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Models and Methods to Evaluate Transport of Drug Delivery Systems Across Cellular Barriers
Published on: October 17, 2013
Tracer method to determine residence time in a permeable reactive barrier
1S.M. Stoller Corporation, Environmental Sciences Laboratory, U.S. Department of Energy Office of Legacy Management, 2597 B 3/4 Road, Grand Junction, CO 81503, USA. timothy.bartlett@gjo.doe.gov
Ground Water
|February 28, 2009
Summary
Radon-222 ((222)Rn) is used as a tracer to measure groundwater residence time in zero-valent iron permeable reactive barriers (PRBs). This method helps assess PRB performance and flow conditions over time.
Area of Science:
- Environmental Science
- Hydrogeology
- Geochemistry
Background:
- Permeable reactive barriers (PRBs) are engineered systems for groundwater remediation.
- Assessing the hydraulic performance and longevity of PRBs is crucial for effective contaminant treatment.
- Groundwater residence time is a key parameter for evaluating PRB efficiency.
Purpose of the Study:
- To present a novel method for evaluating groundwater residence time in zero-valent iron (ZVI) PRBs.
- To utilize radon-222 ((222)Rn) as a radioactive tracer for this assessment.
- To correlate residence time with chemical indicators of PRB performance.
Main Methods:
- Employing radon-222 ((222)Rn) as a naturally occurring radioactive tracer.
- Monitoring the decay of aqueous (222)Rn as groundwater flows through a ZVI PRB.
- Applying the first-order decay equation to determine residence times.
Main Results:
- Groundwater residence times in the ZVI PRB ranged from 80 to 486 hours after 8 years of operation.
- Residence times showed a good correlation with chemical parameters such as pH, Ca, SO(4), and Fe.
- No significant emanation or loss of (222)Rn within the PRB was observed, validating the method.
Conclusions:
- The (222)Rn tracer method provides a reliable means to evaluate groundwater residence time in ZVI PRBs.
- Residence time is a valuable indicator of PRB hydraulic performance and flow heterogeneity.
- The method can be used to estimate groundwater flow rates and monitor PRB conditions over time.
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