394 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



Concentration of plutonium in root-vegetable crops reflected contamination by 

 residual soil plutonium. Concentrations ranged from 0.08 to 0.41 pCi/g for whole radish, 

 carrot, and potato samples that had been hand scrubbed before radiochemical analysis. 

 These samples were not examined microscopically for the presence of residual particles, 

 as had been done for sonically cleaned vegetation; yet concentrations of plutonium in 

 storage organs of roots were similar to those in cleaned vegetation. Peeling the skins from 

 potatoes and beets removed most of the residual plutonium. Potato skins averaged 0.53 

 pCi/g, as compared with 0.006 pCi/g for peeled potatoes. This indicates that about 99% 

 of the plutonium was removed by peeling. Beet skins had even greater concentrations of 

 plutonium, 1.3 pCi/g for skins vs. 0.005 pCi/g for peeled beets. Thus peeling the beet 

 removed about 99.5% of the total plutonium in the beet. 



TABLE 5 Plutonium Concentration and Concentration 



Ratio for Soybean Foliage Harvested at Different Stages 



of Growth at Oak Ridge WOC Floodplain 



Number 

 Growth of Total plutonium,* Concentration 



stage samples pCi/g ratiof 



8 weeks 8 (2.0 ± 0.4) x IQ-^* 3 x 10"" 



12 weeks 8 (1.0 ± 0.3) x lO"' 2x10"^ 



16 weeks 8 (1.9 ± 0.4) x lO"' 3 x 10"' 



*Values are means ± 1 standard error. 



f Concentration ratio values are based on a soil concentration of 

 63 + 0.4 (standard error) pCi/g. 



The uptake pattern for the soybean plants at the WOC floodplain is shown in Table 5. 

 The plutonium concentration in the foliage after 8 weeks of growth was only 0.02 pCi/g 

 (dry weight). The plutonium concentration had increased five times (0.10 pCi/g) by the 

 12th week and ten times (0.19 pCi/g) by the 16th week. The fohage biomass was at 

 maximum at around the 16th week. Correspondingly, the CR of the foliage increased by 

 an order of magnitude from the 8th to the 16th week. 



Dose to Man from Ingestion of Plutonium- Contaminated Foodstuff 



The dose to man from ingesting wheat or other foods (Tables 2 and 4) can be estimated 

 from the nomograms in Fig. 2. For example, if a person ate 2 x 10^ g of wheat grain 

 containing 2 fCi Pu/g of dry grain, the 70-yr dose to bone would be ~0.5 mrem. 

 Likewise, if a person ate 2 X 10^ g of peeled Irish potatoes (approximately equivalent to 

 2000 kg of wet potatoes) containing 6 fCi Pu/g (dry weight), the 70-yr dose to bone 

 would be ~1.0 mrem. These doses are low compared with the 130-mrem dose from 

 background radiation (Klement et al., 1972). The basic data used for these calculations 

 came from ICRP publications (International Commission on Radiological Protection, 

 1959; 1972a; 1972b). 



