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Laboratory Testing of a Novel Unbalanced Recirculation Method for Field Matrix (Back) Diffusion Quantification


EMSL Project ID
48553

Abstract

There is a distinct need to develop and validate field-scale methods for estimating matrix (back) diffusion because degradation and diffusion of contaminants at interfaces of low- and high-permeability layers is important in quantifying and predicting plume behavior and designing remediation. This is especially important in a variety of hydrogeologic settings such as heterogeneous unconsolidated media and sedimentary fractured rock. Field methods for quantifying matrix diffusion of contaminants from low-permeability layers face difficulties associated with measuring this process in the presence of other factors contributing to observed contaminant concentrations in an unconstrained (“open”) field system.

The objective of this work is to test, using intermediate-scale flow cells, a novel method for quantifying matrix diffusion. The method uses an unbalanced recirculation cell approach in which the extraction rate is lower than the injection rate, such that the extracted contaminant mass originates from low-permeability zones through matrix diffusion. This method would provide an integrated measure of matrix diffusion over the interrogated volume quantified using modified pumping test methods, similar to those originally developed for evaluating contaminant mass discharge of contaminants, but incorporating a recirculation approach to measure mass discharge out of low-permeability zones into high-permeability zones. Successful implementation in the EMSL laboratory is a project requirement that needs to be met before application in the field.

Project Details

Project type
Exploratory Research
Start Date
2014-11-11
End Date
2015-09-30
Status
Closed

Team

Principal Investigator

Mart Oostrom
Institution
Pacific Northwest National Laboratory

Team Members

Emily AE Leist
Institution
Pacific Northwest National Laboratory

Michael Truex
Institution
Pacific Northwest National Laboratory