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The effect of multicomponent diffusion on NAPL dissolution from spherical ternary mixtures
Priti P Brahma1, Thomas C Harmon
1Department of Civil and Environmental Engineering, University of California, 5732 Boelter Hall, Los Angeles, CA 90095-1593, USA.
Journal of Contaminant Hydrology
|November 11, 2003
Summary
This study examined non-aqueous phase liquid (NAPL) dissolution, finding intra-NAPL diffusion significantly impacts pore-scale contaminant transport, especially in non-ideal mixtures. At larger scales, diffusion effects are less critical than other factors like flow heterogeneity.
Area of Science:
- Environmental Science
- Geochemistry
- Chemical Engineering
Background:
- Nonaqueous phase liquids (NAPLs) pose significant groundwater contamination challenges.
- Understanding NAPL dissolution is crucial for effective remediation strategies.
Purpose of the Study:
- To compare the contributions of intra-NAPL diffusion, film transfer, and thermodynamic nonideality to NAPL mixture dissolution.
- To evaluate these processes at both pore and intermediate scales.
Main Methods:
- Developed a multicomponent diffusion-based dissolution model incorporating hydrodynamic theory.
- Utilized UNIFAC to estimate activity coefficients for ideal and non-ideal mixtures.
- Employed MT3DMS for three-dimensional groundwater transport simulations.
Main Results:
- Intra-NAPL diffusion significantly impacts pore-scale dissolution, particularly for non-ideal mixtures.
- At intermediate scales, diffusion effects were less significant than mixture uncertainty and hydrodynamic factors.
- Thermodynamic nonideality strongly influenced intra-NAPL diffusion effects.
Conclusions:
- Intra-NAPL diffusion is a key factor in pore-scale NAPL dissolution, influenced by mixture ideality.
- At larger scales, other factors like flow heterogeneity and mixture composition uncertainty dominate dissolution behavior.
- Accurate modeling requires considering both diffusion and thermodynamic properties of NAPL mixtures.