1 ->-J 



4. The Accumulation of Cs-Ba ' by Various Phytoplankton 



The uptake studies using Cs-Ba -'' were conducted in much the same 



manner as those used for the strontium-yttrium studies except that the 



cells were washed free of the isotope by an elaborate washing process 



before filtration. Preliminary studies with the unialgal cultures showed 



that K. rotundata failed to accumulate cesium so this organism was not used 



in the study. G, s imp lex and Nitzchia speriata were the unialgal cultures 



used. Triplicate samples from duplicate flasks were withdrawn each 24 hours 



after the initial exposure to the radioisotope up to 96 hours. The results 



of this study for G, simplex are shown in table 7. 



Table ?. The accumulation rate of Cs-Ba''--^^ by G. simp lex 

 (medium: 2.5 x 104 cpm/ml) 



The 48-hour concentration factor for G. simplex was found to be 13.8 + 

 16%. The rate of uptake was greater during the second 24-hour period than 

 it was during the first. During the first 24 hours to cells had accumulated 

 only about 2.5 times that of the medium while this increased to almost 14 

 during the second 24 hour period. At the end of 72 hours however, the rate 

 of accumulation again decreased to a factor of 9.4. This increase in rate 

 of accumulation followed by a decrease is probably due to the culture being 



18- 



