530 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



deriving the elements either from fallout or from fuel reprocessing wastes. However, 

 Pentreath and Lovett (1976) and Beasley and Fowler (1976b) have presented additional 

 data contrasting the relative amounts of the two isotopes in plaice collected from the 

 Irish Sea and the relative uptake of the two elements by polychaetes exposed to labeled 

 sediments. In plaice (Pleuronectes platessa) there was an indication that ^^'Am was 

 taken up in preference to 239,240p|^j^ although the variable discharge rates of the two 

 isotopes from the Windscale effluent before sampling and the mobility of the fish 

 themselves in the discharge area make a definitive statement regarding differential uptake 

 problematical (Pentreath and Lovett, 1976). For these reasons, and others raised by 

 Fowler and Beasley (1977), accurate estimations of the concentration factors for the fish 

 could not be made. For the polychaetes (Nereis diversicolor), the case is somewhat 

 clearer. Whether exposed to labeled Windscale sediment or to that collected from the 

 Bikini Atoll, uptake of plutonium was greater than that of americium (Beasley and 

 Fowler, 1976b). 



Curium 



At this time (early 1978), we are unable to find any reference to biokinetic experiments, 

 either field or laboratory, which deal specifically with the element curium. Moreover, 

 until proven otherwise, it would not be prudent to extrapolate experimental findings 

 derived from ^'^^Am studies to unequivocally predict curium behavior in marine 

 organisms. We base this statement on the previously published data of Sugihara and 

 Bowen (1962) and Bowen and Sugihara (1965), in which a distinct difference was noted 

 in the behavior of fallout '^''Ce and '^^Pm with respect to their uptake on particulate 

 matter in the oceans. In addition, there continue to be unsettling reports in the literature 

 which suggest a differential behavior between isotopes of the same element due 

 principally to differences in their specific activities or to potential differences due to their 

 existence in different physicochemical forms as a result of "hot-atom chemistry" when 

 formed by decay of a parent radionuclide (Volchok et al., 1975; Hakonson and Johnson, 

 1973; Emery, Klopfer, and Weimer, 1974; Emery and Garland, 1974; Bowen and 

 Livingston, 1975). In the case of plutonium isotopes (Beasley and Fowler, 1976a), 

 polychaetes exposed to labeled sediments from Windscale and Bikini Atoll and to spiked 

 Mediterranean sediments showed no preferential uptake of the isotopes measured (^^^Pu 

 and ^^^'^^"^Pu). There have been no comparable experiments, however, dealing with 

 ^^^Am or ^'*^'^'*'^Cm. The rather large differences in specific activities between ^'*' Am 

 (3.45 Ci/g), ^^^Cm (6.83 x 10^ Ci/g), and to a lesser degree ^'^'^Cm (82.8 Ci/g) still leave 

 open the possibility of differential behavior between the isotopes, particularly if 

 concentration effects become operative at high activity levels, as have been noted 

 between mammahan experiments using ^■^^Pu and 2 3 9,240p^ (Bair et al., 1974). 



Neptunium 



The recent paper by Guary and Fowler (1977) on the biokinetic behavior of ^^^Np in 

 mussels and shrimp appears to be the only published paper on this subject. Direct uptake 

 of ^^"^Np from water by both the mussel (M. galloprovincialis) and the shrimp 

 (L. seticaudata) appears to be much less than that observed from plutonium. Whole-body 

 concentration factors of 15 to 20 for both species were observed after exposure for 3 

 months. Tissue distributions for the mussel followed patterns previously seen for 



