Mercury source zone identification using soil vapor sampling and analysis

Abstract

Development and demonstration of reliable measurement techniques that can detect and help quantify the nature and extent of elemental mercury (Hg(0)) in the subsurface are needed to reduce uncertainties in the decision-making process and increase the effectiveness of remedial actions. We conducted field tests at the Y-12 National Security Complex in Oak Ridge, Tennessee, USA, to determine if sampling and analysis of Hg(0) vapors in the shallow subsurface (<0.3 m depth) can be used to as an indicator of the location and extent of Hg(0) releases in the subsurface. We constructed a rigid polyvinyl chloride push probe assembly, which was driven into the ground. Soil gas samples were collected through a sealed inner tube of the assembly and were analyzed immediately in the field with a Lumex and/or Jerome Hg(0) analyzer. Time-series sampling showed that Hg vapor concentrations were fairly stable over time, suggesting that the vapor phase Hg(0) was not being depleted and that sampling results were not sensitive to the soil gas purge volume. Hg(0) vapor data collected at over 200 push probe locations at 3 different release sites correlated very well to areas of known Hg(0) contamination. Vertical profiling of Hg(0) vapor concentrations conducted at two locations provided information on the vertical distribution of Hg(0) contamination in the subsurface. We conclude from our studies that soil gas sampling and analysis can be conducted rapidly and inexpensively at large scales to help identify areas contaminated with Hg(0).

Graphical abstract

Keywords

push probe / spill / characterization / mapping / gas

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Acknowledgements

Funding for this project was provided by the US Department of Energy, Office of Environmental Management, Technology Innovation and Development Office as part of the Remediation of Mercury and Industrial Contaminants Applied Field Research Initiative. This work was conducted at Oak Ridge National Laboratory, operated by UT-Battelle for the US Department of Energy under Contract DE-AC05-00OR22725. We would like to thank Steve Field and Terry Cothron of B&W Y-12 for assistance in coordinating the collection of field samples at the Y-12 facility and Marcella Mueller for assisting with figure preparation

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2014 Higher Education Press and Springer-Verlag Berlin Heidelberg