12 di 2415, 2394240, activity ratio was 11,7 and the 24155, 239py ratio was 21.0 + 1.1 (No 75). Recent values of the 2415, 239 Pu ratio in soil samples from Bikini and Eneu Islands and in Bikini island vegetation averaged 22.0 + 3.3 (Mo 76) as of 1 January 1975. Bikini and Eneu Islands and the sedimentary environment from which the coral was obtained were contaminated principally with radioactive debris from the 1954 Bravo event. The good agreement between the ratios determined in the terrestrial and marine samples indicates a lack of discrimination between 241 Pu and 239 Pu isotopes in processes in these environments, No other americium isotopes were detected In the aquatic environment of either Enewetak or Bikini. Curium . 242 No strenuous effort has been made to obtain an inventory of Cm Correcting the 241pu in the November 1972 coral growth section for decay to 1 January 1975 yields a 244 5y 239py ratio of 18,9 + 1.1. location in the lagoon. or 244 “'"Cm in Enewetak by alpha spectrometry, . Curdum activities were separated and measured in several lagoon water samples; P82 on activities were less than 0.2 (Ci/l. No 42a or 244 was detected in sediment samples from the Bravo Crater at Bikinl Atoll (Be76). Higher Transuranics No information is available to this authors knowledge on either Berkelium or Californium in marine sarples from Enewetak or Bikini. Bikini and Enewetak have very different isotopic ratios and therefore different inventories of plutonium isotopes. The amount of 2415, in the environment regulates the projected inventory of 241 am through growth and beta decay of the parent radionuclide. The amount of 24d that will be generated at Bikini from 24ley decay will exceed the amount The distributions of 2394240), and 240 activities measured in December 1972 and expressed as mC4 [ler in the 2.5-cm-thick surface layer of sediment from the lagoon floor are shown in Tigs. 2 and 3. produced by this source at Enewetak. Isolines were constructed to distinguish regions of the lapoon having similar Americium The distribution of 2Als, is also widespread in the aquatic environment of the Atoll. Although the highest concentrations of plutonium and americium are in the same areas of the lagoon at Enewetak, the two transuranics are distributed differently. The 241, 23942405, ratio in sediments collected during 1972 from the lagoon ranged from 0.06 to 0.93, TRANSURANICS IN THE BENTHIC ENVIRONMFNT OF ENLWETAK ATOLL Surface Sediment Distributions and Inventories Significant errors therefore can be introduced if one transuranic is used to predict the levels of others at any given concentrations. The mean transuranic inventory in the surface layer and the range of concentrations within the defined areas are shown in the two figures. with similar Figs. 4 and 5 show regions of the surface sediment layer 238, 2394240, and 241ea OP2 AG Pu ratios. The transuranic concentrations in the surface layer sediments were determined in over 150 ball-milled surface samples of known thickness and in 20 core samples obtained throughout the lagoon. we The lagoon was