Ecological Effects of Transuranics 

 in the Terrestrial Environment 



F. W. WHICKER 



This chapter explores the ecological effects of transuranium radionuclides in terrestrial 

 environments. No direct studies that relate the level of transuranic contamination to 

 specific changes in structure or function of ecological systems have been carried out. The 

 only alternative approach presently available is to infer such relationships from 

 observations of biota in contaminated environments and models. Advantages and 

 shortcomings of these observations as well as those of the direct experimental approach 

 are discussed. Searches for ecological effects of plutonium contamination in terrestrial 

 ecosystems adjacent to the Rocky Flats plant (Colorado) and at the Nevada Test Site 

 have not positively demonstrated plutonium-induced perturbations. These studies were 

 carried out in areas containing of the order of 10 to 1000 jjiCi ^^'^Pu/m^ in the upper 3 

 cm of soil. Simple calculations suggest that ^^^Pu applications on the order of 1 Ci/m^ 

 may be required to cause significant mortality in plant populations. Models and 

 calculations indicate that over 1 mCi ^^^Pu/m^ would likely be required to produce 

 subacute mortality in mammals. Additional research applicable to ecological effects is 

 suggested. 



To grasp the ecological implications of transuranium elements in the environment, we 

 must understand their chemical, physical, and biological behavior through time. We must 

 also understand the effects on biological systems of these elements when they are 

 dispersed into the environment. Knowledge of the biological effects is particularly 

 lacking. This may seem surprising in view of the large research efforts that have been 

 devoted to the biological effects of plutonium and other transuranics. The lack of 

 quantitative understanding in the area of ecological effects is not so surprising, however, 

 when the complexities of the problem are considered. Such complexities include the 

 environmental behavior of transuranics, which is dependent on the physical and chemical 

 form of the nuclides as well as on the nature of the ecosystem. Of major importance is 

 the dose to certain tissues, but dose distribution is especially complex for relatively 

 insoluble alpha emitters. A high-level application of transuranic may have Uttle radiation 

 effect if energy is not deposited in critical cells. 



Although we know a great deal about the effects of plutonium on experimental 

 mammals (Bair and Thompson, 1974), we know very little about its effects on the other 

 classes of animals that have important functions in natural systems and even less about its 

 effects on plants. Also, very little is known about the general biological effects of the 

 other transuranics. The effects of X- and gamma radiation on major plant and animal 

 phyla have been studied in depth, but the extrapolation of X- and gamma radiation 



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