Air-water interface plays an important role in the transport of many contaminants in the vadose zone. It is also a limiting factor for many processes involve mass or energy transfer between air and water phases in vadose zone. In this research, the gas-phase partitioning tracer method was used to measure air-water interfacial area for eight porous media. The experimental results were used to investigate the influencing factors of the magnitude of air-water interfacial area and the relationship between the air-water interfacial area and water saturation, and capillary pressure. The porous media comprised a series of sands with narrow particle-size ranges, a sand with a wider particle-size distribution, a sandy soil, and a loamy sandy soil. The measurement range was extended to very low water contents in an attempt to determine upper limits for air-water interfacial areas. The measured values were compared to the normalized surface areas of the porous media. The results of the experiments showed that the magnitude of the air-water interfacial areas increased with decreasing water saturation, and approached that of the normalized surface areas. Generally, air-water interfacial areas were larger for media with larger specific surface areas. The change in air-water interfacial area with changing water saturation was less near saturated water contents and greater at smaller values. In addition, the change was greater for the poorly-sorted media than the well-sorted media. An empirical model was developed to describe the observed relationship between air-water interfacial area and water saturation. The coefficients of the model were found to correlate to the porous-medium uniformity coefficient. With this model and associated correlations, only bulk density, specific surface area, and uniformity coefficient are needed to estimate air-water interfacial area for a given water saturation. The model was shown to provide a reasonable description of a literature data set. Potential relationships between air-water interfacial area and capillary pressure under higher water-content conditions are investigated for unsaturated sandy porous media. A conceptual relationship between air-water interfacial area and capillary pressure is hypothesized, and is tested using air-water interfacial area data obtained from gas-phase tracer tests and saturation-pressure data obtained from water-drainage experiments. The results show that the magnitude of the air-water interfacial area increases with increasing capillary pressure, which corresponds to decreasing water content. (Abstract shortened by UMI.)
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/280732 |
| Date | January 2004 |
| Creators | Peng, Sheng |
| Contributors | Brusseau, Mark L. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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