30 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



be particularly pronounced if reducing substances, such as food residues, were present 

 (Sullivan et al., 1979). In contrast, when plutonium is present as Pu(IV) complexes, such 

 as in microbial and plant tissues, preliminary studies indicate that gut absorption is 

 somewhat increased (Sullivan and Garland, 1977; Ballou et al., 1978). This probably 

 occurs because of increased Pu(IV) solubility in the gut and transport across the gut wall 

 as Pu(IV) ion or a low-molecular-weight plutonium complex. For elements that are not 

 readily hydrolyzed in the pH range of the digestive tract, e.g., Np(V), incorporation in 

 plant tissues may reduce gut transport relative to direct absorption from administered 

 solutions (Sullivan, 1979). 



The absorption of transuranic elements other than plutonium, under similar 

 conditions in the gut, may be related to solubility following principles outlined in the 

 previous section. If this is true, gut absorption in the presence of foodstuffs will follow 

 the order Np(V) > Cm(III) ~ Am(III) > Pu(IV) ^ Pu(VI). 



Gut absorption has not been studied in terrestrial invertebrates; thus comparisons 

 with the observations reported for marked uptake in marine invertebrates (vide infra) 

 cannot be made. 



Terrestrial Food Webs. The CR is used to assess the degree of bioaccumulation. Extensive 

 reviews of CR data based on greenhouse and field studies are presented elsewhere 

 (Francis, 1973; Schulz, 1977; Energy Research and Development Administration, 1976; 

 Price, 1973). Table 13 summarizes transuranic-element CR's based on laboratory studies, 

 and Table 14 summarizes those based on field studies. These transuranic elements are 



TABLE 13 Transuranic-Element Concentration Ratios 

 Based on Experimental Studies 



Element Agricultural crops Native plants Reference 



238,239,24opy ^q_,o_^q-3 ^q-s_^q-a FraHcls, 1 97 3 ; Schulz, 1977 i 



Brown, 1976; Price, 1973 

 ^'"Am lO-'-lO' 10-= -10-' Francis, 1973; Schulz, 1977; 



Price, 1973 

 '""•Cm lO-^-lO-' Schieckhise and Cline, this 



volume; Price, 1972; 1973 

 '^'Np 10-' -10-' Schieckhise and Cline, this 



volume; Price, 1972; 1973 



TABLE 14 Transuranic-Element Concentration Ratios 

 Based on Field Studies 



Element Agricultural crops Native plants Native animals* Reference 



'^*Pu 10-''-10° Hakonson and Nyhan, this volume; 



Dalilman, Bondietti, and Eyman, 



1976 

 2 3 9,24opy 10"= -IQ-' 10-" -10° 10-" -10-' Hakonson and Nyhan, this volume; 



Dalilman, Bondietti, and Eyman, 



1976; Little, 1976; Durbin, 1975 

 '"'Am 10-^-10" 10-^ -lO*" Durbin, 1975 



*Based on whole-body burdens. 



