Aqueous and solid phase interactions of radionuclides with organic complexing agents (original) (raw)
Related papers
Environmental Pollution, 2010
The adsorption behavior of 241 Am, 60 Co, 137 Cs and 85 Sr in the presence and absence of chelating ligands (ethylenediaminetetraacetic acid, ethylenediaminediacetic acid, hydroxyethyliminodiacetic acid, iminodiaceiticacid and methyliminodiacetic acid) was investigated. Sorption affinity in the absence of chelating ligands followed: Am(III) > Co(II) > Cs(I) > Sr(II). The presence of chelating ligands generally had little effect on sorption of 85 Sr and 137 Cs with K d values 110 and 690 mL g À1 , respectively. But at 0.02 M of ethylenediaminetetraacetic or hydroxyethyliminodiacetic, the K d decreased to 5 or 63 mL g À1 , respectively, where thermochemical modeling indicated almost all 85 Sr is complexed with these ligands. The K d values for 241 Am and 60 Co generally decreased with increasing chelating agent concentrations. In notable cases, the K d values for Am increased at specific concentrations of 10 À3 M for IDA, MIDA and 10 À4 M for EDDA. This is proposed to be due to formation of a ternary surface complex.
Speciation of Radionuclides in the Environment
Applications, Theory and Instrumentation, 2006
To obtain information on physicochemical forms of radionuclides in the environment, speciation techniques should be applied in situ, at-site or in laboratories shortly after sample collection. Among speciation techniques for radionuclides in waters, combined in situ ultrafiltration and exchange chromatography are most promising as radionuclides species are fractionated with respect to nominal molecular mass and change properties simultaneously. However, the fractionation and characterization of chemically well-defined low molecular mass (LMM) species in waters is still a challenge. Surface analytical techniques (e.g. electron microscopy) are useful for characterizing colloids and particles with respect to structure and radionuclide distribution. Recent development within synchrotron-based X-ray microbeam techniques allows detailed information of crystallographic structure (micro-X-ray diffraction (µ-XRD)), oxidation states (micro-X-ray absorption near-edge spectroscopy (µ-XANES)) and volume distribution (µ-XANES tomography) of particle-associated radionuclides on the micrometer scale. Information on radionuclides reversibly or irreversibly associated with solid surfaces (binding mechanisms) is attained by different extraction techniques, while dynamic tracer experiments can provide information on the kinetics involved.
Radionuclide speciation and its relevance in environmental impact assessments
Journal of Environmental Radioactivity, 2004
To assess the long-term environmental impact of radioactive contamination of ecosystems, information on source terms including radionuclide speciation, mobility and biological uptake is needed. A major fraction of refractory radionuclides released from nuclear sources such as nuclear weapons tests and reactor accidents is present as radioactive particles, whilst radionuclides are also present as colloids or low molecular mass species in effluents from nuclear installations. Low molecular mass species are more mobile (lower apparent Kd) and bioavailable (higher apparent BCF) than colloids and particles. Soils and sediments act as sinks for particles and colloids. Due to particle weathering, associated radionuclides can be remobilised over time. Thus, information on particle characteristics such as composition, particle size, crystalline structures and oxidation states influencing weathering rates and subsequent mobilisation is essential. The present article summarises current knowledge on radioactive particles released from different sources, and the relevance of radionuclide speciation for mobility and biological uptake.
Biogeochemical behaviour of anionic radionuclides in soil: Evidence for biotic interactions
Radioprotection, 2005
99 Tc and 79 Se, two long-lived radionuclides, are supposed to be highly mobile in soils, because of their anionic forms. Their behaviours in the soil are often considered only from a physico-chemical point of view, although the microorganisms can affect either directly or indirectly their speciation. This study demonstrates the role of the microbial compartment in the retention of Se and Tc in soil by comparing experiments with soils constrained to different microbiological status (sterile / raw / amended). Kd coefficients for Se and Tc were determined in batch experiments, whereas transport of Se and Tc was investigated through column leaching experiments. Kd for Se was enhanced for the raw soil without amendment compared to the value obtained for the sterilised soil. The retention of Se was higher again in the amended soil. Besides, a biofilm, which can directly retain Se, was obtained at the entrance of the amended soil column. This effect was less obvious for Tc in batch experiments, but was revealed by leaching experiments where a high quantity of Tc was retained in the amended soil columns. These results give strong evidence that microorganisms are responsible for a greater retention of Se and Tc in soil.
Understanding Sorption Behavior and Properties of Radionuclides in the Environment
Principles and Applications in Nuclear Engineering - Radiation Effects, Thermal Hydraulics, Radionuclide Migration in the Environment, 2018
Prediction of fate and behavior of radionuclides in the environment is largely governed by sorption processes. Radionuclides physico-chemical species interacting with prevailing abiotic properties of the environment vary widely among varying constituting environmental components. Herein, this work discussed the most significant aspects of sorption processes and properties at the solid-water interface. Main sorption mechanisms were investigated using kinetic, thermodynamic analyses, and various mathematical models in current use for description of sorption-desorption processes in the environment. Knowledge of environmental transport, environmental pathways, and exposure pathways to radionuclides is also an important aspect of any strategy to protect the public and the natural ecosystems. In the final analysis, the choice of a functional sorption equation model will be dictated by the risk-based under consideration, the level of information available, and the intrinsic accuracy of the predictive model.
Journal of Environmental Radioactivity, 2017
Among the key environmental factors influencing the fate and transport of radionuclides in the environment is natural organic matter (NOM). While this has been known for decades, there still remains great uncertainty in predicting NOM-radionuclide interactions because of lack of understanding of radionuclide interactions with the specific organic moieties within NOM. Furthermore, radionuclide-NOM studies conducted using modelled organic compounds or elevated radionuclide concentrations provide compromised information related to true environmental conditions. Thus, sensitive techniques are required not only for the detection of radionuclides, and their different species, at ambient and/or far-field concentrations, but also for potential trace organic compounds that are chemically binding these radionuclides. GC-MS and AMS techniques developed in our lab are reviewed here that aim to assess how two radionuclides, iodine and plutonium, form strong bonds with NOM by entirely different mechanisms; iodine tends to bind to aromatic functionalities, whereas plutonium binds to N-containing hydroxamate siderophores at ambient concentrations. While low-level measurements are a prerequisite for assessing iodine and plutonium migration at nuclear waste sites and as environmental tracers, it is necessary to determine their in-situ speciation, which ultimately controls their mobility and transport in natural environments. More importantly, advanced molecular-level instrumentation (e.g., nuclear magnetic resonance (NMR) and Fourier-transform ion cyclotron resonance coupled with electrospray ionization (ESI-FTICRMS) were applied to resolve either directly or indirectly the molecular environments in which the radionuclides are associated with the NOM.
Migration of Radionuclides in Geologic Media: Fundamental Research Needs
MRS Proceedings, 1990
ABSTRACTAn assessment of the fundamental research needs in understanding and predicting the migration of radionuclides in the subsurface is provided. Emphasis is on the following three technical areas: (1) aqueous speciation of radionuclides, (2) the interaction of radionuclides with substrates, and (3) intermediate-scale interaction studies. This research relates to important issues associated with environmental restoration and remediation of DOE sites contaminated with mixed radionuclide-organic wastes.
2016
The objective of this project was to study the influence of increased salinities on interaction processes in the system radionuclideorganicsclayaquifer. For this purpose, complexation, redox, sorption, and diffusion studies were performed under variation of the ionic strength (up to 4 mol kg −1) and the background electrolyte (NaCl, CaCl 2 , MgCl 2). The complexation of U(VI) by propionate was studied in dependence on ionic strength (up to 4 mol kg −1 NaClO 4) by combining time-resolved laser-induced fluorescence spectroscopy (TRLFS), attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy, and density functional theory (DFT) calculations. U(VI)/propionate complexes with a 1:1, 1:2, and 1:3 stoichiometry were identified. The stability constants were found to vary with ionic strength, whereby the ionic strength influence depended on the charge of the respective complexes. The conditional stability constants, determined for UO 2 (Prop) + , UO 2 (Prop) 2 0 and
Speciation Analysis of Radionuclides in the Environment - NSK-B SPECIATION project report 2009
2009
The second stage of the NKS-B project SPECIATION was complemented in 2008-2009, which mainly focus on three aspects: (1) Further improvement and development of methods for speciation analysis of radionuclides; (2) Investigation of speciation of some radionuclides in the environment (water, sediments, particles); and (3) Intercomparison excise for speciation analysis of radionuclides in soil and sediment. This report summarizes the work completed in the project partners' laboratories, Method developments include: Development of an rapid and in-suit separation method for the speciation analysis of 129I in seawater samples; Development of a simple method for the speciation analysis of 129I in fresh water and seawater samples; Development of an on-line HPLC-ICP-MS method for the direct speciation analysis of 127I in water and leachate samples; Speciation of radionuclides in water includes: Speciation of 129I and 127I in time-series precipitation samples collected in Denmark 2001-2006 and its application for the investigation of geochemistry and atmospheric chemistry of iodine, Speciation of radionuclides in Ob and Yenisey Rivers, and Speci-ation of 129I and 127I in Lake Heimdalen water. Speciation of radionuclides in soils and sediments includes: Sequential extraction of radionuclides in sediments and of trace elements in soil samples. Sequential extraction of radionuclides in aerosols and particles has also been performed. Furthermore , sorption experiments have been performed to investigate the association of Pu, Am and Cs with different geological materials. The intercomparison exercises included sequential extraction of Pu, 137Cs, U, Th, and 129I in one soil and one sediment standard reference materials (NIST-4354, IAEA-375) and Pu in sediment collected from the Lake Heimdalen, Norway.