MIGRATION OF PLUTONIUM FROM FRESHWATER ECOSYSTEMS 641 



INVENTORY 



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Fig. 5 Plutonium in ecological compartments of U-Pond compared with estimated 

 quantities that are exported from the pond annually. Export of plutonium by 

 percolation or wind does not appear to be significant. 



plutonium annually exported by waterfowl range from 4 x 10^ to 4 x 10^ nCi, with a 

 mean annual export of 5 x 10^ nCi of plutonium (Fig. 5). Other birds appear to export 

 about 1 X 10^ nCi of plutonium each year, with a maximum of 2 x 10^ nCi (Fig. 5). 

 These export quantities are about six orders of magnitude lower than the total inventory 

 of plutonium in the pond. Mammals are estimated to export a maximum of 3 x 10^ nCi 

 of plutonium from the pond (Fig. 5) annually, which is at least five orders of magnitude 

 lower than the minimum total plutonium inventory of the pond. There is no apparent 

 significant export of plutonium from the pond via wind or percolation. 



In conclusion, U-Pond has been exposed to plutonium longer than any other aquatic 

 system and has received about 1 Ci of ^^^'^'*°Pu and ^^^I*u. This 14-acre pond provides 

 a realistic illustration of the mobility of plutonium in a lentic or nonflowing ecosystem. 

 Although this pond has a rapid flushing rate, is highly enriched with plant nutrients, is 

 ecologically well established with a natural complexity of populations and diversity of 

 communities, and has continuous interaction with associated terrestrial life, it appears to 

 effectively bind the plutonium discharged into it and prevent it from moving significantly 

 into routes leading to man and other remote life. Fur^ermore, the environmental 

 behavior of plutonium in U-Pond appears to be quite similar to that of other aquatic 



