7/6 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



Atomic Energy Agency, 1976) and reviews some recent experimental data on the effects 

 of plutonium on aquatic organisms. 



Dose Rates from Transuraiiics and Natural Radionuclides in Natural Waters 



A few recent papers have dealt with dose rates received by aquatic organisms exposed to 

 plutonium in natural waters, and they are compared here with dose rates from the natural 

 radionuclide ' ' *^Po. 



Till, Kaye, and Trebalka (1976), Till and Franks (1977), and Till (1978) have 

 estimated the dose rate during embryogenesis for six species of marine and freshwater 

 fishes exposed to plutonium in a variety of natural waters (northeast Irish Sea; Wliite Oak 

 Lake, Oak Ridge National Laboratory; U-Pond, Hanford; Enewetak lagoon; and Lake 

 Michigan). They estimated that the dose rates ranged from 7 X 10^^ /irad of plutonium 

 per hour for plaice (Pleuronectes platessa) eggs exposed at 1 pCi of plutonium per liter of 

 water in the Irish Sea to 3 X 10~^ /Jrad/hr for carp (Cyprinus carpio) eggs exposed at 

 1 X 10"^ pCi/liter in Lake Michigan. These dose rates are less than those from the 

 natural radionuchdes ^ ' °Pb and ^' °Po (Woodhead et al., 1976). 



Hetherington et al. (1976) estimated the dose rates to the embryos of plaice, adult 

 plaice, and other organisms from the northeast Irish Sea where plutonium concentrations 

 in water are of the order of 1 pCi/Hter and the concentrations of 238,2 39,240p^ -^^ ^^ 

 sediment out to 10 km from the discharge point are of the order of 40 pCi of plutonium 

 per gram of sediment. The ratio of ^'^^ Am to 2 3 8, 2 3 9,2 4 op^^ tj-^^ ^-^^^^ stations had a 

 mean value of 1.3 ± 0.2. The estimated dose rates to the developing plaice eggs that had 

 been exposed to 1 pCi/Uter were in the range of 0.09 to 0.47 Atrad/hr, which is somewhat 

 less than the 0.7 /urad/hr from natural '^^K and less than tlie dose received by 

 zooplankton from ^^^Po (Woodhead et al., 1976). Dose rates from ^^^Pu, "^'^"^^Pu, 

 and ^'^^ Am have also been estimated for young (Group III) plaice, crab (Cancer pagiims), 

 and mussels (Mytilus edulis). The total dose rates (Table 1) are of the same order as those 

 from the natural background from ^ ' °Po except for the soft tissues of mussels and gills 

 of crab. In these exceptions there is a possibility that the tissues were contaminated by 

 sediment. 



Effects Studies 



There is a paucity of data in the literature on the effects of transuranics on aquatic biota. 

 Studies of the effects of ^^'^Pu on the eggs of carp have been reported by Auerbach, 

 Nelson, and Struxness (1974). No observable effects were seen either in tlie rate of 

 hatching or in the frequency of abnormalities when eggs were exposed to concentrations 

 ranging from 5x10^ to 5 x 10^ pCi/liter, which is many orders of magnitude above 

 concentrations known to exist in the natural environment. Till, Kaye, and Trebalka (1976) 

 have reported on the doses that produced effects on hatching, survival, and abnormalities 

 in carp and fathead minnow ('P/>??£'p/za/£'spn)«?^/flSy' eggs (Table 2). Accumulated doses that, 

 over the period of embryogenesis, first produced a significant effect on hatching and 

 survival were in excess of 2000 rad for both species. Abnormahties were first produced 

 when the accumulated dose exceeded 750 rad. These doses would be significantly greater 

 in dose-equivalent units, where for alpha radioactivity the dose (in rad) is multiplied by a 

 quality factor. These data indicate that these fish eggs are relatively insensitive to the 

 effects of alpha radiation from ^^^Pu. The data also infer that concentrations of 1 ^Ci of 



