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Infiltration of PCE in a system containing spatial wettability variations
Denis M O'Carroll1, Scott A Bradford, Linda M Abriola
1Department of Civil and Environmental Engineering, University of Michigan, 181 EWRE, 1351 Beal Avenue, Ann Arbor, MI 48109-2125, USA. denismo@engin.umich.edu
Journal of Contaminant Hydrology
|September 1, 2004
Summary
Spatial wettability variations significantly impact dense non-aqueous phase liquid (DNAPL) migration. Organic-wet sand lenses act as capillary barriers, retaining DNAPL and altering its subsurface flow and entrapment.
Area of Science:
- Environmental Science
- Geoscience
- Hydrogeology
Background:
- Dense non-aqueous phase liquid (DNAPL) contamination poses significant environmental challenges.
- Understanding DNAPL migration and entrapment is crucial for effective remediation strategies.
- Subsurface heterogeneity, particularly wettability variations, can profoundly influence contaminant transport.
Purpose of the Study:
- To investigate and quantify the effect of spatial wettability variations on DNAPL migration and entrapment in saturated porous media.
- To compare experimental findings with multiphase flow simulations incorporating modified capillary pressure and relative permeability relationships.
- To evaluate the performance of different numerical models in predicting DNAPL behavior under heterogeneous wettability conditions.
Main Methods:
- Conducted a two-dimensional infiltration experiment using tetrachloroethylene (PCE) in saturated sands with varying wettability.
- Employed image analysis of digital photographs to estimate PCE mass distributions during infiltration.
- Utilized a multiphase numerical simulator with wettability-modified van Genuchten/Brooks-Corey and Burdine/Mualem relationships to model the experiment.
Main Results:
- Observed that organic-wet sand lenses effectively acted as capillary barriers, retaining PCE and impeding downward migration.
- Image analysis confirmed PCE retention in organic-wet zones, consistent with experimental observations.
- Simulations incorporating wettability modifications and the Burdine relative permeability model qualitatively predicted PCE retention, but the Mualem model failed to capture migration rates.
Conclusions:
- Subsurface wettability variations significantly influence DNAPL migration and entrapment patterns.
- Modified capillary pressure and relative permeability relationships, particularly with the Burdine model, are essential for accurately simulating DNAPL behavior in heterogeneous environments.
- Traditional simulators using water-wet assumptions are inadequate for predicting DNAPL transport under varying wettability conditions.