3] Pravo thermonuclear device.detonated at Bikini on 1 March 1954. Recently, Nelson and Noshkin (1973) reported the results of a radio‘cuical survey ef the marine envircnment of Eniwetok Atoll. The ordering of atundances of radionuclides found ir Eniwetok Crater deposits was reported as %0sp > 239+240,,, , 155 Eu follows: Ver5, , 125 Sb > 101 Rh > 152 Eu. > 24am > '37eg 5 6%q » 207p; , 2385, They found that all the radionuclides measured were non-uniformly distributed, with significant portions of the lagoon floor shoving concentrations at or below the limits of detection. They computed the rean concentration of several radionuclides in sediments across the lagoon and calculated that 11% of the area of the lagoon was contaminated with 13766 at concentrations higher than the mean 13766 concentration, whereas the percentere was 15-20% for 23942405, 155ey and 24 an, and 20-25% for 207... and 6009, “rey Speculate that in crater depressions at Eniwetok, bottom sediments are probably not subjected to severe scouring or resuspension, and the principal loss of activity from the deposits may only be from slow release to the overlying water and diffusion upwerds where the activities then mix with surface waters and are diluted by advective processes. authors also reported that “since 1964, the concentration levels [of ‘ 125 7 . Scr ‘4 Sty ] 3e6 and 207543 in the [Mike] Crater sediments have . not;dimin- at rates substantially faster than that predicted by radioactive decay." “" rec*\les of sediment cores collected in craters, 207R4 was found to be Oowrtere ~ “7 In surface layers compared to any other radionuclide measured. ere .vs. and . . . : . . Cs were found to increase in concentration with increasing ‘* fe crater sediment and 241 Ay and 155 Eu decreased in concentration we 6 * Aae ee These authors presented convincing evidence that the sediments ‘mn these craters consisted of material redistributed from other oe at the atoll.