A Review of Biokinetic and Biological 

 Transport of Transuranic Radionuclides 

 in the Marine Environment 



T. M. BEASLEY and F. A. CROSS 



Present understanding of the uptake, retention, and loss of transuranic radionuclides by 

 marine biota is limited. Laboratory experiments have demonstrated that for certain 

 species assimilation of plutonium and americium from labeled food is an efficient process 

 and that direct uptake from seawater is important in the bioaccumulation of all 

 transuranic radionuclides studied to date. Organisms appear to play an important role in 

 the vertical transport of these radioelements from the surface layers of the ocean to 

 greater depths. 



A discussion of the biokinetic behavior of transuranic radionuclides in marine organisms 

 should address the rates at which these radioelements are ingested, assimilated, and 

 egested as well as the rates at which they are lost from the organism's tissues over time 

 (e.g., turnover time and biological half-life). In terms of oceanic processes, such 

 information is of little value, however, unless it can be used in predicting the ultimate fate 

 of transuranics released into the marine environment. We have chosen, therefore, to 

 address both these aspects of transuranic behavior and believe that this chapter, along 

 with the chapters by Noshkin (this volume) and by Eyman and Trabalka (this volume), 

 will provide a comprehensive summary of the behavior of transuranics in aquatic 

 ecosystems. 



Background 



By far the greatest amount of information to date dealing with transuranic radionuclides 

 in marine organisms has been confined to the determination of absolute amounts of these 

 radioelements in both whole animals and selected tissues with the subsequent 

 computation of a concentration factor to indicate the degree of biomagnification 

 between the organism and its environment. The use of this approach will be discussed 

 later. 



The review articles by Noshkin (1972), Cherry and Shannon (1974), and Eyman and 

 Trabalka (this volume) describe the general features observed to date in aquatic 

 ecosystems relative to the accumulation of plutonium in aquatic organisms. Although 

 these data do not give information as to the rates of uptake and loss of the transuranics in 

 aquatic organisms, they are useful in clarifying one unfortunate error in terminology that 

 requires rectification. In the truest sense of the word, aquatic organisms do not 

 discriminate against transuranic radionuclides; if they did, the radioelements could not be 

 measured in the organisms deriving these entities from their labeled environments. The 



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