Patterns of Radiocesium in the Sediments of a Stream Channel Contaminated by Production Reactor Effluents

Abstract

Levels of radiocesium contamination of the sediments of the stream bed, delta and associated floodplains of Steel Creek of the AEC Savannah River Plant are among the highest reported for a natural system. Desorption studies have shown that the radiocesium is not tightly held by the sediments. Fine-particle silt and clay sediments averaged 170.47 pCi/g dry weight, with a maximum of 561.96 pCi/g dry weight and were higher in radiocesium content than the coarser sediments which averaged 18.10 pCi/g. Differential distribution of fine and coarse sediments in the stream channel region has resulted in a complex surface mosaic of radiocesium contamination. Samples collected 1 m apart differed in radiocesium content by as much as 190% of their mean. Greater deposition of fine sediments on the delta has given this area the greatest total radiocesium content, although the radiocesium content of the fine sediments, on a per gram basis, was no greater in the delta region than further upstream. Radiocesium was correlated with both available potassium and the organic matter content of the sediments, and over 68% of the total radiocesium was found in the upper 20 cm of sediments.