584 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



-3335± 518 



-1336 ± 158 



74.5 ±11.8 



1110± 125 

 695 ± 80 



Fig. 2 Activities of 239+2*0 Pu (millicuries per square kilometer) associated with the 

 sediment components in the top 2.5-cm layer of Enewetak lagoon. 



respectively. Isolines were constructed to distinguish regions of the lagoon having similar 

 concentrations. The mean transuranic inventory in the surface layer and the range of 

 concentrations within the defined areas are shown in the two figures. Figures 4 and 5 

 show regions of the surface layer of sediments mXh. similar 2 38py^2 3 9+240pjj ^^^ 

 ^'*^ Am/^^^'''^'*°Pu ratios, respectively. 



The transuranic concentrations in the surface layer of sediments were determined in 

 over 150 ball-milled surface samples of known thickness and in 20 core samples obtained 

 throughout the lagoon. The lagoon was divided into a grid consisting of a series of 6-km^ 

 regions; at least one sediment sample was obtained from each region to provide 

 radiological data for areal distributions. All sediments are composed of different 

 quantities of fine- and coarse-grained carbonate material, shells, coral fragments, and 

 Halimeda debris. No attempt was made in assessing the sediment inventory to distinguish 

 concentration levels in specific sedimentary components. Figures 2 through 5 illustrate 

 the main features of the transuranic distributions in the surface layer of the lagoon 

 sediment. Isolated regions of relatively high concentrations of 2 3 9+2 4 op^ ^^^ evident in 

 some lesser contaminated areas of the lagoon; other small regions of high surface 



