Dissolved Humic Substances in Enhanced Dissolution of DNAPLs

EPA Grant Number: R826650
Title: Dissolved Humic Substances in Enhanced Dissolution of DNAPLs
Investigators: Johnson, William P.
Institution: University of Utah
EPA Project Officer: Lasat, Mitch
Project Period: September 1, 1998 through August 31, 2001
Project Amount: $285,595
RFA: Exploratory Research - Environmental Chemistry (1998) RFA Text |  Recipients Lists
Research Category: Sustainability , Land and Waste Management , Air , Engineering and Environmental Chemistry

Description:

Research investigating the use of solubilizing agents to enhance the dissolution of dense non-aqueous phase liquids (DNAPLs), has been dominated by examination of surfactants. Dissolved humic substances (DHS) are herein hypothesized to be advantageous solubilizing agents in cases where the DNAPL is creosote or coal tar (comprised of polycyclic aromatic hydrocarbons, PAH), the advantage arising from the lack of a critical minimum DHS concentration to initiate solubilization. DHS may also show an apparent lesser tendency to depress DNAPL-water interfacial tension (IFT) relative to surfactants. Since depression of DNAPL-water IFT may lead to DNAPL mobilization, DHS may be advantageous when mobilization is undesired. This proposal seeks to examine terrestrial DHS for the above properties. It is also proposed to examine the sorption behavior of DHS relative to surfactants, since sorption loss affects solubilizing ability and economy of remediation.

Approach:

The proposed project will utilize batch experiments to examine the equilibrium solubilizing capacity of terrestrial DHS for various DNAPL compounds and mixtures, as well as the equilibrium sorption behavior of DHS on various subsurface materials, for comparison to surfactants. Column experiments will be run to determine the kinetics of DHS sorption and to examine the kinetics of enhanced dissolution of various DNAPL mixtures, for comparison to surfactants. High and low DHS concentrations will be examined to determine the effect of DHS concentration on solubilization kinetics. Enhanced dissolution experiments will be modeled using a lumped mass transfer parameter to allow comparison to published results for surfactants. DNAPL-water IFT will be measured in the presence of high concentrations of DHS, to compare tendency to depress DNAPL-water IFT to that of surfactants.

Expected Results:

The proposed investigation will determine the conditions under which terrestrial DHS are superior to surfactants in solubilization of DNAPLs, that is, whether terrestrial DHS offer an effective alternative to surfactants as a solubilization agent in cases where the DNAPL of concern is comprised mainly of PAH compounds, in cases where DNAPL mobilization is undesired, and in cases where sorption of the solubilizing agent to the stationary phase must be minimized. This information directly affects risk management strategies for DNAPLs. The investigation will also determine whether terrestrial DHS show a stronger affinity for polycyclic aromatic hydrocarbons relative to other hydrophobic organic compounds, as has been observed for aquatic DHS. This is fundamental information which would increase understanding of the mechanisms governing partitioning of hydrophobic compounds to humic substances.

Publications and Presentations:

Publications have been submitted on this project: View all 8 publications for this project

Journal Articles:

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

Supplemental Keywords:

groundwater, chemical transport, exposure, risk, environmental chemistry, analytical, modeling, restoration, clean up, remediation, innovative technologies, dissolution., RFA, Scientific Discipline, Air, Toxics, Waste, Remediation, Environmental Chemistry, Chemistry, HAPS, chemical mixtures, Groundwater remediation, Engineering, Chemistry, & Physics, fate and transport, DNAPL, hydrocarbon, exposure, chemical composition, chemical transport modeling, PAH, Cresols/Cresylic acid (isomers and mixture), chemical kinetics, groundwater contamination, surfactants, creosote

Progress and Final Reports:

  • 1999
  • 2000 Progress Report
  • Final Report