the fluid-fluid and fluid-solid contact areas is important in soil science, hydrology, and environmental and petroleum engineering. Estimates of the contact area help us understand how the fluids are distributed in the soil - better estimates for the unsaturated hydraulic properties may be obtained with this information. The effectiveness of bioremediation of contaminated soils depends on the oil-water area; micro-organisms will locate themselves at the contact area where they have access to both inorganic nutrients and organic contaminants. Unfortunately, the direct measurement of the contact areas is still cumbersome. We present methods to estimate the contact areas from the relationship between capillary pressures and fluid saturations. The magnitude of fluid-fluid and solid-fluid areas depends greatly on the different fluid saturations and interactions between the solid and the fluid.

Technical Abstract: Knowledge of the fluid-fluid and fluid-solid interfacial areas is important to better understand and quantify many flow and transport processes in porous media. This paper presents estimates for interfacial areas of porous media containing two or three fluids from measured Pc-S relations, using the thermodynamic treatment of two-fluid Pc-S relations by Morrow [1970]. For two-fluid systems (air-oil, air-water, oil-water) the solid- nonwetting interfacial area (AsN*) equals zero when the solid is completely wetted by the wetting fluid and the area under the Pc-S curve was directly proportional to the nonwetting-wetting interfacial area (ANW*). If the solid surface was not completely wetting by one fluid, ANW* and AsN* were estimated by weighed partitioning of the area under the Pc-S curve. For porous media with fractional wettability, the procedure for media with uniform wettability was applied separately to water-and oil-wet regions. Fluids that strongly wet the solid surface possessed the highest ANW* and, hence, the lowest AsN*. In three-fluid media the wetting and spreading behavior of the liquids strongly affects the estimated interfacial areas were predicted from Pc-S data in a similar manner as for two-fluid media. The oil-water and oil-solid interfacial areas were estimated from the oil- water Pc-S curve, while the air-oil interfacial area was obtained from the air-oil Pc-S curve. As many as six interfaces may exist in an oil-wet or fractional wettability medium containing three fluids. The interfacial areas were estimated from three fluid Pc-S relations based on previously developed methods for predicting three-fluid Pc-S relations from two-fluid data.

Last Modified: 7/24/2014
Footer Content Back to Top of Page