PLUTONIUM CONTENTS OF FIELD CROPS 391 



Soybeans. Data for soybeans from the field and glasshouse are given in Table 2. Total 

 plutonium concentrations in glasshouse-grown plants were an order of magnitude less 

 than those in field-grown plants. The CR for plants grown in the glasshouse was a factor 

 of 10 lower than that for plants grown in the field. The glasshouse plants (whole 

 vegetative plants) were sampled when the bean pods were still green and before the plants 

 started defoliating. The field-grown plants were sampled approximately 1 month before 

 the field was combined, when the plants had the maximum biomass. The plutonium 

 content of the combined grain was two orders of magnitude lower than that of the 

 vegetative parts. 



The bean plants had plutonium concentrations [10~^ pCi/g (dry weight)] and ^■^^Pu 

 percentages similar to those of the wheat straw (whole plants without the grain). 

 Consequently the two crops had similar CR values. However, the soybean grain had 

 slightly lower plutonium contents than the wheat grain. 



Com. Plutonium contents of field- and glasshouse-grown corn are shown in Table 2. So 

 that the extent of interception of fallout particles from the stack by foliage could be 

 determined, corn leaves were sampled from the field when the plants had their maximum 

 biomass. The leaves were sampled from two heights: to 1 m from the ground and 1 to 2 

 m (or 1 m to the top). Plants in the glasshouse were sampled when the ears had matured. 

 The total plutonium content of leaves from glasshouse-grown corn was one order of 

 magnitude lower than that from field-grown corn, and the CR was a factor of 30 lower. 

 Leaves from the 1- to 2-m section of the corn plants had plutonium contents almost a 

 factor of 2 higher than leaves from the lower section (0 to 1 m). This indicates that the 

 upper foliage partially filtered and retained plutonium-bearing particles from atmospheric 

 deposition. 



Shelled grain from the glasshouse had sliglitly lower plutonium concentrations than 

 the field-combined grain (Table 2). However, the CR of the grain from the glasshouse was 

 an order of magnitude lower than that of the field-combined grain. The unsifted 

 combined grain had total plutonium content a factor of 2 higher than that of the sifted. 

 Apparently the extraneous matter separated from the grain contained approximately 50% 

 of the plutonium in the sample. 



Relative Contribution of Root Uptake to Plutonium Contents of Field Crops. A 

 comparison (Table 3) of the total plutonium contents of the vegetated material of the 

 crops grown under field and glasshouse conditions indicates that plutonium contamina- 

 tion of the field crops was primarily external in nature. For wheat and corn samples, 

 approximately 97% of the total contamination was external. For soybeans contribution 

 from root uptake appeared greater than 10%. No plausible explanation can be offered at 

 this time for this discrepancy. 



Forage and Vegetable Crops at WOC Floodplain, Oak Ridge 



Forage and vegetable crops harvested from a field plot located on the contaminated 

 floodplain contained measurable quantities of plutonium. The field experiments were 

 designed to minimize resuspension of dust and subsequent contamination of leaf surfaces 

 by plutonium-contaminated soil from the field experimental plots. Five factors aided this 

 objective: (1) The plastic mulch that covered the plot served as a barrier to the transport 



