Quantifying PCE and TCE in DNAPL Source Zones: Effects of Sampling Methods Used for Intact Cores at Varied Contaminant Levels and Media Temperatures
Document Type
Article
Publication Date
3-1-2006
Description
An experimental study was completed to assess the impact of sampling methods, contaminant levels, and subsurface temperatures on the quantification of tetrachloroethylene (PCE) and trichloroethylene (TCE) in source zones contaminated by dense non-aqueous phase liquids (DNAPLs). Intact cores of clean aquifer solids (fine-grained uniform sand with low foc) from a DNAPL site in Florida were spiked with neat PCE and TCE to yield concentrations such that DNAPL-phase contamination would be absent or present. Three methods characterized by different levels of media disaggregation and atmospheric exposure (MDE) were used to obtain samples from intact cores, which were at temperatures of 2°C, 20°C, and 38°C. The results of this study demonstrated that sampling of intact cores can yield negative bias, ranging from 0% to 98% or more, in the concentrations of PCE and TCE measured. Larger negative bias was correlated with higher MDE methods, presumably due to elevated volatilization losses during sample collection and containerization. Larger negative bias was also correlated with higher temperatures but only during sampling using higher MDE methods. The results of this study suggest that intact core sampling procedures may or may not lead to erroneous conclusions about a DNAPL source zone. For example, sampling data may lead to a conclusion that a potential source zone has no DNAPL-phase contamination present when in fact it is present, or that remediation has achieved source zone cleanup to a residual concentration goal, when in fact the goal was not met. Conversely, if a remediation goal is to achieve a specified mass depletion level (e.g., 90%), measurement bias may not result in an erroneous conclusion. Further research is planned to examine a wider range of aquifer properties and sampling conditions and to assess the impacts of measurement errors on DNAPL source zone characterization and assessment of remediation performance.
Citation Information
Siegrist, Robert; Lowe, Kathryn S.; Crimi, Michelle L.; and Urynowicz, Michael A.. 2006. Quantifying PCE and TCE in DNAPL Source Zones: Effects of Sampling Methods Used for Intact Cores at Varied Contaminant Levels and Media Temperatures. Ground Water Monitoring and Remediation. Vol.26(2). 114-124. https://doi.org/10.1111/j.1745-6592.2006.00085.x ISSN: 1069-3629