A novel approach to the sequential extraction of plutonium from oxic and anoxic sediment using sodium citrate to inhibit post-extraction resorption

• Published in: Journal of environmental radioactivity Vol. 93; no. 2; pp. 63 - 73
• Main Authors: Lucey, Julie A., Vintró, Luis León, Boust, Dominique, Mitchell, Peter I., Gouzy, Aurélien, Bowden, Louise
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.01.2007; Elsevier
• Subjects: Absorption; Analysis methods; Anoxic sediments; Applied sciences; Citrates - chemistry; Continental interfaces, environment; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Geologic Sediments - chemistry; Oxygen - chemistry; Particle Size; Plutonium; Plutonium - chemistry; Plutonium - isolation & purification; Pollution; Pollution, environment geology; Radiation Monitoring; Resorption; Sciences of the Universe; Sequential extraction analysis; Sodium citrate; Soil and sediments pollution; Soil Pollutants, Radioactive - chemistry; Soil Pollutants, Radioactive - isolation & purification; Time Factors; Resorption; Sequential extraction analysis; Plutonium; Anoxic sediments; Sodium citrate; Radioactive pollution; Sequential extraction; Radioisotope; Sediments; Sample preparation; Adsorption; Organic salt; Chelating agent
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2006.11.004

Sequential extraction has been used extensively to study the solid partitioning of radionuclides in soils and sediments. A difficulty with sequential extraction is that radionuclides released by a particular extractant can be resorbed and artificially redistributed amongst the remaining solid phases. Here, we describe experiments (on selected model phase and natural materials), which were designed to determine whether the inclusion of a chelating agent (sodium citrate) in an established sequential extraction protocol (a) inhibits post-extraction resorption of plutonium, (b) increases non-targeted dissolution of sediment phases, and (c) gives rise to unwanted ligand competition for plutonium. The results clearly demonstrate the capacity of citrate to inhibit the resorption of plutonium from the various extractants, and confirm that there is no discernible increase in non-targeted phase dissolution, but indicate significant ligand competition with the carbonate phase. The merits of using citrate are discussed and an optimised sequential extraction protocol that includes citrate is proposed. Finally, the protocol is applied to oxic and anoxic sediments sampled in the NE Irish Sea and the Roads of Cherbourg, and it is shown that the bulk of the plutonium on these sediments is associated with the more labile geochemical fractions.