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Integration of Flux-Based Methods and Triad Principles for DNAPL Site Management, Part II: Review of Flux Measurement Methods
Citation:
BROOKS, M., L. WOOD, C. G. ENFIELD, M. D. Annable, K. Hatfield, AND P. S. Rao. Integration of Flux-Based Methods and Triad Principles for DNAPL Site Management, Part II: Review of Flux Measurement Methods. Presented at Triad Investigations, New Approach and Innovative Strategies, Amherst, MA, June 10 - 12, 2008.
Impact/Purpose:
Managing dense nonaqueous phase liquid (DNAPL) contaminated sites.
Description:
Managing dense nonaqueous phase liquid (DNAPL) contaminated sites continues to be among the most pressing environmental problems currently faced. One approach that has recently been investigated for use in DNAPL site characterization and remediation is mass flux (mass per unit area per unit time) and mass discharge (mass per unit time) measurements. The use of these measurements can be viewed as an extension of the Triad principles because they serve as collaborative data sets that improve DNAPL site conceptual models, and serve as the basis for a remedial design decision-support framework. Specifically, mass discharge measurements, when collected across one or more control planes located down gradient of the DNAPL source zone provide an integrated measure of the strength of the source. This measurement provides a more robust means to prioritize efforts to remediate contaminated sites, assess a priori the benefits of source zone remediation activity, and optimize remediation efforts based on the spatial distribution of mass flux across the control plane. Methods used to measure mass flux or discharge across control planes can be categorized as traditional approaches, passive flux meters, and pumping methods. The advantages and disadvantages of these methods will be presented. Moreover, results will be presented from sites where changes in contaminant fluxes resulting from aggressive remediation of DNAPL source zone were investigated using passive flux meters and a variation of the Integral Pumping Test. Flux measurements were completed in multiple wells installed along a transect down-gradient of the DNAPL source zones, and perpendicular to the mean groundwater flow direction. Groundwater and contaminant fluxes were measured before and after the source-zone treatment. The measured contaminant fluxes were then integrated across the well transect to estimate contaminant mass discharge from the source zone.