UPTAKE OF TRANSURANIC NUCLIDES FROM SOIL BY PLANTS 337 



Plant uptake of transuranic elements via the root path has been the subject of recent 

 reviews (Francis, 1973; Price, 1972a; Brown. 1976; Bernhardt and Eadie, 1976; Mueller 

 and Mosley, 1976). There has been partial synthesis of the data, with most of the 

 emphasis on outlining the problems needing further study. 



Recently, Adriano et al. (1977), Romney, Mork, and Larson (1970), and Wallace 

 (1969) found that the chelating agent DTPA (diethylenetriamine pentaacetic acid) 

 enhanced plant uptake of both ^ ^ ^ Am and ^ ^ ^ Pu up to at least one order of magnitude 

 under some conditions. These observations, confirmed by their subsequent studies, are 

 important for two reasons: (1) chelating agents are used in the nuclear industry and are 

 often present in wastes, and (2) chelating agents are also used in plant nutrition to supply 

 micronutrients to plants and therefore are likely to be present in agricultural soils. 

 Agricultural soils are usually treated with various types of amendments to optimize crop 

 production. Such amendments, like lime, organic matter, and fertilizers, change the 

 chemistry of the soil with a concomitant effect on the availability of the elements in 

 question and their subsequent translocation to the plant shoots. 



Tlie main objective of this chapter is to evaluate how various soil factors, both 

 indigenous and introduced, affect uptake of the transuranic elements by various plant 

 species grown in potted soils obtained from two distinct regions of the United States: the 

 desert soils of the western United States and soils of the humid southeastern United 

 States. 



Materials and Methods 



Pot-Culture Experiments with Soils Representing the Humid 

 Environments of the Southeastern United States 



The soils used for the Bahia grass and rice experiments were collected from the Savannah 

 River Plant (SRP), near Aiken, S. C. These were uncontaminated soils, higlily weathered 

 Ultisols, which were collected from the topsoil in a location that normally receives 

 approximately 130 cm of rainfall annually. These soils are either common in the coastal 

 plain area or similar to the soils found at the burial areas for nuclear wastes at Barnwell, 

 S. C, and at the SRP. The clay is usually reddish owing to ferric oxide and is dominated 

 by kaolin. 



Bahia Grass Experiment. Collection, preparation, liming, spiking of soils, and potting 

 of soils (Troup sandy loam and Dothan sandy clay loam) are described in detail in a 

 previous paper (Adriano et al., 1977). Bermuda grass hay was ground to pass a 20-mesh 

 screen and mixed with both the limed and unlimed soils to give 0.0, 1.25, and 5.0% 

 organic matter (OM) by weight. Reagent-grade fertilizers (NH4NO3, KH2PO4, and 

 KNO3), lime, and OM were mixed well at the same time with each 2 kg of soil in plastic 

 bags. 



A 500-g aliquot of the premixed soils was removed from each pot (top diameter, 

 1 5 cm; bottom diameter. 1 2.5 cm; height. 13.5 cm) and used for spiking. One microcurie 

 of ^"^^ Am. dissolved in 1 ml of 0.1 A^ HNO3. was placed in 125 ml of distilled water; then 

 10-ml aliquots of this solution were pipeted and added to a thin layer of soil 

 (approximately 40 g) placed on top of the remaining soil. This was repeated until the 

 total 500 g of soil was spiked. 



Each treatment of the complete factorial (two soil types x two lime rates x three OM 

 rates) was replicated seven times, but only tlve replicates were spiked. The two unspiked 



