PLUTONIUM IN ROCKY FLATS FRESHWATER SYSTEMS 651 



100 



il 



LLI 



8i 



^10 



a 



• to 



■u 

 l< 



I LL 

 ' CC 



0.1 



1971 



,1. I I L 



Baseline reservoir 



Period of pond 

 reconstruction 



J L 



1972 



J I \ L 



J L 



1973 



J \ \ l_ 



J L 



100 



< 



CC 



10 



Oi 



u 



D. 



Q- _ 



AMJ J ASONOJFMAMJJASONDJFMAMJ J A 



TIME, months 



0.1 



Fig. 4 Mean plutonium concentrations in surface sediment (pQ/g) and mean plutonium 

 concentrations in unfiltered water (pCi/liter) for baseline reservoir. This sampling station 

 is located where Walnut Creek crosses under Indiana Avenue. 



TABLE 1 Mean-Surface(Top 5 cm)-Sediment ^^^'^'^^Pu 



Concentrations During Preconstruction 



and Postconstruction Periods 



*n = number of sampling periods. 



tMean ± standard error. 



jMean of two samples taken in June 1971. 



ponds that were separate from the holding-pond chain, received httle contaminated plant 

 effluent and contained a larger fraction of nonfilterable plutonium. Less suspended 

 material, including phytoplankton, in ponds Ai and Ci is probably the explanation for 

 this phenomenon. Because of the shallow nature of the pond systems, no apparent 

 vertical distribution of plutonium could be determined. 



