Speciation radionuclides

Lujaniene G, Lujanas V, Jankunaite D, et al. 1999. Speciation of radionuclides of the Chernobyl origin in aerosol and soil samples. J Environ Radioact 49 107-114. 

The retardation equation can also be applied to inorganic soluble substances (ions, radionuclides, metals). But here we have to consider, in addition to the sorption or ion exchange process, that the speciation of metal ions or ligands in a multi-... 

The fete of radionuclides in the marine environment is similar to that of the stable isotopes, being dependent on chemical speciation, including redox state, solubility, and tendency to form complex ions. For example, Pu and Am are particle reac-... 

Accuracy. Quantitative estimates of radionuclide solubility and speciation need reliable thermodynamic data, that is,... 

Bradbury Baeyens (2002a, b) provided sorption data bases for Opalinus Clay and MX-80 bentonite, respectively, based on numerous experiments with varying aqueous solution compositions. Since sorption can be influenced by the complexa-tion of radionuclides with various ligands, corrections had to be made to account for the differences in speciation between the experimental solutions and the Opalinus Clay and bentonite porewaters. For this purpose, the Nagra/PSI TDB 01 /01 was used to model the speciation of all safety-relevant radionuclides in the experimental solutions and in the Opalinus Clay and bentonite porewaters. 

Further applications of laser ablation inductively coupled plasma mass spectrometry for the trace and ultratrace and isotope analysis of long-hved radionuclides are discussed in references1 3,9actinide elements is presented by Geipel.91... 

Heavy metals, arsenic speciation, mercury speciation, organophosphates, organochlo-rine pesticides, VOCs, dichloroethane, trichloroethylene cotinine, nitrates and nitrites, creosote, PAHs (wood smoke), radionuclides, cyanide, dioxin-furan, disinfection byproducts, perchlorates, phthalate metabolites, thiodiglycol (mustard gas), sarin... 

Moulin, V., and Moulin, C. (2001). Radionuclide speciation in the environment a review. Radiochim. Acta 89,773-778. 

For these reasons, it is useful to evaluate the effects of forming or not forming aqueous sulfide complexing agents and sulfide precipitates on radionuclide solubilities and aqueous speciation. Therefore, calculations were performed for key radionuclides for two cases (1) reduction of sulfate to sulfide and bisulfide was allowed to occur as Eh was lowered and (2) sulfate reduction as a function of Eh was prohibited so that sulfate was the only sulfur complexing agent available at all Eh values. 

Of the elements considered in this study (see Table II), nickel, palladium, antimony, and lead are particularly sensitive to the presence of reduced sulfur species (S2, HS") in the groundwater. For each of these radionuclides, if sulfur speciates under thermodynamic equilibrium conditions, solid sulfide phases will control their solubility at low Eh values. The implication of this fact is illustrated in Figure 1 by a bold, dashed line that corresponds to the solubility of nickel in the reference groundwater and a patterned zone representing the total range... 

A complete summary of the results of the solubility computations for all radionuclides considered is found in Table n. The solubility values listed assume no sulfur speciation and are for a reference Eh of -0.3 V. This value is approximately midway between estimates of Eh from basalt-mineral equilibria and direct measurements of Grande Ronde groundwaters. 

A number of studies have been reported in the literature in which theoretical aqueous speciation of key radionuclides has been determined from available thermodynamic data (4.9.21-25). In general, where comparisons are possible, one finds reasonably close agreement in the calculated dominant dissolved species, the solids controlling solubility, and computed total solubilities for this study and those listed above. 

It has been the underlying theme of this paper that the theoretical approach to solubility and speciation of key radionuclides adopted here can be helpful in identifying the general types of species likely to be dominant in aqueous solutions. At present, these estimates are useful in identifying those radionuclides that require special attention in repository performance assessment studies. However, sophisticated experimental studies are necessary to provide important confirmatory data for nuclides of critical importance to the safe isolation of nuclear waste in a repository in basalt. 

The presence of relatively high levels of strong organic chelators like EDTA in the water samples prompted a detailed chemical speciation study aimed at determining whether the organic compounds identified in the survey study are chelated or complexed to radionuclides. Water samples from waste trenches 19S and 27 and inert atmosphere wells WIN and W2NA were fractionated by steric exclusion chromatography and subsequently analyzed for their... 

This second edition retains the structure of the first edition. It aims to provide a comprehensive review of the current science of speciation, covering relevant methodological, analytical and modelling aspects as well as giving an overview of recent work on speciation in various spheres. It is divided into two parts, the first dealing with the more methodological aspects and the second with specific compartments of the environment, with the speciation of radionuclides, and presents a review of current trends and developments. 

Part II considers speciation in specific compartments of the environment viz. the atmosphere, biological systems, soils, sediments and natural waters, and with particular aspects of the speciation of environmentally important radionuclides. Two new chapters have been added to make the coverage even more comprehensive. These new chapters are Chapter 10, Chemical Speciation in Soib and Related Materials by Selective Chemical Extraction by the editors, and Chapter 12, Speciation in Seawater by R.H. Byrne of the University of South Florida. 

Classical speciation of radionuclides is described in Chapter 13. Methodology for single and sequential extraction of soil to assess radionuclide availability to plants is similar to that used for heavy metals, and has recently been reviewed (Kennedy et al., 1997). Therefore, only recent applications of sequential extraction to speci-ate both natural and anthropogenic nuclides are discussed below. 

It is clear from previous comments that radionuclide speciation studies must consider not only oxidation states and specific inorganic forms but also complex species arising through association with natural organic matter and the possibility of different physical states. The relative importance of these various physicochemical forms will, in practice, be dictated by a combination of the basic elemental characteristics of the radionuclide and the type of environment into which it is placed. Thus in seawater, colloidal organic complex species are likely to be far less dominant than for the same radionuclide in a very low ionic strength freshwater. In the case of soil and sediment interstitial waters or groundwaters,... 

Especially interesting in a discussion of radionuclide speciation is the behaviour of the transuranium elements neptunium, plutonium, americium and curium. These form part of the actinide series of elements which resemble the lanthanides in that electrons are progressively added to the 5f instead of the 4f orbital electron shell. The effective shielding of these 5f electrons is less than for the 4f electrons of the lanthanides and the differences in energy between adjacent shells is also smaller, with the result that the actinide elements tend to display more complex chemical properties than the lanthanides, especially in relation to their oxidation-reduction behaviour (Bagnall, 1972). The effect is especially noticeable in the case of uranium, neptunium and plutonium, the last of which has the unique feature that four oxidation states Pum, Pu, Puv and Pu are... 

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