710 TRANS URANIC ELEMENTS IN THE ENVIRONMENT 



valuable for study. Such areas have existed in the past (e.g.. Rocky Flats), but, as a result 

 of public concern, cleanup operations were judged more expedient than biological 

 studies. Cleanup decisions are deserving of greater scientific input because in some cases 

 the operation itself may expose the public to greater risk than leaving the protected 

 material in place. 



Areas that contain notably high levels of naturally occurring alpha emitters seem 

 deserving of further study, particularly if it can be shown how results might be integrated 

 with current knowledge of transuranic behavior and effects. Potentially valuable study 

 areas exist in Brazil, Colorado, Wyoming, and the USSR. 



In terms of theoretical efforts, it seems clear that more generally applicable models 

 are needed. This will require more data from a greater diversity of environments, 

 however, and a much better understanding of basic transport mechanisms. For example, 

 we need to know how climate, vegetation, soil, and other ecosystem attributes affect 

 model parameters that describe such processes as erosion, resuspension, assimilation, and 

 retention. The substantial quantities of data on the environmental behavior of plutonium 

 in the Nevada desert or in Colorado grasslands have only limited applicability to 

 ecosystems in regions of higher precipitation. Resuspension seems to be a particularly 

 critical process affecting the hazard of deposited transuranics, especially in arid regions. 

 As a final point, our knowledge of the effects of pure alpha emitters on plants is far less 

 than our knowledge on animals and is grossly inadequate. Since plants provide stability 

 and the food base of ecosystems, this deficiency should be corrected. 



From a scientific viewpoint, it is clear that additional and redirected research can be 

 justified for transuranium elements in the environment. Social tolerance of environmental 

 contamination with radioactive materials, however, appears to be far lower than 

 biological tolerance. In other words, the level of contamination tliat appears in many 

 cases to prompt cleanup efforts is considerably lower than that which might be expected 

 to elicit obvious biological cliange. Tliis argument might be used against continued 

 funding for environmental transuranic research. If this is to be the case, scientists in the 

 field may need to provide stronger justification for their work in the future. 



Acknowledgments 



Preparation of this manuscript was made possible tlirough support from the U. S. Energy 

 Research and Development Administration under Contract No. EY-76-S-02-1 156 with 

 Colorado State University. I am indebted to a number of colleagues who assisted in the 

 development of the manuscript. In particular, I wish to cite the exceptional help of A. W. 

 Alldredge, R. O. Gilbert, D. C. Hunt, C. A. Little, W. A. Rlioads, R. C. Thompson, T. F. 

 Winsor, and M. R. Zelle. 



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