Water Interfacial Area Research Articles

Characterizing Gas−Water Interfacial and Bulk-Water Partitioning for Gas-Phase Transport of Organic Contaminants in Unsaturated Porous Media

This study was performed to investigate the impact of interfacial and bulk-water partitioning on the retention and retardation of gas-phase contaminants during transport in unsaturated porous media. Gas-flow experiments were conducted using columns packed with three types of sandy porous media. Moisture contents were 11.9%, 16.0%, and 9.4% for the columns packed with glass beads, silica sand, and aquifer material, respectively. Contaminant retardation was the sum of retention by the gas, aqueous, and solid phases and accumulation at the gas−water interface. The results indicated that 29−73% of total trichloroethene retardation was due to accumulation at the gas−water interface, depending on porous media type. Partitioning into the bulk water accounted for 12−30% of total trichloroethene retardation for the various systems. Given the potential significance of interfacial and bulk-water retention for contaminant transport and remediation, it is important to consider methods for characterizing these processes at the field scale. Gas-phase tracer experi ments using a suite of phase-selective partitioning tracers in combination with nonreactive tracers, as presented herein, may be one viable approach. For example, CO2 was used successfully to measure the bulk-water content of the system, and heptane was used to determine the effective gas−water interfacial area.

Determination of the Air−Water Interfacial Area in Wet “Unsaturated” Porous Media

A method is proposed for determining the area of the air−water interface in wet but unsaturated porous media. The method depends on determining the critical concentration of surfactant necessary to...

Pore scale spatial analysis of two immiscible fluids in porous media

A conceptual model is introduced describing the spatial distribution of two immiscible fluids in the pore space of sphere packings. The model is based on the ideal soil concept of homogeneous arrangement of identical spheres but is generalized to include random packing. It quantitatively analyzes the interfacial area between wetting and nonwetting fluids and between the fluids and the solid spheres, as a function of the saturation degree. These relationships depend on the packing arrangement of the spheres, the sphere radius, and the fluid‐solid contact angle. The model focuses on the region of low saturation of the wetting phase, where the wetting phase is comprised of pendular rings. When the nonwetting phase appears as ganglia, the model assumes single‐chamber ganglia. Three‐dimensional graphical illustrations are provided. Three potential applications are pointed out: (1) to quantify the water‐air interface in the unsaturated zone; (2) to analyze connate water interfacial area in petroleum reservoirs and to assess the effect of surfactants during enhanced oil recovery; and (3) to estimate the interface between groundwater and floating nonaqueous phase liquids above the water table.