HR: 11:40h
AN: H42B-05    [Abstracts]
TI: Surrogate Indicators of Radionuclide Migration at the Amargosa Desert Research Site, Nye County, Nevada
AU: * Stonestrom, D A
EM: dastones@usgs.gov
AF: USGS, 345 Middlefield Rd., MS-421, Menlo Park, CA 94025-3591 United States
AU: Andraski, B J
EM: andraski@usgs.gov
AF: USGS, 333 W. Nye Ln., Suite 203, Carson City, NV 89706-0807 United States
AU: Baker, R J
EM: rbaker@usgs.gov
AF: USGS, 810 Bear Tavern Rd., Suite 206, West Trenton, NJ 08628-1022 United States
AU: Luo, W
EM: wentai@ebs.ogi.edu
AF: Oregon Health & Science Univ., 20000 NW Walker Rd., Beaverton, OR 97006-8921 United States
AU: Michel, R L
EM: rlmichel@usgs.gov
AF: USGS, 345 Middlefield Rd., MS-434, Menlo Park, CA 94025-3591 United States
AB: Contaminant-transport processes are being investigated at the U.S. Geological Survey's Amargosa Desert Research Site (ADRS), adjacent to the Nation's first commercial disposal facility for low-level radioactive waste. Gases containing tritium and radiocarbon are migrating through a 110-m thick unsaturated zone from unlined trenches that received waste from 1962 to 1992. Information on plume dynamics comes from an array of shallow (<2 m) and two vertical arrays of deep (5-109 m) gas-sampling ports, plus ground-water monitoring wells. Migration is dominated by lateral transport in the upper 50 m of sediments. Radiological analyses require ex-situ wet-chemical techniques, because in-situ sensors for the radionuclides of interest do not exist. As at other LLRW-disposal facilities, radionuclides at the ADRS are mixed with varying amounts of volatile organic compounds (VOCs) and other substances. Halogenated-methanes, -ethanes, and -ethenes dominate the complex mixture of VOCs migrating from the disposal area. These compounds and their degradates provide a distinctive "fingerprint" of contamination originating from low-level radioactive waste. Carbon-dioxide and VOC anomalies provide indicator proxies for radionuclide contamination. Spatial and temporal patterns of co-disposed and byproduct constituents provide field-scale information about physical and biochemical processes involved in transport. Processes include reduction and biorespiration within trenches, and largely non-reactive, barometrically dispersed diffusion away from trenches.
DE: 0400 Biogeosciences
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2005 Joint Assembly