632 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



TABLE 1 Estimated Quantities of Annual Production 



of Biomass in U-Pond 



(Weights of existing sediments are also included) 



Estimated annual production 



Weight, kg (dry) Percent of total 



Nonfilamentous algae 

 Filamentous algae 

 Submerged macrophytes 

 Emergent macrophytes 

 Lower invertebrates 

 Resident insects 

 Emergent insects 

 Gastropods 

 Goldfish 



Sediments 



Biota subtotal 



Total 



8.5 X 10' 



5.1 X 10' 

 1.8 X 10" 

 9.4 X 10' 

 6.8 X 10' 



2.2 X 10' 

 1.1 X 10^ 



7.6 X 10' 

 2.1 X 10' 



4.1 X 10" 



3.4 X 10* 



3.4 X 10* 



2.4 X 10"' 



1.5 X 10"' 



5.2 X 10-' 

 2.7 X 10"' 



2.0 X 10"' 



6.3 X 10-" 

 3.2 X 10~' 

 2.2 X 10"' 



6.1 X 10"' 



1.2 X 10" 

 9.9 X 10' 

 1.0 X 10' 



TABLE 2 Means and Confidence Limits (95%) of Plutonium Concentrations in the U-Pond System 



*Sample numbers are shown in parentheses. 



t Lowest observed concentration replaces lower 95% confidence limit since the latter concentration is a negative 

 number. 



including diatoms, Cladophora, Hydrodictyon, and Tetraspora, and the macrophyte 

 Potamogeton. Among these the diatoms and Potamogeton are the principal components 

 where plutonium is accumulated, wliich contain more than 99% of the pond's plutonium 

 inventory accumulated by plants. This suggests that an approximate plutonium inventory 

 for the biota of a similar ecosystem could be rapidly determined by estimating the 

 inventories in only a few populations of flora. 



Of the invertebrate life emergent insects and gastropods have the higliest mean 

 plutonium inventories (Tables 3 and 4). Gastropods show an inventory of 1.8 x lO"* nCi, 

 whereas emergent insects account for 5.1 x 10^ nCi of plutonium. Quantities of 

 plutonium in emergent insects are of particular interest since they provide the only direct 



