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Reactive tracer tests to predict dense nonaqueous phase liquid dissolution dynamics in laboratory flow chambers
1Soil and Water Science Department, University of Florida, Gainesville, Florida 32611, USA.
Environmental Science & Technology
|August 30, 2008
Summary
Reactive tracer tests effectively predict contaminant mass and flux reduction in DNAPL-contaminated porous media. This method characterizes subsurface heterogeneities, improving remediation strategies for dense nonaqueous phase liquid (DNAPL) sites.
Area of Science:
- Environmental Science
- Hydrogeology
- Geochemistry
Background:
- Dense nonaqueous phase liquids (DNAPLs) pose significant challenges for groundwater remediation due to their complex behavior in heterogeneous porous media.
- Understanding the relationship between contaminant mass reduction and flux reduction is crucial for assessing the effectiveness of remediation strategies.
- Characterizing DNAPL spatial distribution and aquifer heterogeneities is essential for accurate prediction of contaminant dissolution and transport.
Purpose of the Study:
- To evaluate the relationship between contaminant mass reduction (Rm) and flux reduction (Rj) in DNAPL-contaminated porous media using reactive tracer tests.
- To investigate the utility of tracer tests in characterizing DNAPL spatial distribution heterogeneity and its influence on contaminant dissolution.
- To develop and validate a predictive model for contaminant mass and flux reduction based on tracer test data.
Main Methods:
- Laboratory experiments using flow chambers packed with heterogeneous porous media contaminated with DNAPL.
- Continuous and pulsed cosolvent and surfactant flushing dissolution tests to measure contaminant flux reduction.
- Application of a Lagrangian analytical solution based on the streamtubes concept, independently parametrized using nonreactive and reactive tracer tests.
Main Results:
- Tracer tests successfully characterized aquifer hydrodynamic heterogeneities (nonreactive tracer) and DNAPL spatial distribution heterogeneity (reactive tracer).
- The combination of tracers allowed for the derivation of reactive travel time variance, which was used to predict the Rm-Rj relationship.
- Predictions derived from tracer tests closely matched observed dissolution data, validating the approach.
- Experimental results showed that increased reactive travel time variance led to greater flux reduction for a given partial mass removal.
Conclusions:
- Tracer tests, particularly reactive ones, are effective tools for characterizing DNAPL spatial distribution heterogeneity that governs dissolution behavior.
- The developed method accurately predicts the relationship between contaminant mass and flux reduction, aiding in the assessment of remediation effectiveness.
- Increased reactive travel time variance signifies greater heterogeneity and results in more efficient flux reduction during remediation efforts.
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