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Convergence of DNAPL source strength functions with site age
1Soil and Water Science Department, University of Florida, Gainesville, Florida 32611, USA.
Environmental Science & Technology
|November 26, 2009
Summary
Site age, defined by mass eluted, simplifies dense nonaqueous phase liquid (DNAPL) dissolution prediction. As DNAPL sites age, contaminant discharge and mass removal rates equalize, allowing accurate predictions using exponential decay models.
Area of Science:
- Environmental Science
- Geochemistry
- Hydrogeology
Background:
- Dense nonaqueous phase liquid (DNAPL) contamination poses significant environmental challenges.
- Predicting DNAPL source zone dissolution is crucial for effective site remediation.
- Source zone architecture influences contaminant mass discharge rates.
Purpose of the Study:
- To investigate temporal changes in DNAPL source zone architecture during dissolution.
- To evaluate the impact of site age on DNAPL dissolution prediction accuracy.
- To determine if simplified dissolution models are applicable for aged DNAPL sites.
Main Methods:
- Laboratory experiments using light transmission visualization to measure DNAPL architecture changes.
- Application of the equilibrium streamtube (EST) model using measured architectures.
- Comparison of predicted dissolution with experimental data at various site ages (0%, 20%, 50%, 90% mass removal).
Main Results:
- DNAPL architecture evolves over time as mass is depleted.
- Fractional reductions in contaminant discharge and mass converge to be equal as sites age.
- Dissolution behavior shifts from log-normal to exponential distribution over time.
Conclusions:
- Site age, quantified by mass eluted, is a key factor in DNAPL dissolution.
- For aged DNAPL sites, simplified exponential decay models can accurately predict future dissolution.
- Detailed source zone characterization may become unnecessary for predicting dissolution at older contaminated sites.
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