PLUME-SCALE TESTING OF A SIMPLIFIED METHOD FOR DETECTING TRITIUM CONTAMINATION IN PLANTS AND SOIL Brian J. Andraski 1 , Keith J. Halford 2 , and Robert L. Michel 3 1 U.S. Geological Survey, 333 West Nye Lane, Carson City, NV 89706, andraski@usgs.gov 2 U.S. Geological Survey, 333 West Nye Lane, Carson City, NV 89706, khalford@usgs.gov 3 U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, rlmichel@usgs.gov Cost-effective methods are needed to detect contamination near radioactive-waste and other contaminated sites. Such methods should be capable of providing an early warning of contaminant releases and should be accurate and robust enough for assessing the long-term performance of waste-isolation facilities and remediation measures. Recently, a simplified method for detecting tritium contamination in plants and soil was developed (1). The method includes solar distillation of plant water from foliage, followed by filtration and adsorption of scintillation-interfering constituents on a graphite-based solid-phase-extraction column prior to direct-scintillation counting. The objectives of the in-progress study described here are to (i) test the simplified contamination-detection method for collection and analysis of plume-scale tritium data and (ii) gain insight into tritium migration pathways and processes. Plume-scale testing is being done at the Amargosa Desert Research Site (2) under the auspices of the U.S. Geological Survey Toxic Substances Hydrology Program (3). Creosote bush (Larrea tridentata) samples were collected within a 63-ha area adjacent to a closed low-level radioactive waste facility (Figure 1). The data show elevated plant-water tritium concentrations up to 440 m from the waste facility. The maximum value is 4,890 Bq L −1 . Background values average 2.5 Bq L −1 . “Hot spots” identified by plant data have been verified by soil-water vapor measurements. Figure 1. Plant sample locations and contours of plant-water tritium concentrations.