Mass Transfer from Non-Aqueous Phase Liquids to the Aqueous Phase in Groundwater Systems
Public Deposited- Last Modified
- February 28, 2019
- Creator
-
Poirier-McNeill, Michelle
- Affiliation: Gillings School of Global Public Health, Department of Environmental Sciences and Engineering
- Abstract
- As immiscible organic contaminants migrate through the subsurface environment, a significant portion of non-aqueous phase liquids (NAPL's) is trapped by capillary forces and remains in the subsurface as immobile blobs or ganglia. Residual saturations of NAPL on the order of 0 - 30 percent have been observed in saturated subsurface systems. The NAPL can partition into the aqueous phase and serve as a long-term source of groundwater contamination. NAPL-aqueous mass transfer rates impact the distribution and the rate of movement of the contaminant within the subsurface. The mass transfer coefficient is a function of many variables including aqueous phase velocity and NAPL-aqueous interfacial area. One-dimensional column experiments were performed in which the NAPL (toluene) is initially at residual saturation while the velocity of the aqueous-phase flow through the porous media (glass beads) is varied. Mass-transfer rates are quantified for the NAPL-aqueous phase system as a function of aqueous-phase velocity, porous media size, and percent NAPL saturation. Aqueous-phase velocities in the range of 0.1 to 35 m/d and NAPL saturations in the range of 2.5 to 21 percent are studied. The results of column experiments are shown in dimensionless form, and criteria are derived that show where the assumption of equilibrium between the NAPL and aqueous phase is appropriate. Initial solubility and mass transfer experiments were performed to determine the effect of humic acid and a cosolvent (ethanol) on NAPL-aqueous solubility and mass transfer characteristics. The results of this research indicate that the rate of NAPL-aqueous interphase mass transfer increases as a function of increasing aqueous phase velocity and percent NAPL saturation. The data indicates that NAPL-aqueous equilibrium is a valid assumption under the experimental conditions addressed in this study.
- Date of publication
- December 1989
- DOI
- Resource type
- Rights statement
- In Copyright
- Advisor
- DiGiano, Francis A.
- Flynn, Michael
- Miller, Cass T.
- Degree
- Master of Science in Environmental Engineering
- Academic concentration
- Water Resources Engineering
- Degree granting institution
- University of North Carolina at Chapel Hill
- Graduation year
- 1989
- Language
- Deposit record
- ad7e9272-7c4f-43e0-afeb-7a5f2526ad76
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- Parents:
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