remove Cs-Ba-137 from the medium. Apparently, Cs-Ba-137 was returned to 

 the medium from lysed cells during the initial growth period. Had the culture 

 been bacteria-free this problem would have been eliminated, Nitzchia continues 

 to slowly accumulate cesium from the medium as long as any is available. 

 6 . The Uptake of Cesium and Strontium by Adsorption 



In the study to determine the accumulation Cesium by G. simplex it was 

 observed that the rate of uptake was greater during the second 24-hour period 

 than it was during the first. This would seem to indicate that even though 

 the experiments with dead and living cells showed the possiblity of adsorption, 

 the role was probably a minor one. While no prior studies had been made of 

 the role of adsorption by phytoplankton cells, yeast cells had been studied. 

 Rothstein and Hayes (1956) reported "That the presence of various fixed 

 anionic groups on the surface of the yeast cell should confer upon it, ion- 

 binding properties similar to those of ion-exchange resins" . They also found 

 that bivalent ions with the exception UOy*" formed a complex with the cellular 

 groups that was of the same order of stability as that of the Mn"*"*" complex 

 and that a large proportion of the cation was bound in less than 2 minutes 

 (tests up to 180 minutes added only 67o more) . They summarized their findings 

 in the following way: (1) binding of exogenous bivalent and univalent cations 

 by the yeast cell was rapid and reversible, obeying a simple mass law equation 

 (2) bivalent cations were bound more firmly than univalent cations, and (3) 

 the binding sites were located on the periphery of the cell. Thus if the 

 cells obey a simples mass-action law in adsorbing cations from the medium 

 the comparatively greater amounts of univalent cations together with the 

 more readily attracted bivalent cations found in sea water would tend to 

 limit the adsorption of cesium. On the other hand there was the possiblity 

 the washing technique prior to filtration was removing any adsorbed cesium, 

 and thus the uptake value would reflect absorption only. Hence, experiments 



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