PLUTONIUM IN ROCKY FLATS FRESHWATER SYSTEMS 655 



TABLE 6 Concentration of ^ ^ ^ '^ ^ ° Pu in Fish Inhabiting 

 Rocky Flats Environs 



*Number of composite fish samples analyzed (5 fish/composite), 

 f Mean ± standard error. 



Crayfish 



Crayfish, a large invertebrate common to the pond system, showed CR's relative to 

 unfiltered water in the range of 320 to 1290 with a mean value of 830 (Table 5). These 

 values are similar to those found in other studies. Seventy -seven percent of the plutonium 

 in crayfish was associated with the exoskeleton, even though the crayfish were scrubbed 

 extensively. The benthic origin of these organisms probably explains the higli plutonium 

 concentrations associated with the exoskeleton. 



Fish 



Fish flesh and bone from ponds A and C and reservoirs were never above MDA (0.30 

 d/min per sample) even when several samples were composited (Table 6). Whole fish, 

 however, contained measurable amounts of plutonium in the gut contents, the head, and 

 the outer skin. This suggests that plutonium is being discriminated against at this trophic 

 level. 



Flora 



No true aquatic vascular plants and relatively few emergent species existed in the pond 

 systems at Rocky Flats. Bulrush (Junciis balticus) rooted sporadically within the ponds, 

 and cattail (Tvpha latifolia) frequently grew with its roots submerged. Dock (Rumex 

 crispus) was abundant in the riparian area. Concentration ratios for plants associated 

 closely with pond sediments confirmed the observation that the transfer of plutonium 

 from sediments to aerial portions through roots is higher than that previously reported in 

 laboratory experiments (Romney, Mork, and Larson, 1970) (Table 7). Concentration 

 ratios were in the 10~- to 10~* range. This could suggest that the plutonium associated 



