ASSOCIATIONS OF Pu AND OTHER ACTINIDES IN SOILS 155 



containment the plutonium-bearing oil was filtered to remove the large particles (Navratil 

 and Baldwin, 1977). The plutonium would not oxidize in the oil; however, once the 

 plutonium was in the soil and the protective oil was leached, the oxide form would 

 predominate. With room-temperature extraction using 8M nitric acid, the RF samples 

 showed 15 to 20% dissolution; this can be compared with the 10 to 15% observed in the 

 NTS samples. Tliis suggests that both RF and NTS plutonium are similar in character; the 

 higher solubility of the RF vs. the NTS samples in the mineral acid may be ascribed to the 

 smaller size of the plutonium or to the lower temperature of ignition of the RF samples. 



Mound Laboratory. Contamination in the canal at ML occurred in 1969 through 

 sedimentation of eroded soil particles contaminated with ^^*Pu. Initially, the plutonium 

 was in an acidic solution as plutonium nitrate. During transfer the pipeline ruptured and 

 the plutonium was sorbed on soil particles. The sorbed plutonium was eroded during 

 cleanup operations by intense rains (Rogers, 1975). Thus, unlike the metallic origin of the 

 plutonium at the NTS and RF locations, the ML contamination was originally in a soluble 

 form. That the character of the plutonium differed from the NTS and RF samples is 

 exemphfied by the higher solubility (80 to 85%) in cold 8M nitric acid. The 

 contamination in the canal should be differentiated from the soil contamination reported 

 by Mullerand Sprugel (1977). They reported that the source of the ^^*Pu in the soil 1 

 mile east of the Laboratory was aerial emissions from stacks. These emissions were not 

 characterized physically or chemically (MuUer and Sprugel, 1977). 



Oak Ridge National Laboratory^ The ORNL site involves two different contaminating 

 situations. One of the sites was formerly a holdup pond of wastewater for radionuclide 

 retention. After the pond was drained in 1944, the bottom sediment was exposed, and a 

 young forest developed on the floodplain. The depth distribution of the plutonium 

 suggests that the plutonium was sorbed on particles that settled to the bottom. The 8M 

 nitric acid extraction revealed that 60 to 75% was soluble at room temperature and 1-hr 

 extraction. This relatively high extraction suggests a monomeric hydrolyzed form of 

 plutonium. 



The second site of contamination was the bottom sediment of a pond that served 

 initially as a waste-receiving pond for ORNL liquid waste. With an improved 

 waste-management system, the pond then served as a secondary settling pond for effluent 

 from a low-level wastewater treatment plant (Tamura, Sealand, and Duguid, 1977). The 

 higher activity level in the pond and its close proximity to ORNL suggest that the pond 

 served as the primary waste retention system before overflowing into the White Oak 

 Creek. The 8M nitric acid extraction revealed that 90% of the Pu in this sediment was 

 soluble. 



Citric acid extractability of the NTS, ML, and ORNL (tloodplain) samples has been 

 pubhshed (Tamura, 1976). The increasing order of extraction by the citrate was: NTS, 

 1%; ORNL, 25%; and ML, 50%. The time of contact of the citric acid with the sohds was 

 30 min at room temperature. Unpublished data by these investigators show that citric 

 acid treatment of the RF sample extracted approximately 1 0% of the plutonium. 



The percentage range in Pu extractability by the mineral acid and citric acid from the 

 different site samples reveals the differences in the plutonium at these sites. Although not 

 established quantitatively, these differences should also be reflected in the uptake 

 coefficients of vegetation grown at the sites. The extraction data presented further 

 suggest that plutonium derived from metallic sources, such as at NTS and RF, is less 

 soluble than that derived from an initially solubilized form, such as at ML and ORNL. 



