252 TRANSURANIC ELEMENTS IN THE ENVIRONMENT 



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Fig. 12 Plutonium-238 concentration on airborne soil as a function of particle diameter 

 at Rocky Flats. 



Concentrations for on-site Hanford experiments are shown in Fig. 14 for collection 

 on filters. Concentrations of ^^^Pu were somewhat greater than those of ^^^Pu. 

 Plutonium concentrations on airborne solids ranged from 10~^ to 10~^ AiCi/g. The only 

 exception was the October 1973 single sample described above, for which the 

 concentration was 6x 10^^ /jCi/g. Otherwise plutonium concentrations on airborne 

 solids around the U-Pond appeared to be nearly independent of time. 



Plutonium concentrations on airborne nonrespirable particles were also determined 

 (Sehmel, 1977a) near the U-Pond on the Hanford reservation for sampling heights from 

 0.3 up to 30 m above ground. Airborne solids were sampled continuously for all wind 

 directions at sites both east and west of the U-Pond. The distance between sampling sites 

 was 480 m. Samples were analyzed for both ^^^Pu and ^^^Pu. Calculated results shown 

 in Fig. 15 are for nonrespirable airborne solids collected within cowls. Results show that 

 plutonium concentrations on nonrespirable airborne solids were approximately one order 

 of magnitude higher east as compared with those west of the U-Pond. This increase is 

 caused by prevailing west winds, which caused resuspension from this low-level 

 hquid-waste disposal area. East of the U-Pond plutonium concentrations on nonrespirable 

 airborne solids tended to be uniform with height up to 30 m. The plume height above 

 30 m is unknown. Plutonium concentrations on nonrespirable airborne solids are within 

 the range shown in Fig. 14 for smaller particles collected on filters. In both cases ^^^Pu 



