318 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



^^^Pu (0.6/ig/g) in soluble nitrate and DTPA complex forms and with carbon, nitrogen, 

 and water to provide optimal microbial activity. Subsamples ot soil were removed over a 

 95-day aerobic incubation period to determine changes in the numbers of fungi and 

 actinomycetes and relative water solubilities (<0.01 ^m) of the plutonium forms. 

 Comparisons of soU fungal numbers in the presence of ^-'^Pu and ^■'^Pu at common 

 radioactivity levels, but at different mass concentrations, indicated that plutonium 

 toxicity was due to radiation rather than to chemical effects (Fig. 6). Solubility of 



in 

 O 



(J 



Z 

 Z) 



UJ 

 CQ 



D 

 2 



2 - 



1 - 



O Control 



A 239pu_Q-rpA, 10.0 juCi/g 



A 238p^j_QjpA^ 10.0MCi/g 

 _ ■ 239pu (NOg)^, 10.0*iCi/g 



□ 238pu (NOg)^, 10.0MCi/g 



239p^ 



238p^ 



12 16 20 24 



INCUBATION TIME, days 



28 



32 



36 



Fig. 6 Effect of different isotopes of plutonium on survival of soil fungi. [From 

 Schneiderman et al. (1975).] 



plutonium in soil influenced plutonium toxicity to microorganisms with the more-soluble 

 Pu— DTPA forms resulting in the greatest reductions in numbers. Similar studies have not 

 been conducted with other transuranic elements. 



Isolation of Resistant Organisms. Although much information is available regarding 

 organic ligands in soil (previous section), an organometal complex has never been isolated 

 intact from soils. A logical approach to the study of microbial transformations of the 

 transuranic elements is to isolate, from soil, resistant organisms most likely to alter 

 transuranic-element form, study the transformation in vitro, and validate the results in 



