Effect of Heterogeneities on Instability and Fingering of DNAPLS Below the Water Table

EPA Grant Number: R826157
Title: Effect of Heterogeneities on Instability and Fingering of DNAPLS Below the Water Table
Investigators: Neuman, Shlomo P. , Smith, James E.
Institution: University of Arizona
Current Institution: University of Arizona , McMaster University
EPA Project Officer: Lasat, Mitch
Project Period: March 1, 1998 through February 28, 2001
Project Amount: $330,000
RFA: Exploratory Research - Physics (1997) RFA Text |  Recipients Lists
Research Category: Water , Land and Waste Management , Air , Engineering and Environmental Chemistry

Description:

The objective of this research is to investigate analytically, experimentally and computationally the effect of soil heterogeneities on instability and fingering of dense non-aqueous phase liquid (DNAPL) contaminants below the water table in aquifers. A theoretical study of wetting front instability in randomly stratified unsaturated soils by Chen and Neuman (1996) demonstrates that heterogeneities may either reinforce or counteract instability depending on the spatial trend, variance and spatial correlation scale of medium permeabilities. Chen and Neuman considered random fluctuations of permeability about their mean trend to be statistically homogeneous.

Approach:

We propose to launch this project by developing a similar stochastic theory for DNAPLs that propagate downward through a stratified, saturated aquifer, and then to validate it by means of laboratory and computational experiments. In particular, we propose to derive probabilistic criteria for the onset of instability in terms of parameters that describe medium heterogeneity (such as functional forms and coefficients of permeability trend with depth, its variance and spatial covariance), and then to investigate statistically the nature and evolution of corresponding fingers. Once this first phase of our investigation is completed, we propose to extend our theory to randomly heterogeneous media that are not necessarily stratified and to validate aspects of this extended theory by means of laboratory and computational experiments. The laboratory experiments will utilize time domain reflectometry (TDR) for the determination of DNAPL finger distribution and migration. We propose to close our investigation by using a recently developed method of dealing theoretically with multiscale permeability fields (Di Federico and Neuman, 1997a-c) to consider the effect of random fractal permeability distributions on the development of preferential flow paths and their impact on the instability and fingering of DNAPL fronts below the water table.

Expected Results:

The results of this research are expected to provide improved understanding and predictability of DNAPL migration and distribution below the water table, thereby allowing more rational analysis of past and future DNAPL migration, improved delineation of DNAPL source zones, and more cost-effective design of remedial measures for containment or in situ treatment of the source zones.

Publications and Presentations:

Publications have been submitted on this project: View all 11 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 3 journal articles for this project

Supplemental Keywords:

hydrology, groundwater, contamination., Scientific Discipline, Water, Waste, Environmental Chemistry, Physics, Remediation, Engineering, Chemistry, & Physics, Groundwater remediation, environmental monitoring, DNAPL, instability, soil screening, aquifer remediation design, chemical kinetics, soil contaminants, multiscale permeability fields, groundwater contamination, hydrologic site characteristics, stochiometry, time domain reflectrometry, contaminated aquifers

Relevant Websites:

http://www.science.mcmaster.ca/geo/faculty/smith/index.html

Progress and Final Reports:

  • 1998
  • 1999 Progress Report
  • Final Report