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Development of a Quantitative Framework for Evaluating Natural Attenuation of 1,1,1-TCA, 1,1-DCA, 1,1-DCE, and 1,4-Dioxane in Groundwater

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[Technical Report, Final Report]

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Monitored natural attenuation MNA has emerged as a preferred remedial option at many sites contaminated with chlorinated solvents because it offers a cost-effective and practical approach for cleanup of solutes in groundwater. However, existing MNA protocols do not include 1,4-dioxane and commonly co-occurring chlorinated solvents like 1,1,1-TCA, 1,1-DCA, and 1,1-DCE. The objectives of this project were to 1 develop a modified model and framework for evaluating natural attenuation of these compounds 2 develop and validate a protocol to directly measure rate constants for natural biodegradation of 1,4-dioxane using 14C-labeled 1,4-dioxane and groundwater from 10 different field sites 3 use the field and lab data to establish if there is consistency between various lines of evidence for 1,4-dioxane attenuation. An evaluation of MNA relies on establishing various lines of evidence, including secondary and tertiary lines of evidence that help demonstrate degradation processes and associated rates that are responsible for the primary line of evidence decreasing concentrations of the target compounds. This project developed a new fate and transport model to easily evaluate historical monitoring data to predict biodegradation rate constants as well as new decision matrices flowcharts that serve as a guided tour on how to interpret potential lines of evidence for MNA. These were then integrated into an existing software platform BioPIC that allows users to access both the model and the decision matrices. Several approaches were also used to generate input data to support and validate the model and framework. First, rate coefficients and lines of evidence for attenuation were calculated andor measured at multiple sites using a focused sampling program at 10 field sites. Second, degradation and the associated rate constants for 1,4-dioxane at these same sites were determined using a 14C-labeled assay developed for this project


Subject Categories:

  • Water Pollution and Control
  • Biochemistry

Distribution Statement:

[A, Approved For Public Release]