University of Washington Abstract CONCENTRATIONS AND REDISTRIBUTION OF PLUTONIUM, ANERICIUM ANO OTHER RADIONUCLIDES ON SEDIMENTS AT BIKINI ATOLL LAGOON by Robert Paul Marshatl The concentrations and distributions of 23942405 2385 Uy 24) Am, 207 Bi Sey, 1376, and 60 Co in the sediments of Bikini atoll lagoon were investigated by radiochemical and radiometric analyses of 33 surface sediment samples and 9 sediment cores collected in 1972. An initial survey of the concentrations of the alpha emitting radionuclides in crater and lagoon sediments was made using a thin source counting technique for measuring total alpha radioactivity. The total alpha values obtained for a Bravo crater sediment were greater (ca. 13%) than the sum of 23942405, 2385, 24la, and the natural radionuclide concentrations measured or estimated, indicating the possibility of other alpha emitting radionuclides which were bomb produced. Sediments collected from a large area of the northern quadrant of the lagoon, from two of the three detonation craters sampled, and from a region southeast of the site of the underwater Baker detonation, typically contained only finely pulverized sediments. Although these sediments contained the highest concentrations of al] radionuclides measured, the areal distribution patterns of each of the radionuclides, except 23942405 and eat a, were dissimilar, and 137 Whereas the highest concentrations of 23942405, 24T an, 155 Eu Cs were measured in surface sediments collected from lagoon stations, 60 the highest concentrations of 238 Pu (19 pCi/g), 207,. Bi (432 pCi/g) and “Co (306 pCi/g) were measured in below surface crater sediment samples. The shape of the major distribution of 2394240 Pu and 241 Am concentra- tions in the lagoon may be described as roughly elliptical. The highest