TRANS URANIC ELEMENTS AT BIKINI ATOLL 561 



103121 62 104 

 STATIONS 



Kilometers 



Fig. 13 Distribution of 2 ^ 9 ,2 4 o p^ concentrations in deep water (2 m above bottom) at 

 Bikini Atoll. Concentrations in picocuries per cubic meter. 



through the deep passes in the southwestern part of the Atoll. It is here that lagoon water 

 exits into the North Equatorial Current. The pattern for the transport of deep water 

 appears to be that of oceanic water entering the lagoon through the Eneu passage and 

 moving as far as the deep passes at the southwestern part of the lagoon. Oceanic water 

 also either enters througli or over the reef at the northwestern part of the lagoon and 

 dilutes the deep water in this region. As shown in Fig. 6, the higliest 239,240pjj 

 concentrations in sediments are near the northwest reef. The highest 2 3 9,2 4 Op^^ 

 concentrations in the deep water appear to be displaced southward slightly from the 

 higher concentrations that were measured in the sediments and to be transported in an 

 easterly direction. For such a complex water circulation pattern in the lagoon, water must 

 pile up and descend near the western reef and upwell near the eastern reef. This process 

 was identified by Von Arx (1954). Water must flow in opposite directions at the 

 southcentral part of the lagoon. The tongue of oceanic water at the bottom in the 

 southern part of the lagoon has a lower ^^^'^'^^Pu concentration than the surface water 

 that is leaving the lagoon through the deep passes. The same general circulation pattern 

 was inferred from ^ ^ Fe measurements in the same samples except that the source was 

 more concentrated near the northern reef (Schell, 1976). 



The distribution of plutonium in the lagoon water indicates that the near-reef areas 

 contain low concentrations of plutonium; this is probably due to dilution by oceanic 

 water that enters the lagoon from over the reef. Thus the organisms that inhabit the 

 lagoon terrace or seaward reef areas are exposed to very low levels of plutonium even 

 though much higher levels exist inside the lagoon. The predominant source of fish for the 

 returning Marshallese will be those reef fish, which should contain low levels of 

 transuranic radionuclides. The radionuclide levels are probably not much higher than 



