Geochemical partitioning of actinides using sequential chemical extractions: Comparison to stable elements

Abstract

We have developed a sequential extraction technique for determining the geochemical partitioning of Am, Pu, and U in soils and sediments. Stable element analyses were combined with radiometric measurements to determine the most probable geochemical host phases of these actinides in reference sediment IAEA-135.241Am results indicate an association with carbonate minerals and organic matter. The extraction profile of 238U was similar to that of refractory elements A1, Ti, and K. 239/24~ data suggest a fractionation of Pu into Fe-bearing phases of varying solubility. The reproducibility of the method was quite good (replicates agreed to within 10% at a 95% confidence level).

Concentration and speciation of plutonium, americium, uranium, thorium, potassium and 137Cs in a venice canal sediment sample

“…Although the geographical sites, the contaminants origin and the preliminariy treatment were quite different, the fractionation features found in this paper and in the Sellafield sediment [6] were not so different. The relatively more "insoluble" behaviour found in reference [6] for Am, Pu, U and Ba could be due to the collection date (1991) and the drying, homogenizing and storage treatments performed by IAEA, as declared also by the Authors themselves.…”

“…Due to the low concentration of plutonium, and consequently of 241Am, a 50 g wet sample had to be analyzed making the radioanalytical procedure more complicated if compared with other similar researches where it was possible to attack only 1-2 g of sample [6]. For the determination of the total concentration the wet sample was dried and heated in a muffle at 600 ~ for two hours; the dry matter was milled and stirred for one hour with 100 mL of conc.…”

“…The same conclusions were drown by Schultz at al. [6] for the an IAEA standard sediment coming from Sellafield (U. K.). The ratio 238pu/239+24~ was found to be 0.02 indicating that plutonium had only a fall out origin by nuclear weapon tests.…”

Speciation of naturally-accumulated uranium in an organic-rich soil of an alpine region (Switzerland)

“…Dried, homogenized powder from the various slices of core C3a was subjected to a sequential extraction method optimized for the quantification of actinides bound to an organic-rich soil (Schultz et al, 1998) to determine the soil fraction to which U is bound. Additionally total U was measured by complete digestion of the same samples as described above.…”

“…The release of U from a wet homogenized soil sample from core C3a (2 g from a depth of 17 cm in a 30 mL suspension) was investigated in the presence of oxygen as a Table 1 Sequential extraction procedure applied for each 2 g (dry weight) sample in 50 mL reactant (Schultz et al, 1998).…”