CS-137 IN SEDIMENTS OF UTAH LAKES AND RESERVOIRS - EFFECTS OF ELEVATION, SEDIMENTATION-RATE AND FALLOUT HISTORY

Cesium-137 in lentic sediments was measured in 15 impoundments in Utah , two in Oregon, and one in Colorado. Cesium-137 sediment profiles wer e used to investigate areas that may have received additional fallout from aboveground nuclear weapons testing at the Nevada Test Site (NTS) . Factors that affected sedimentation rates and patterns in the impoun dments were explored. Estimated cumulative deposition and mean sedimen tation rates were correlated, and both were inversely related to impou ndment elevation. There was evidence for enhanced fallout Cs-137 depos ition during the period of most intense aboveground testing from 1951 to 1957 at the Nevada Test Site (NTS) at two locations in southwestern Utah. However, our technique for estimating relative NTS fallout gene rally yielded greater within-lake variability than between-lake variab ility. Furthermore, most of the observed Cs-137 deposition in sediment s deposited in the 1951-57 time period could be attributed to global r ather than NTS fallout. Thus, in general, differences between impoundm ents in the relative deposition from NTS fallout could not be statisti cally demonstrated.