93 range and distribution of 239+240 Pu ratios measured in surface sediments across the lagoon, the ratios found in the three sections of this core are uniquely high; possibly indicating a common source(s) for a majority of the plutonium contamination in the sediment column collected at this station. Only in the 6-8 cm section of this core does the radionuclide ordering sequence differ from that found in surface sediments (Figure 19). section, wnere the relatively low the ordering of sections. eae and 155 2394240 In this pu/?2epy ratio of 175. was found, Eu concentrations is reversed from those in other This order, Pu > Am > Eu, is found in sediments only in the four sections in the bottom of the Bravo Crater core and in the eastern lagoon. Bismuth-207 concentrations were below the limit of detection in most sections of the core. However, in the 0-2 cm section, the concentration of 20735 was at least 4-5 times higher than in any lower section. The concentrations of 60 “Co and 13766 decrease, respectively, to 50% of their largest concentration, at the 9 and 11 cm levels in the core. However, neither of these radionuclides show steadily decreasing concentrations in the upper layers. The concentration of 6% in the 0-2 cm section of the core is significantly lower than its concentration in lower sections. The cencentrations of '37 6. in the 0-2 cm level of the core shows nearly no change with depth. Station B-21 Sediment Core The concentration profiles of all the radionuclides measured in this Sediment core are roughly similar in that the concentrations increase to a maximum at between 5 and 7 cm (except at 3-5 cm for 241 am) and then decrease to 50% of their highest measured concentrations at between 9.5 and 12 cm. The sediments in this core were composed of finely divided material to a depth of 10 cm, after which rapidly increasing proportions of Halimeda began to