Environmental Health - Toxic Substances
Desert Plants Reveal Contaminant Transport Pathways
Map of tritium concentrations in soil-water vapor at a depth of 0.5 meter, Amargosa Desert Research Site (ADRS), Nevada. Soil-water concentrations are inferred from measured plant-water concentrations and predictive relations between plant-water and soil-water-vapor concentrations. Concentrations are given in bequerels per liter (Bq/L). One Bq/L (one decay per second) equals approximately 8.47 tritium units.
USGS scientists have developed a method that uses water collected from plants to map tritium contamination. The plant-based method provides a noninvasive, cost-effective means of mapping subsurface tritium migration in desert areas. The method is sufficiently fast and robust, allowing for repeated sampling with time to determine the evolution of a plume. Compared to conventional methods, the plant-based method affords greater sampling density, which translates to greater accuracy in tracking contaminants. USGS scientists used the method to map tritium plumes at the Amargosa Desert Research Site (ADRS), Nevada. The results showed that tritium moves through dry, coarse-textured layers beneath the root zone, with concurrent upward release to the surface through the root zone.
Phytoremediation, the use of plants to clean up contamination, is often assumed to be limited to contamination in direct contact with plant roots. Application of the plant-based method at the ADRS showed that the remedial effects of vegetation on tritium extend well beneath the root zone. Desert plants serve an important role in the detection and potential remediation of subsurface tritium contamination.
"I just read the article, 'Plant-Based Plume-Scale Mapping of Tritium Contamination in Desert Soils,' and wanted to express my appreciation. This is the first time anyone has mapped subsurface vapor-phase tritium migration using plants, but I doubt it will be the last. The technique that your team worked out, and the quality of the verification that was conducted, virtually ensure that this method will be used again and again. Providing a new technique that saves both time and money without sacrificing data quality is a real contribution, and one which may improve characterization of many environmental sites." -- Steve Rock, National Risk Management Research Laboratory, U.S. Environmental Protection Agency, written communication, 2005.
Andraski, B.J., Stonestrom, D.A., Michel, R.L., Halford, K.J., and Radyk, J.C., 2005, Plant-based plume-scale mapping of tritium contamination in desert soils: Vadose Zone Journal, v. 4, p. 819-827, doi:10.2136/vzj2005.0052.
Andraski, B.J., Halford, K.J., and Michel, R.L., 2004, Plume-scale testing of a simplified method for detecting tritium contamination in plants and soil, in Workshop on Long-term Performance Monitoring of Metals and Radionuclides in the Subsurface, Reston, Virginia, April 21-22, 2004: Florida State University, Tallahassee.
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