Grantee Research Project Results
2000 Progress Report: Dissolution Dynamics of Multiple Component NAPLs In Aqueous and Surfactant/Cosolvent Systems
EPA Grant Number: R827112Title: Dissolution Dynamics of Multiple Component NAPLs In Aqueous and Surfactant/Cosolvent Systems
Investigators: Brusseau, Mark
Institution: University of Arizona
EPA Project Officer: Aja, Hayley
Project Period: September 1, 1998 through August 31, 2001 (Extended to December 20, 2002)
Project Period Covered by this Report: September 1, 1999 through August 31, 2000
Project Amount: $362,453
RFA: Exploratory Research - Physics (1998) RFA Text | Recipients Lists
Research Category: Air , Safer Chemicals , Land and Waste Management
Objective:
The overall goal of the proposed research is to enhance our understanding of the dissolution of non-ideal, multiple-component, nonaqueous phase (immiscible) organic liquids (NAPLs) in subsurface systems. The specific objectives include:1. Investigate the effect of NAPL composition-dependent factors on dissolution of multiple-component NAPLs in groundwater.
2. Investigate the effect of NAPL mass-transfer limitations on dissolution of multiple-component NAPLs in groundwater.
3. Investigate the effect of NAPL composition and mass-transfer limitations on the enhanced dissolution of multiple-component NAPLs caused by solubilization agents.
Progress Summary:
We have made progress along several fronts, as outlined below.1. We have conducted a series of batch experiments to investigate the ideality of dissolution behavior measured for a multiple-component NAPL system containing either water or a surfactant. Specifically, this research investigated the equilibrium solubilization behavior of two- and three-component NAPL mixtures (containing akylbenzenes) in water and biosurfactant solutions. NAPL solubilization was found to be ideal in water (i.e., obeys Raoult's Law), while solubilization in biosurfactant solutions was observed to be nonideal. Specifically, the relatively hydrophobic compounds in the mixture experienced solubility enhancements that were greater than those predicted by ideal enhanced-solubilization theory, while the solubility enhancements for the relatively hydrophilic compounds were less than predicted. The degree of nonideality is shown to be a nonlinear function of the NAPL-phase mole fraction. Empirical relationships based on the NAPL-phase mole fraction and/or micelle-aqueous partition coefficients measured in single-component NAPL systems were developed to estimate values for the multi-component partition coefficients. Empirical relationships that incorporate both the NAPL-phase mole fraction and single-component partition coefficients provided improved estimates for the multi-component partition coefficient.
2. We are completing an initial series of column experiments designed to examine multiple-component NAPL dissolution behavior under dynamic flow conditions. We have completed experiments for the same three-component NAPL system described above, using water and biosurfactant solutions. We will now use another solubilization agent (cyclodextrin).
3. We have conducted a series of column experiments to examine the influence of sorption on low-concentration elution tailing. Such low-concentration elution tailing is often observed at contaminated field sites. A major question of interest is what process (or group of processes) is causing this behavior? Various mass-transfer limitations associated with NAPL dissolution (local-scale mass transfer, heterogeneity-related factors) may contribute to tailing. For multiple-component NAPLs, tailing may be caused, at least in part, by mass-transfer limitations associated with dissolution of multiple-component NAPLs (low NAPL-phase mole fractions, intra-NAPL mass transfer). In addition, rate-limited desorption from the "soil solids" may contribute to observed tailing. Thus, it is important to differentiate the impacts of these various processes. Experiments have been conducted to examine the elution tailing behavior of naphthalene, a compound common to many multiple-component NAPLs. The results indicated that the low-concentration elution tailing can be well simulated using a model that incorporates a continuous distribution of mass-transfer coefficients.
4. We are continuing to develop and apply mathematical models to describe NAPL dissolution and component transport.
Future Activities:
Effective risk assessment and remediation of NAPL-contaminated sites is limited by our current lack of understanding regarding the dissolution behavior of multiple-component NAPLs. The results of our project research are contributing to the resolution of these issues. We plan to continue to pursue the focal points identified above.Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 11 publications | 2 publications in selected types | All 2 journal articles |
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McCray JE, Bai GY, Maier RM, Brusseau ML. Biosurfactant-enhanced solubilization of NAPL mixtures. Journal of Contaminant Hydrology 2001;48(1-2):45-68. |
R827112 (2000) R827112 (2001) R827112 (Final) |
not available |
Supplemental Keywords:
Kgroundwater, soil, chemical transport, risk assessment, chemicals, solvents, NAPL, remediation.EYWORDS, RFA, Ecosystem Protection/Environmental Exposure & Risk, Scientific Discipline, Geographic Area, Water, Waste, Remediation, Restoration, State, Aquatic Ecosystem Restoration, chemical mixtures, Environmental Chemistry, Engineering, Chemistry, & Physics, Groundwater remediation, Physics, cosolvent systems, aquifer remediation design, dissolution dynamics, groundwater contamination, alternative cleanup standards, groundwater recharge, mass transfer limitations, NAPL, aquifer flushing, NAPLs, aquatic ecosystems, mass transfer, soil and groudwater remediation, surfactantsProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.