Lewis, G. P.. Savannah River Ecology Laboratory, lewis@srel.edu
Taylor, B. P.. Savannah River Ecology Laboratory, btaylor@srel.edu
Dixon, P. M.. Iowa State University, pdixon@iastate.edu
Pinder, J. E.. Savannah River Ecology Laboratory, pinder@srel.edu
Hinton, T. H.. Savannah River Ecology Laborartory, thinton@srel.edu

 
EVALUATING THE WHOLE-ECOSYSTEM DECLINE OF RADIOCESIUM IN A FORMER REACTOR COOLING RESERVOIR: EVIDENCE FROM SEDIMENTS AND WATER
 
High spatial heterogeneity can complicate assessments of temporal changes in whole-ecosystem pools of nutrients, contaminants, and other substances. For example, radionuclide distributions in aquatic sediments typically exhibit very high spatial heterogeneity. We examined how sampling error from spatial variability affected conclusions about the temporal dynamics of sediment radiocesium (Cs-137) inventories in Pond B, a former reactor cooling reservoir near Aiken, South Carolina, USA. The mean Cs-137 inventories from sediment cores at paired locations in 1984 and 1994 suggested a pond-wide decline of 21% (2.3%/yr) beyond radiodecay. Such a decline was an order of magnitude higher than the estimated hydrologic export of Cs-137 at 0.1-0.4%/yr. However, very high spatial variability among sediment cores resulted in considerable uncertainty about the estimated difference between the two inventories (95% confidence interval: loss rates of -0.8 to +7.8%/yr). Thus, a whole-ecosystem decline in Cs-137 is not conclusively supported by sediment data. However, the inventory of dissolved Cs-137 in the water column of Pond B apparently has declined over time. Cesium-137 concentrations in epilimnetic waters, which were less variable than concentrations in sediments, declined at rates of 2.8 to 8.9%/yr between 1978 and 1998.
 
Day: Tuesday, Feb. 2
Time: 08:45 - 09:00am
Location: Sweeney Center
 
Code: SS19TU0845S