The Migration of Plutonium 



from a Freshwater Ecosystem at Hanford 



RICHARD M. EMERY, DONALD C. KLOPFER, and M. COLLEEN McSHANE 



A reprocessing waste pond at Hanford has been inventoried to determine quantities of 

 Plutonium that have accumulated since its formation in 1944. Expressions of export were 

 developed from these inventory data and from informed assumptions about the vectors 

 that act to mobilize material containing plutonium. This 14-acre pond provides a realistic 

 illustration of the mobility of plutonium in a lentic ecosystem. The ecological behavior of 

 plutonium in this pond is similar to that in other contaminated aquatic systems with 

 widely differing limnological characteristics. Since its creation this pond has received 

 about 1 Ci of ^^^'^^^Pu and ^^^Pu, most of which has been retained by its sediments. 

 Submerged plants, mainly diatoms and Potamogeton, accumulate more than 95% of the 

 plutonium contained in biota. Emergent insects are the only direct biological route of 

 export, mobilizing about 5 X 10^ nCi of plutonium annually, which is also the estimated 

 maximum quantity of the plutonium exported by waterfowl, birds, and mammals 

 collectively. There is no apparent significant export by wind, and it is not likely that 

 plutonium has migrated to the groundwater below U-Pond via percolation. Although this 

 pond has a rapid flushing rate, a eu trophic nutrient supply with a diverse biotic profile, 

 and interacts with an active terrestrial environment, it appears to effectively bind 

 plutonium and prevent it from entering pathways to man and other life. 



The dissemination of plutonium in our environment continues to be a major issue 

 centering around the development and appUcation of nuclear energy. In addressing this 

 problem, investigators have made efforts to inventory the worldwide plutonium burden in 

 terms of fallout and point-source deposition (Electric Power Research Institute, 1976). A 

 number of locations have been identified as having above-background plutonium 

 concentrations, such as weapons-testing sites, sites of accidental releases where plutonium 

 has escaped its container, and sites of controlled releases associated with waste 

 management areas. For some of these areas, such as the Eniwetak and Bikini Atolls and 

 the Mortandad Canyon leading to the Rio Grande, plutonium inventories are being 

 investigated in attempts to estimate quantities that migrate away from these sites over 

 time (Schell and Watters, 1975; Hakonson, Nyhan, and Purtymun, 1976). The export of 

 plutonium away from any contaminated aquatic site has not been sufficiently studied to 

 provide a quantitative example of the environmental mobility of this element. In this 

 regard waste ponds can serve as useful study sites since they often have diverse ecological 

 profiles, receive additions of plutonium over extended periods of time, and have frequent 

 contact with terrestrial forces that can mobilize plutonium. 



Waste ponds likely constitute the most probable and greatest percentage of freshwater 

 environments that become contaminated with plutonium from local sources, whether 



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