614 TRANS URANIC ELEMENTS IN THE ENVIRONMENT 



TABLE 2 Quotients of Isotopic Ratios in Biota 

 and Potential Source Compartments 



TABLE 3 Concentration Ratios for ^ ^ ^ Pu in Great Lakes 

 Biota, June 1972 to November 1973 (Wet Weight) 



reported for biota of the five Great Lakes, with emphasis on samples from Lake Michigan 

 (Table 3). High CR's in mixed plankton compared with zooplankton are thouglit to be 

 due, at least partially, to plutonium associated with phytoplankton, which predominate in 

 mixed plankton samples. It is further suggested that much of the ^■^^Pu in zooplankton 

 samples is due to phytoplankton in their digestive tracts. Food-chain relationships 

 between most of the species analyzed are mentioned in this chapter and are listed in 

 Table 4. 



