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Static and push-pull methods using radon-222 to characterize dense nonaqueous phase liquid saturations.
B M Davis1, J D Istok, L Semprini
1Oregon State University, Department of Civil, Construction and Environmental Engineering, Corvallis, OR 97331, USA. davisbri@engr.orst.edu
Ground Water
|July 23, 2003
Summary
Radon in groundwater effectively tracks dense nonaqueous phase liquid (DNAPL) saturation using static and push-pull tests. This tracer method shows promise for monitoring DNAPL contamination and remediation progress over time.
Area of Science:
- Environmental Science
- Hydrogeology
- Geochemistry
Background:
- Dense nonaqueous phase liquids (DNAPLs) pose significant challenges for groundwater remediation.
- Characterizing DNAPL saturation is crucial for effective site management.
- Naturally occurring radon offers a potential in situ tracer for DNAPL assessment.
Purpose of the Study:
- To investigate the utility of radon as an in situ partitioning tracer for dense nonaqueous phase liquid (DNAPL) saturations.
- To evaluate static and push-pull radon testing methods in a controlled laboratory setting.
- To assess radon's sensitivity to DNAPL saturation changes during contamination and remediation.
Main Methods:
- Laboratory investigation using a physical aquifer model (PAM).
- Static and push-pull radon tests performed before and after trichloroethene (TCE) contamination.
- Alcohol cosolvent flushing and pump-and-treat remediation were simulated.
- Numerical simulations used to estimate radon retardation factors.
Main Results:
- Radon partitioning was observed in both static and push-pull tests after TCE contamination.
- Calculated TCE saturations ranged up to 1.4% (static) and 14.1% (push-pull).
- Post-remediation tests indicated a decrease in DNAPL saturation.
Conclusions:
- Radon is sensitive to spatial and temporal variations in DNAPL saturation.
- The effectiveness of radon tracer methods depends on factors like heterogeneity and test design.
- Further research is needed to address overestimation of retardation factors and optimize test protocols.