Document Details

Transport and Accumulation of Cesium-137 and Mercury in the Clinch River and Watts Bar Reservoir System
Subject Terms:
Cesium-137, mercury, Hg; contaminants, environment; sediment, samples; waste, Clinch River, Watts Bar
Document Location:
DOE INFORMATION CENTER 1 Way, Oak Ridge, TN 37831; Eva Butler; Phone: 865-241-4780; Toll-Free: 800-382-6938, Option 6; FAX: 865-574-3521; Email:
Document Categories:
Health, Safety and Environment\Waste Management; Health, Safety and Environment\Waste Management
Document Type:
Publication Date:
1992 Jun 30
Declassification Status:
Never classified
Document Pages:
Accession Number:
Document Number(s):
Y-ER01258, ORNL/ER-7
Originating Research Org.:
Martin Marietta Energy Systems, Incorporated
OpenNet Entry Date:
1998 Jun 16
This report is concerning operations and waste disposal activities on the U.S. Department of Energy's Oak Ridge Reservation that have introduced Cesium-137 (Cs-137) and mercury (Hg) into local streams that ultimately drain into the Clinch River and Watts Bar Reservoir system. The highest discharges for both Cs-137 and Hg occurred during the mid-1950's. Measurements of the partitioning of Cs-137 and Hg between dissolved and particulate phases in the reservoir water column indicate that both contaminants have particle-to-water sorption ratios of about 10(5) and are therefore strongly associated with particles in this aquatic system. About 190 surface-sediment grab samples and more than 60 sediment cores were collected in Watts Bar Reservoir to (1) determine the extent of downstream contamination and (2) document particle and particle-associated contaminant accumulation patterns. The vertical distributions of Cs-137 and Hg in these sediment cores are strongly correlated, and both contaminants exhibit a large subsurface peak coincident with their peak discharge histories. A preliminary screening of the contaminants that may contribute to human health and environmental risk showed that these Cs-137 and Hg concentrations do not pose an imminent risk, especially if deep sediments are not disturbed. The comparison between measured and discharged Cs-137 indicates that almost 91 percent of the total Cs-137 released to the Clinch River and Tennessee River system has been retained by accumulation in Watts Bar Reservoir sediments. Using the strong correlation between the vertical distribution of Cs-137 and Hg in sediment cores, it has been estimated that about 76 metric tons of Hg have also accumulated in the sediments of Watts Bar Reservoir. The vertical distribution of Cs-137 and Hg in dated sediment cores was also used to document levels of contamination in the reservoir water column during the past 40 years.

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