TRANSURANIC RADIONUCLIDES IN ENEWETAK LAGOON 591 



17E 



I 



239 + 240 



Pu 



241 



Am 



Eastern 

 lip 



16E 15E 14E 



CRATER STATION IDENTIFICATION 



Fig. 6 Vertical and areal distributions of ^ ^ '"""^ ''"Pu and ^ " ' Am activities in sediments 

 in Mike and Koa craters. 



of transuranics detected in this relatively small region of the lagoon where the 

 distributions are expected to be more uniform are but examples of the complex patterns 

 in the lagoon. 



Halimeda, shells, coral, and foraininifera fragments were sorted from the coarse 

 fraction of several sediment samples by hand. Table 3 shows the 239+240p|j concentra- 

 tions associated with each component in the surface layer from two locations in 

 Enewetak lagoon and at various depths in a core from Bikini lagoon. The ^^' ^"^^Pu 

 concentration associated with Halimeda fragments at station 40C only slightly exceeds 

 that in fragments from station 3D. The concentrations associated with the separated 

 foraminifera and coral fragments from station 40C are, however, at least 2.5 times higher 

 than those associated with their respective components at station 3D. The distribution of 

 2 39 2 40pjj j^ different among components in the sediment from different regions of the 

 lagoon. The fine fraction at these locations contained the highest concentration of 

 2 39 +2 40 p^^ To within our analytical precision, the ^^^Pu/^^^'^^'^^Pu concentration 

 ratio is identical in the components from both stations. 



In the sediment column from Bikini station B3, 239+240p^ ^^^ associated with all 

 components that were separated. At all depths in the sediment column, the highest 

 concentration of 2 3 9+2 4 op^ -^^ ^.j^^ coarse components was associated with Halimeda 

 fragments. Sedimentation of labeled material to the lagoon occurs at a rate that is too 

 slow to account for the buried activities below a few millimeters in the sediment column. 

 Although the age of the Halimeda fragments, coral, and other components at depths 

 greater than a few centimeters must tlierefore predate the test years, 2 3 9+2 4 Op^ j^ 

 associated with these components. 



