DIS TR IB UTION OF PL UTONIUM IN ECOS Y STEMS 379 



incorporation of plutonium by biota of the canyon appears inversely related to clay 

 content, the minimum quantity of clay in soil that is required to sorb plutonium and 

 restrict its movement to biota is unknown. 



Comparative studies of the-biogeochemical behavior of plutonium in ecosystems can 

 facilitate the application of plutonium data to assessments of future environmental 

 impact. Relative distributions and concentrations of plutonium in components of two 

 different ecosystems confirm that the element is not readily incorporated by biota after it 

 has been in the terrestrial environment for 20 to 30 yr. However, in the absence of data 

 over many decades, it is difficult to forecast with certainty the future biological 

 availability of this element. Yet the small inventory in biota and the absence of any 

 evidence of biomagnification indicate limited environmental mobility of the element. 



Currently available indexes of mobility in forest ecosystems 20 to 30 yr after initial 

 contamination suggest that the properties of plutonium have not been modified in a way 

 that would affect its long-term biogeochemical behavior. 



Acknowledgments 



Research for the ORNL study was sponsored by the U. S. Department of Energy under 

 contract with Union Carbide Corporation, Publication No. 1347. The LASL study was 

 funded under contract No. W-7405-Eng.36 between the U. S. Department of Energy and 

 LASL. 



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