Journal
CHEMOSPHERE
Volume 250, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.chemosphere.2020.126305
Keywords
Interfacial partitioning; Interfacial adsorption; Fluid-fluid interfaces
Categories
Funding
- NIEHS Superfund Research Program [P42 ES04940]
- National Natural Science Foundation of China [41902247]
- China Postdoctoral Science Foundation [2018M640284]
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The aqueous-based interfacial tracer method employing miscible-displacement tests is one method available for measuring air-water interfacial areas. One potential limitation to the method is the impact of tracer-induced drainage on the system. The objective of this study was to investigate the efficacy of a low-concentration tracer test method for measuring air-water interfacial area. Tracer concentrations and analytical methods were selected that allowed the use of tracer input concentrations that were below the threshold of tracer-induced drainage. Multiple tracer tests were conducted at different water saturations. Interfacial areas increased from 34.8 to 101 cm(-1) with the decrease in saturation from 0.86 to 0.62. The method produced relatively robust measurements of air-water interfacial area, with coefficients of variation ranging from 6 to 26%. A variably saturated flow and transport model that accounts for the effects of tracer on interfacial tension, and the retention of tracer at the air-water and solid-water interfaces, was used to test for potential tracer-induced drainage. The simulations showed that the use of low tracer-input concentrations eliminated this phenomenon. This is consistent with the measured data for effluent-sample masses, which exhibited minimal change during the tests, and with the observation that the interfacial areas obtained with the low-concentration-tracer method were consistent with values measured with two methods that are not influenced by tracer-induced drainage. These results demonstrate that the low-concentration miscible-displacement tracer test method is an effective approach for measuring air-water interfacial areas in porous media. (C) 2020 Elsevier Ltd. All rights reserved.
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