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Estimating Persistent Mass Flux of Volatile Contaminants from the Vadose Zone to Ground Water
Author(s) -
Truex M.J.,
Oostrom M.,
Brusseau M.L.
Publication year - 2009
Publication title -
groundwater monitoring and remediation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 47
eISSN - 1745-6592
pISSN - 1069-3629
DOI - 10.1111/j.1745-6592.2009.01236.x
Subject(s) - vadose zone , water table , groundwater , soil vapor extraction , environmental remediation , capillary fringe , groundwater recharge , environmental science , hydrology (agriculture) , flux (metallurgy) , plume , contamination , soil science , geology , aquifer , chemistry , geotechnical engineering , meteorology , geography , ecology , organic chemistry , biology
Contaminants may persist for long time periods within low permeability portions of the vadose zone where they cannot be effectively treated and are a potential continuing source of contamination to ground water. Setting appropriate vadose zone remediation goals typically requires evaluating these persistent sources in terms of their impact on meeting ground water remediation goals. Estimating the impact on ground water can be challenging at sites with low aqueous recharge rates where vapor‐phase movement is the dominant transport process in the vadose zone. Existing one‐dimensional approaches for simulating transport of volatile contaminants in the vadose zone are considered and compared to a new flux‐continuity‐based assessment of vapor‐phase contaminant movement from the vadose zone to the ground water. The flux‐continuity‐based assessment demonstrates that the ability of the ground water to move contaminant away from the water table controls the vapor‐phase mass flux from the vadose zone across the water table. Limitations of these approaches are then discussed with respect to the required assumptions and the need to incorporate three‐dimensional processes when evaluating vapor‐phase transport from the vadose zone to the ground water. The carbon tetrachloride plume at the U.S. Department of Energy Hanford Site is used as the example site where persistent vadose zone contamination needs to be considered in the context of ground water remediation.