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Your Environment. Your Health.

Progress Reports: University of North Carolina-Chapel Hill: Enhanced Remediation of Heterogeneous Subsurface

Superfund Research Program

Enhanced Remediation of Heterogeneous Subsurface

Project Leader: Cass T. Miller
Grant Number: P42ES005948
Funding Period: 1995- 2011

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Progress Reports

Year:   2009  2008  2007  2006  2005  2004  2003  2002  2001  2000  1999  1998  1997  1996  1995 

The focus of this project is on the development of improved methods for the remediation of subsurface systems contaminated with dense nonaqueous phase liquids (DNAPLs), including chlorinated solvents and polycyclic aromatic hydrocarbon (PAH) mixtures. During this past year, the researchers investigated: (1) the behavior of dense brines used in remediation of DNAPLs; and (2) the physicochemical properties of PAH-contaminant sources.

An aim of the researchers is the development of improved methods to remediate contaminated subsurface systems. Part of their strategy is to use dense brines to control the vertical mobilization of DNAPLs after mobilization is facilitated using physicochemical means. They have investigated dense brine dispersion over a wide range of densities and viscosities and advanced a mathematical model to describe this behavior. They also have analyzed field-scale data from a pilot-scale study to determine the role of density and viscosity induced instabilities on brine placement and removal. They found that dense brine layers can be established and efficiently removed and recycled. This attractive behavior results from the establishment and maintenance of sharp density fronts with proper patterns of injection and withdrawal.

The researchers have focused their work on the remediation of former manufactured gas plant (FMGP) tar materials. They have found that these tars are non-Newtonian fluids that exhibit shear thinning behavior and creeping flow, which can persist for very long periods of time. These observations are novel and significant, and the researchers have won two best-poster awards for this work over the last year.

An important and little investigated aspect of FMGP sites is related to chemical composition effects on physicochemical behavior. The researchers have collected several samples from FMGP sites and studied their chemical composition and behavior. They have found that these materials can be DNAPL wetting and that mobilization can be enhanced by altering pH. Their goal is to isolate the chemical mechanisms responsible for altering wettability and exploit these to advance mobilization-based remediation methods.

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