Determination of 135Cs and 137Cs in environmental samples: A review

Incorporating solvent effects in DFT: insights from cation exchange in faujasites

Zeolites are versatile materials renowned for their extra-framework cation exchange capabilities, with applications spanning diverse fields, including nuclear waste treatment. While detailed experimental characterization offers valuable insight, density functional theory (DFT) proves particularly adept at investigating ion exchange in zeolites, owing to its atomic and electronic resolution. However, the prevalent occurrence of zeolitic ion exchange in aqueous environments poses a challenge to conventional DFT modeling, traditionally conducted in a vacuum. This study seeks to enhance zeolite modeling by systematically evaluating predictive differences across varying degrees of aqueous solvent inclusion. Specifically focusing on monovalent cation exchange in Na-X zeolites, we explore diverse modeling approaches. These range from simple dehydrated systems (representing bare reference states in vacuum) to more sophisticated models that incorporate aqueous solvent effects through explicit water molecules and/or a dielectric medium. Through comparative analysis of DFT and semi-empirical DFT approaches, along with their validation against experimental results, our findings underscore the necessity to concurrently consider explicit and implicit solvent effects for accurate prediction of zeolitic ionic exchange.

Design and Synthesis of Covalently Tethered "IsoG-Star" as Recyclable Host for Selective Cesium Separation

The isoguanosine self-assembled pentamer (isoG-star) has exhibited remarkable selectivity for Cs+ binding over competing alkali and alkali earth metal cation, rendering it a promising extractor for radioactive waste 137Cs separation. However, to make isoG-star a pracrtical material for Cs+ isolation, the development of recyclable isoG-star material is required. In this study, a systematic screening of functional isoG derivatives was performed. By employing well-defined complex formation and post-assembly modification, a covalently tethered isoG5-star was prepared through olefin metathesis, utilizing a designed isoG monomer. The application of this newly developed covalently linked isoG-star enabled selective Cs+ extraction, followed by controled solvent-induced H-bond dessociation. This resulted in the creation of a recyclable Cs+ extractor, demonstrating excellent cation selectivity and good reusability (over seven cycles) the first time. Consequently, this new supramolecular macrocycle offers a practical new platform for the treatment of radiocesium (134Cs and 137Cs) in an environmentally friendly and highly effective manner.

Disproportionately High Contributions of 60 Year Old Weapons-137Cs Explain the Persistence of Radioactive Contamination in Bavarian Wild Boars

Radionuclides released from nuclear accidents or explosions pose long-term threats to ecosystem health. A prominent example is wild boar contamination in central Europe, which is notorious for its persistently high 137Cs levels. However, without reliable source identification, the origin of this decades old problem has been uncertain. Here, we target radiocesium contamination in wild boars from Bavaria. Our samples (2019-2021) range from 370 to 15,000 Bq·kg-1 137Cs, thus exceeding the regulatory limits (600 Bq·kg-1) by a factor of up to 25. Using an emerging nuclear forensic fingerprint, 135Cs/137Cs, we distinguished various radiocesium source legacies in their source composition. All samples exhibit signatures of mixing of Chornobyl and nuclear weapons fallout, with 135Cs/137Cs ratios ranging from 0.67 to 1.97. Although Chornobyl has been widely believed to be the prime source of 137Cs in wild boars, we find that "old" 137Cs from weapons fallout significantly contributes to the total level (10-68%) in those specimens that exceeded the regulatory limit. In some cases, weapons-137Cs alone can lead to exceedances of the regulatory limit, especially in samples with a relatively low total 137Cs level. Our findings demonstrate that the superposition of older and newer legacies of 137Cs can vastly surpass the impact of any singular yet dominant source and thus highlight the critical role of historical releases of 137Cs in current environmental pollution challenges.

Identification of the origin of radiocesium released into the environment in areas remote from nuclear accident and military test sites using the 135Cs/137Cs isotopic signature

The isotopic signature of radionuclides provides a powerful tool for discriminating radioactive contamination sources and estimating their respective contributions in the environment. In this context, the ¹³⁵Cs/¹³⁷Cs ratio has been tested as a very promising isotopic ratio that had not been explored yet in many countries around the world including France. To quantify the levels of radioactivity found in the environment, a new method combining a thorough radiochemical treatment of the sample and an efficient measurement by ICP-MS/MS has been recently developed. This method was successfully applied, for the first time, to soil and sediment samples collected in France in two mountainous regions preferentially impacted either by global fallout from nuclear weapons testing (i.e., the Pyrenees) or by the Chernobyl accident (i.e., the Southern Alps). The ¹³⁵Cs/¹³⁷Cs ratios measured on twenty-one samples ranged from 0.66 ± 0.04 and 4.29 ± 0.21 (decay-corrected to January 1st, 2022) corresponding to the characteristic signatures of the fallout from Chernobyl and global fallout associated with the nuclear weapons testing, respectively. Moreover, large variations of both the ¹³⁷Cs mass activity and the studied isotopic ratio recorded by most samples from the southern Alps suggest varying proportions of these two ¹³⁷Cs sources. For these samples, the contribution of each source was estimated using this new tracer (¹³⁵Cs/¹³⁷Cs) and compared with the mixing contribution given by activity ratio: ^239+240Pu/¹³⁷Cs. This work has successfully demonstrated the applicability of the ¹³⁵Cs/¹³⁷Cs isotopic signature to nuclear forensic studies and could be extended to better evaluate the environmental impact of nuclear facilities (i.e., NPP, waste reprocessing).

Innovative ICP-MS/MS Method To Determine the 135Cs/137Cs Ratio in Low Activity Environmental Samples

The ¹³⁵Cs/¹³⁷Cs isotopic ratio is a powerful tool for tracing the origin of radioactive contamination. Since the Fukushima accident, this ratio has been measured by mass spectrometry in several highly contaminated environmental matrices mainly collected near nuclear accident exclusion zones and former nuclear test areas. However, few data were reported at ¹³⁷Cs environmental levels (<1 kBq kg^-1). This is explained by the occurrence of analytical challenges related to the very low radiocesium content at the environmental level with the large presence of mass interferences, making ¹³⁵Cs and ¹³⁷Cs measurements difficult. To overcome these difficulties, a highly selective procedure for Cs extraction/separation combined with an efficient mass spectrometry measurement must be applied on a quantity of ca. 100 g of soil. In the current research, an innovative inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS) method has been developed for the ¹³⁵Cs/¹³⁷Cs ratio measurement in low activity environmental samples. The use of ICP-MS/MS led to a powerful suppression of ¹³⁵Cs and ¹³⁷Cs interferences by introducing N₂O, He, and, for the first time, NH₃, into the collision-reaction cell. By adjusting the flow rates of these gases, the best compromise between a maximum signal in Cs and an effective interference elimination was achieved allowing a high Cs sensitivity of more than 1.10⁵ cps/(ng g^-1) and low background levels at m/z 135 and 137 lower than 0.6 cps. The accuracy of the developed method was successfully verified by analyzing two certified reference materials (IAEA-330 and IAEA-375) commonly used in the literature as validation samples and three sediment samples collected in the Niida River catchment (Japan) impacted by the Fukushima fallout.

Recent Development on Determination of Low-Level 90Sr in Environmental and Biological Samples: A Review

In the context of the rapid development of the world's nuclear power industry, it is vital to establish reliable and efficient radioanalytical methods to support sound environment and food radioactivity monitoring programs and a cost-effective waste management strategy. As one of the most import fission products generated during human nuclear activities, ⁹⁰Sr has been widely determined based on different analytical techniques for routine radioactivity monitoring, emergency preparedness and radioactive waste management. Herein, we summarize and critically review analytical methods developed over the last few decades for the determination of ⁹⁰Sr in environmental and biological samples. Approaches applied in different steps of the analysis including sample preparation, chemical separation and detection are systematically discussed. The recent development of modern materials for ⁹⁰Sr concentration and advanced instruments for rapid ⁹⁰Sr measurement are also addressed.

Identification, isolation, and characterization of a novel type of Fukushima-derived microparticle

In the course of the Fukushima nuclear accident, radionuclides were released in various forms, including so-called radiocesium-bearing microparticles (CsMP). So far, four types of CsMP were described: Type A is smaller in size (< 10 μm), Types B, C, and D are larger (> 100 μm). In this work, we present a novel type of CsMP (proclaimed Type E). Three particles of Type E were extracted from a contaminated blade of grass that was sampled 1.5 km from the Fukushima Daiichi nuclear power plant in late 2011. They were located using autoradiography, isolated using an optical microscope and micromanipulator, and characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy, and low-level gamma-ray spectrometry. Type E CsMPs are 10–20 μm in size and exhibit an unusually low and barely detectable 137Cs activity of only ≤ 10 mBq per particle. Their brittle and fragile character may indicate a high surface tension.

Determination, Separation and Application of 137Cs: A Review

In the context of the rapid development of the world's nuclear power industry, it is necessary to establish background data on radionuclides of different samples from different regions, and the premise of obtaining such basic data is to have a series of good sample processing and detection methods. The radiochemical analysis methods of low-level radionuclides ¹³⁷Cs (Cesium) in environmental and biological samples are introduced and reviewed in detail. The latest research progress is reviewed from the five aspects of sample pretreatment, determination, separation, calculation, application of radioactive cesium and the future is proposed.

226Ra and 137Cs determination by inductively coupled plasma mass spectrometry: state of the art and perspectives including sample pretreatment and separation steps

Achieving precise and accurate quantification of radium (²²⁶Ra) and cesium (¹³⁷Cs) by inductively coupled plasma mass spectrometry (ICP-MS) is of particular interest in the field of radiological monitoring and more widely in environmental and biological sciences. However, the accuracy and sensitivity of the quantification depend on the analytical strategy implemented. Eliminating interferences during the sample handling step and/or during the analysis step is critical since presence of matrix elements can lead to spectral and non-spectral interferences in ICP-MS. Consequently, before the ICP-MS analysis, multiple sample preparation approaches have been applied to purify and/or pre-concentrate environmental and biological samples containing radium and cesium through years, such as (co)-precipitation, solid phase extraction (SPE) or dispersive SPE (dSPE). Separation steps using liquid chromatography and capillary electrophoresis can also be useful in complement with the abovementioned sample preparation techniques. The most attractive sample handling technique remains SPE but efficiency of the extraction procedures is currently limited by sorbent specificity. Indeed, with the recent advances in ICP-MS instrumentation, it becomes indispensable to eliminate residual interferences and improve sensitivity. It is in this direction that it will be possible to meet analytical challenges, e.g. analyzing radium and cesium at concentrations below the pg L^-1 range in complex matrices of small volumes, as they are found for instance in pore waters or in biological samples. Development of new innovative sorbents based for example on hybrid and nanostructured materials has been reported with the aim of enhancing sorbent specificity and/or capacity. In the present review, the performances of the different analytical approaches are discussed, followed by an overview of applications.

A review on the use of lichens as a biomonitoring tool for environmental radioactivity

Lichens have been widely used as a biomonitoring tool to record the distribution and concentration of airborne radioactivity and pollutants such as metals. There are limitations, however: although pollutants can be preserved in lichen tissues for long periods of time, not all radioactive and inert elements behave similarly. The chemical species of elements at the source, once captured, and the mode of storage within lichens play a role in this biomonitoring tool. Lichens are a symbiotic association of an algal or cyanobacterial partner (photobiont) with a fungal host (mycobiont). Lichens grow independently of the host substrates, including rocks, soils, trees and human-made structures. Lacking a root system, lichen nutrient or contaminant uptake is mostly through direct atmospheric inputs, mainly as wet and dry deposition. As lichens grow in a large variety of environments and are resilient in harsh climates, they are adapted to capture and retain nutrients from airborne sources. The context of this review partially relates to future deployment of small modular reactors (SMRs) and mining in remote areas of Canada. SMRs have been identified as a future source of energy (electricity and heat) for remote off-grid mines, potentially replacing diesel fuel generation facilities. For licensing purposes, SMR deployment and mine development requires capabilities to monitor background contaminants (natural radioactivity and metals) before, during and after deployment, including for decommissioning and removal. Key aspects reviewed herein include: (1) how lichens have been used in the past to monitor radioactivity; (2) radiocontaminants capture and storage in lichens; (3) longevity of radiocontaminant storage in lichen tissues; and (4) limitations of lichens use for monitoring radiocontaminants and selected metals.

Sorption methods in marine radiochemistry

The review presents the general methodology of using sorption methods to solve problems of marine radiochemistry, including sampling, preconcentration and radiochemical preparation and methods for measuring the activity of radionuclides. The possible methodological errors at various stages of sampling and sample concentration are discussed. The most widely used artificial (90Sr, 134Cs, 137Cs, 239Pu, 240Pu), natural (210Pb, 210Po; radium quartet: 223Ra, 224Ra, 226Ra, 228Ra; thorium isotopes, mainly 234Th) and cosmogenic (7Be, 32P, 33P) radiotracers are considered. The sorption of uranium from seawater is not addressed, since its concentration in seawater is usually calculated from the known dependence of uranium concentration on seawater salinity.

The bibliography includes 200 references.

Determination of low-level 135Cs and 135Cs/137Cs atomic ratios in large volume of seawater by chemical separation coupled with triple-quadrupole inductively coupled plasma mass spectrometry measurement for its oceanographic applications

Radioisotopes of cesium are powerful tracer for oceanographic studies. In this work, a novel method was developed for determination of ultra-low level ¹³⁵Cs and ¹³⁷Cs in seawater using triple-quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS). Cesium was pre-concentrated from up to 45 L seawater samples using ammonium molybdophosphate (AMP) adsorption, following a selective leaching of cesium using Sr(OH)₂. The cesium was further purified from interfering elements using AMP-PAN and cation-exchange chromatography. Sr(OH)₂ leaching was found to be an effective approach for selective exchange of cesium from the AMP sorbent without dissolution, which avoids the problem of separation of huge amount of NH₄⁺ and MoO₄^2- in the following steps. The decontamination factors for barium and rubidium with the developed method were more than 4 × 10⁷ and 800, respectively. The separated ¹³⁵Cs and ¹³⁷Cs were measured using ICP-MS/MS by employing N₂O as reaction gas to further elimination of isobaric (i.e. ¹³⁵Ba and ¹³⁷Ba) and polyatomic ions interferences. A detection limit of 1.5 × 10^-16 g L^-1 for ¹³⁵Cs in seawater was achieved. The concentrations of ¹³⁵Cs in seawater from Baltic Sea, Danish straits and Roskilde Fjord were determined using the developed method to identify the sources of ¹³⁵Cs, the water masses exchange in this region was investigated using ¹³⁵Cs and ¹³⁷Cs.

Determination of Characteristic vs Anomalous 135Cs/137Cs Isotopic Ratios in Radioactively Contaminated Environmental Samples

A contamination with the ubiquitous radioactive fission product ¹³⁷Cs cannot be assigned per se to its source. We used environmental samples with varying contamination levels from various parts of the world to establish their characteristic ¹³⁵Cs/¹³⁷Cs isotope ratios and thereby allow their distinction. The samples included biological materials from Chernobyl and Fukushima, historic ashed human lung tissue from the 1960s from Austria, and trinitite from the Trinity Test Site, USA. After chemical separation and gas reaction shifts inside a triple quadrupole ICP mass spectrometer, characteristic ¹³⁵Cs/¹³⁷Cs isotope signatures (all as per March 11, 2011) were obtained for Fukushima- (∼0.35) and Chernobyl-derived (∼0.50) contaminations, in agreement with the literature for these contamination sources. Both signatures clearly distinguish from the characteristic high ratio (1.9 ± 0.2) for nuclear-weapon-produced radiocesium found in human lung tissue. Trinitite samples exhibited an unexpected, anomalous pattern by displaying a low (<0.4) and nonuniform ¹³⁵Cs/¹³⁷Cs ratio. This exemplifies a ¹³⁷Cs-rich fractionation of the plume in a nuclear explosion, where ¹³⁷Cs is a predominant species in the fireball. The onset of ¹³⁵Cs was delayed because of the longer half-life of its parent nuclide ¹³⁵Xe, causing a spatial separation of gaseous ¹³⁵Xe from condensed ¹³⁷Cs, which is the reason for the atypical ¹³⁵Cs/¹³⁷Cs fractionation in the fallout at the test site.

Determination of 135Cs concentration and 135Cs/137Cs ratio in waste samples from nuclear decommissioning by chemical separation and ICP-MS/MS

Determination of ¹³⁵Cs concentration and ¹³⁵Cs/¹³⁷Cs atomic ratio is of great importance in characterization of radioactive waste from decommissioning of nuclear facilities. In this work, an effective analytical method was developed for simultaneously determination of ¹³⁵Cs and ¹³⁷Cs in different types of waste samples (steel, zirconium alloy, reactor coolant, ion exchange filter paper and spent ion exchange resin) by coupling AMP-PAN, AG MP-1M and AG 50 W-X8 chromatographic separation with ICP-MS/MS measurement. Decontamination factors of 7.0 × 10⁶ for Co, 6.0 × 10⁶ for Ba, 4.2 × 10⁵ for Mo, 3.2 × 10⁵ for Sn and 2.1 × 10⁵ for Sb were achieved using the chemical separation procedure. The overall chemical yields of cesium were higher than 85%. A detection limit of 3.1 × 10^-14 g/g for ¹³⁵Cs was achieved for 0.2 g stainless steel sample or spent resin. The developed method was validated by analysis of standard reference materials (IAEA-375) and successfully applied for analysis of zirconium alloy, steel, ion exchange filter paper and spent ion exchange resin from nuclear power reactors. The obtained ¹³⁵Cs can be used to evaluate the long-term environmental impact and provide useful information for waste disposal. The measured ¹³⁵Cs/¹³⁷Cs ratio in reactor coolant, as a characteristic information, might be useful for source identification and localization of leaked fuel element. The neutron flux of the leaked fuel element can be estimated based on the measured ¹³⁵Cs/¹³⁷Cs atomic ratios in the reactor coolant water. The developed method is simple and rapid (8 samples/day) for the determination of ¹³⁵Cs concentrations and ¹³⁵Cs/¹³⁷Cs ratios in various waste samples from nuclear decommissioning.

Dose and Dose-Rate Effects in a Mouse Model of Internal Exposure to 137Cs. Part 1: Global Transcriptomic Responses in Blood

Internal contamination by radionuclides may constitute a major source of exposure and biological damage after radiation accidents and potentially in a dirty bomb or improvised nuclear device scenario. We injected male C57BL/6 mice with radiolabeled cesium chloride solution (137CsCl) to evaluate the biological effects of varying cumulative doses and dose rates in a two-week study. Injection activities of 137CsCl were 5.71, 6.78, 7.67 and 9.29 MBq, calculated to achieve a target dose of 4 Gy at days 14, 7, 5 and 3, respectively. We collected whole blood samples at days 2, 3, 5, 7 and 14 so that we can publish the issue in Decemberfrom all injection groups and measured gene expression using Agilent Mouse Whole Genome microarrays. We identified both dose-rate-independent and dose-rate-dependent gene expression responses in the time series. Gene Ontology analysis indicated a rapid and persistent immune response to the chronic low-dose-rate irradiation, consistent with depletion of radiosensitive B cells. Pathways impacting platelet aggregation and TP53 signaling appeared activated, but not consistently at all times in the study. Clustering of genes by pattern and identification of dose-rate-independent and -dependent genes provided insight into possible drivers of the dynamic transcriptome response in vivo, and also indicated that TP53 signaling may be upstream of very different transcript response patterns. This characterization of the biological response of blood cells to internal radiation at varying doses and dose rates is an important step in understanding the effects of internal contamination after a nuclear event.

Determination of Ultralow Level 135Cs and 135Cs/137Cs Ratio in Environmental Samples by Chemical Separation and Triple Quadrupole ICP-MS

An analytical method was developed for the determination of ultralow level ¹³⁵Cs in environmental samples by chromatographic separation of cesium with AMP-PAN and AG50W-X8 columns and sensitive measurement of cesium isotopes with triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS). Cesium was simply released by acid leaching using aqua regia from environmental solid samples and preconcentrated on AMP-PAN column. The cesium adsorbed on the column was effectively eluted with NH₄Cl solution without dissolving the AMP. The excessive amount of NH₄Cl in the eluate was removed by sublimation in the presence of small amount of LiCl. The remaining barium and other interfering elements such as Mo, Sn, Sb, and Li were efficiently removed using cation exchange chromatography (AG50W-X8). The decontamination factors of this procedure are above 4 × 10⁷ for barium and 4 × 10⁵ for molybdenum; the chemical yields of cesium are more than 85% for samples of less than 10 g. This method enables to separate cesium from large size of samples for the determination of ultralow level ¹³⁵Cs, avoiding the problem of removal of a huge amount of Mo in the dissolved AMP. Intrinsic ¹³⁷Cs in the environmental samples measured by gamma spectrometry before and after separation was used as internal isotope dilution standard for quantitative determination of ¹³⁵Cs without complete release and recover of radiocesium. The interference of barium (¹³⁵Ba and ¹³⁷Ba) to the ICP-MS measurement of ¹³⁵Cs and ¹³⁷Cs was further suppressed to 8 × 10^-5 by using N₂O as the reaction gas in ICP-MS/MS at a flow rate of 0.7 mL/min, so a total suppression of 2 × 10^-12 for Ba was achieved, making the isobaric interference of Ba isotopes to the measurement of ¹³⁵Cs and ¹³⁷Cs in environmental samples negligible. A detection limit of 9.1 × 10^-17 g/g for ¹³⁵Cs and ¹³⁷Cs was achieved for 60 g samples. The developed method was validated by analysis of standard reference materials (IAEA-375, IAEA-330, and IAEA-385) and successfully applied for the determination of ¹³⁵Cs concentrations and ¹³⁵Cs/¹³⁷Cs ratios in soil samples collected from Denmark, Sweden, and Ukraine. The ¹³⁵Cs/¹³⁷Cs isotopic ratios in Danish soil (2.08-2.68) were significantly higher than that from Sweden and Ukraine (0.65-0.71), indicating different sources of radiocesium. This work demonstrated the application of ¹³⁵Cs/¹³⁷Cs as a unique fingerprint for discriminating the sources of radioactive contamination and estimating their contribution to the total inventory, which will be useful for nuclear forensics and environmental tracer studies.

Distribution and budget of 137Cs in the China Seas

Cesium-137 is one of the most abundant anthropogenic radionuclides released by atmospheric nuclear testing and nuclear accidents, and accordingly it may significantly impact the health of humans and marine environmental eco-systems. Documenting the distribution and inventory of 137Cs is thus a crucial task. In this study, we collected a large number of datasets with field observations of 137Cs in the China Seas, in order to provide an in-depth understanding of 137Cs budgets and distributions. The activity and inventory of 137Cs in China Seas' sediments showed large spatial variations, related to the 137Cs source, sedimentation rates and the mineral composition of sediments. The 137Cs concentration in sediments decreased with distance from the shore, generally tracing the distribution of sedimentation rates. High 137Cs inventories in the water column indicated a high solubility and long mean residence times. The mean residence times of 137Cs in the China Seas were determined to be 45.6 ± 3.8 years for the South China Sea (SCS), 36.8 ± 3.1 years for the East China Sea (ECS), and 12.0 ± 1.0 years for the Yellow Sea (YS). A 137Cs mass balance suggests that oceanic input from the north Pacific is the dominant 137Cs source to the China Seas, contributing about 96.9% of this substance. Furthermore, the bulk of 137Cs remains dissolved in the SCS water column, while 137Cs is mostly deposited to the sediments of the ECS and the YS. This new compilation of the activity level and inventory of 137Cs help to establish background levels for future 137Cs studies in the China Seas.

Determination of Ultratrace Level 135Cs and 135Cs/137Cs Ratio in Small Volume Seawater by Chemical Separation and Thermal Ionization Mass Spectrometry

The atomic ratio of ¹³⁵Cs/¹³⁷Cs is a powerful fingerprint for distinguishing the source terms of radioactive contamination and tracing the circulation of water masses in the ocean. However, the determination of the ¹³⁵Cs/¹³⁷Cs ratio is very difficult due to the ultratrace level of ¹³⁵Cs (<0.02 mBq/m³) and ¹³⁷Cs (<2 Bq/m³) in the ordinary seawater samples. In this work, a sensitive method was developed for determination of ¹³⁵Cs concentration and ¹³⁵Cs/¹³⁷Cs ratio in seawater using chemical separation combined with thermal ionization mass spectrometry (TIMS) measurement. Cesium was first preconcentrated from seawater using ammonium molybdophosphate-polyacrylonitrile column chromatography and then purified using cation exchange chromatography to remove the interferences. With this method, decontamination factors of 6.0 × 10⁶ for barium and 1800 for rubidium and a chemical yield of more than 60% for cesium were achieved. By using glucose as an activator, the ionization efficiency of cesium was significantly improved to 50.6%, and a constant high current of Cs⁺ (20 V) can be maintained for more than 180 min, which ensures sensitive and reliable measurement of low level ¹³⁵Cs and ¹³⁷Cs. Detection limits of 4.0 × 10^-17 g/L for both ¹³⁵Cs and ¹³⁷Cs for 200 mL seawater were achieved, which enables the accurate determination of ¹³⁵Cs concentration and ¹³⁵Cs/¹³⁷Cs ratio in a small volume of seawater samples (<200 mL). The developed method has been validated by analysis of seawater reference material IAEA-443. Seawater samples collected from the Greenland Sea, Baltic Sea, and Danish Straits have been successfully analyzed for ¹³⁵Cs concentrations and ¹³⁵Cs/¹³⁷Cs ratios, and the results showed that ¹³⁵Cs concentrations in the seawater of the Baltic Sea is much higher than that in the Greenland Sea, which is attributed to the high deposition of Chernobyl accident derived radiocesium in the Baltic Sea region.

Direct Quantitation of 135Cs in Spent Cs Adsorbent Used for the Decontamination of Radiocesium-Containing Water by Laser Ablation Inductively Coupled Plasma Mass Spectrometry

The long-term safety assessment of spent Cs adsorbents produced during the decontamination of radiocesium-containing water at the Fukushima Daiichi nuclear power plant requires one to estimate their ¹³⁵Cs content prior to final disposal. ¹³⁵Cs is usually quantified by inductively coupled plasma mass spectrometry (ICP-MS), which necessitates the elution of Cs from Cs adsorbents. However, this approach suffers from the high radiation dose from ¹³⁷Cs that is present in the contaminated water and Cs adsorption irreversibility. To address these challenges, we herein employed laser ablation ICP-MS for direct quantitation of ¹³⁵Cs in Cs adsorbents and used a model Cs adsorbent prepared by immersion of a commercially available Cs adsorbent into radiocesium-containing liquid waste to verify the developed technique. Crushing and subsequent coating with a nitrocellulose-based curing agent provided a thin flat surface and thus allowed for stable solid sampling during laser ablation. The use of the ¹³⁵Cs/¹³⁷Cs ratio and ¹³⁷Cs radioactivity obtained by gamma spectrometry achieved simple and precise quantitation of ¹³⁵Cs. The obtained ¹³⁵Cs/¹³⁷Cs ratio of 0.41 ± 0.02 well agreed with that obtained for the original liquid waste sample by solution nebulization measurements, and the proposed method was concluded to be suitable for large-scale ¹³⁵Cs quantitation, requiring only very small (<10 mg) samples with total ¹³⁷Cs radioactivity.

Acute and late effects of combined internal and external radiation exposures on the hematopoietic system

Purpose: Incidents, such as nuclear facility accidents and the release of a 'dirty bomb', might result in not only external irradiation of personnel, but additional internal exposures through concomitant inhalation and/or ingestion of radioactive particulates. The purpose of this study was to define the impact of such a combination of radiation injuries on the hematopoietic niche.Material and methods: To assess changes in the murine hematopoietic system, we used a combined exposure of total body irradiation (TBI, 6 Gy) followed immediately by an internal (intraperitoneal) administration of 100 µCi of soluble ¹³⁷Cs. We then evaluated acute survival in combined versus single modality exposure groups, as well as assessing hematopoietic function at 12 and 26 week time points.Results: Acutely, the combination of external and internal exposures led to an unexpected delay in excretion of ¹³⁷Cs, increasing the absorbed dose in the combined exposure group and leading to mortality from an acute hematopoietic syndrome. At 12 weeks, all exposure paradigms resulted in decreased numbers of phenotypic hematopoietic stem cells (HSCs), particularly the short-term HSCs (ST-HSC); long-term HSCs (LT-HSC) were depleted only in the internal and combined exposure groups. At 26 weeks, there was significant anemia in both the TBI alone and combined exposure groups. There were decreased numbers in both the LT- and ST-HSCs and decreased functionality, as measured by competitive repopulation, was seen in all radiation groups, with the greatest effects seen in the internal and combined exposure groups.Conclusions: Our data indicate that a combined injury of sublethal external irradiation with internal contamination induces significant and persistent changes in the hematopoietic system, as may have been predicted from the literature and our own group's findings. However, a novel observation was that the combined exposure led to an alteration in the excretion kinetics of the internal contamination, increasing the acute effects beyond those anticipated. As a result, we believe that a combined exposure poses a unique challenge to the medical community during both the acute and, possibly, delayed recovery stages.

Quantitative determination of total cesium in highly active liquid waste by using liquid electrode plasma optical emission spectrometry

A sensitive analytical method for determination of total cesium (Cs) in highly active liquid waste (HALW) by using modified liquid electrode plasma optical emission spectrometry (LEP-OES) is developed in this study. The instrument is modified to measure radioactive samples in a glove box. The effects of important factors, including pulsed voltage sequence and nitric acid concentration, on the emission of Cs are investigated. The limit of detection (LOD) and limit of quantification (LOQ) are 0.005 mg/L and 0.02 mg/L, respectively. The achieved LOD is one order lower than that of recently developed spectroscopic methods using liquid discharge plasma. The developed method is validated by subjecting a simulated HALW sample to inductively coupled plasma mass spectrometry (ICP-MS). The recoveries obtained from a spike-and-recovery test are 96-102%, implying good accuracy. The method is successfully applied to the quantification of Cs in a real HALW sample at the Tokai reprocessing plant in Japan. Apart from dilution and filtration of the HALW sample, no other pre-treatment process is required. The results agree well with the values obtained using gamma spectrometry. The developed method offers a reliable technique for rapid analysis of total Cs in HALW samples.

Stable and radioactive cesium: A review about distribution in the environment, uptake and translocation in plants, plant reactions and plants' potential for bioremediation

Radiocesium in water, soil, and air represents a severe threat to human health and the environment. It either acts directly on living organisms from external sources, or it becomes incorporated through the food chain, or both. Plants are at the base of the food chain; it is therefore essential to understand the mechanisms of plants for cesium retention and uptake. In this review we summarize investigations about sources of stable and radioactive cesium in the environment and harmful effects caused by internal and external exposure of plants to radiocesium. Uptake of cesium into cells occurs through molecular mechanisms such as potassium and calcium transporters in the plasma membrane. In soil, bioavailability of cesium depends on the chemical composition of the soil and physical factors such as pH, temperature and tilling as well as on environmental factors such as soil microorganisms. Uptake of cesium occurs also from air through interception and absorption on leaves and from water through the whole submerged surface. We reviewed information about reducing cesium in the vegetation by loss processes, and we extracted transfer factors from the available literature and give an overview over the uptake capacities of 72 plants for cesium from the substratum to the biomass. Plants with high uptake potential could be used to remediate soil and water from radiocesium by accumulation and rhizofiltration. Inside plants, cesium distributes fast between the different plant organs and cells, but cesium in soil is extremely stable and remains for decades in the rhizosphere. Monitoring of contaminated soil therefore has to continue for many decades, and edible plants grown on such soil must continuously be monitored.

Selective sorption of uranium from aqueous solution by graphene oxide-modified materials

The effect of competing ions on the sorption behaviour of uranium onto carboxyl-functionalised graphene oxide (COOH-GO) were studied in batch experiments in comparison to graphene oxide (GO) and graphite. The effect of increasing the abundance of select chemical functional groups, such as carboxyl groups, on the selectivity of U sorption was investigated. In the course of the study, COOH-GO demonstrated superior performance as a sorbent material for the selective removal of uranyl ions from aqueous solution with a distribution coefficient of 3.72 ± 0.19 × 10³ mL g⁻¹ in comparison to 3.97 ± 0.5 × 10² and 2.68 ± 0.2 × 10² mL g⁻¹ for GO and graphite, respectively.

Studies on Isotope Ratio Measurement of Cl by Inductively Coupled Plasma Triple-quad Mass Spectrometry

Fundamental studies on isotope ratio measurement of Cl were carried out using inductively coupled plasma triple-quad mass spectrometry (ICP-MS/MS) and the analytical performance obtained was compared to that obtained by ICP sector field mass spectrometer (ICP-SFMS). Though the polyatomic ion interferences of ¹⁶O¹⁸O¹H and ³⁶Ar¹H with respect to ³⁵Cl and ³⁷Cl, respectively, made a negative effect on the accuracy and the precision for isotope ratio measurements of Cl, the ICP-SFMS could eliminate these interferences by medium mass resolution mode (m/Δm = 4000) and achieved the isotope ratio measurements with 0.2 - 0.5% of relative standard deviation (RSD) at the concentrations of Cl from 1 to 10 mg kg^-1. In the case of ICP-MS/MS, both the single-MS mode without collision reaction gas and the MS/MS mode with collision reaction gases such as oxygen (O₂) and hydrogen (H₂) were examined and compared their analytical sensitivities as well as the precisions of isotope ratio measurement of Cl. The precisions of Cl isotope ratio measurements were 3 - 14% of RSD at the concentrations of Cl from 5 to 100 mg kg^-1, when single-MS mode was carried out, even though the similar isotope ratios of ³⁵Cl/³⁷Cl could be obtained. In the case of O₂ gas for MS/MS mode with mass-shift method, precisions of 0.3 - 2% of RSD were obtained at the concentration range of 1 - 100 mg kg^-1. In the case of H₂ gas, similar sensitivities as those obtained by ICP-SFMS and the precisions of 0.2 - 0.5% of RSD at the concentration range of 1 - 10 mg kg^-1 were obtained. From these results, it was evaluated that the ICP-MS/MS in MS/MS mode with collision reaction gas could be used for Cl isotope ratio measurements for such studies as stable isotope tracers, isotope abundance measurements in nuclear chemistry and accurate determinations by isotope dilution mass spectrometry.

Simultaneous determination of radiocesium ((135)Cs, (137)Cs) and plutonium ((239)Pu, (240)Pu) isotopes in river suspended particles by ICP-MS/MS and SF-ICP-MS

Due to radioisotope releases in the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, long-term monitoring of radiocesium ((135)Cs and (137)Cs) and Pu isotopes ((239)Pu and (240)Pu) in river suspended particles is necessary to study the transport and fate of these long-lived radioisotopes in the land-ocean system. However, it is expensive and technically difficult to collect samples of suspended particles from river and ocean. Thus, simultaneous determination of multi-radionuclides remains as a challenging topic. In this study, for the first time, we report an analytical method for simultaneous determination of radiocesium and Pu isotopes in suspended particles with small sample size (1-2g). Radiocesium and Pu were sequentially pre-concentrated using ammonium molybdophosphate and ferric hydroxide co-precipitation, respectively. After the two-stage ion-exchange chromatography separation from the matrix elements, radiocesium and Pu isotopes were finally determined by ICP-MS/MS and SF-ICP-MS, respectively. The interfering elements of U ((238)U(1)H(+) and (238)U(2)H(+) for (239)Pu and (240)Pu, respectively) and Ba ((135)Ba(+) and (137)Ba(+) for (135)Cs and (137)Cs, respectively) were sufficiently removed with the decontamination factors of 1-8×10(6) and 1×10(4), respectively, with the developed method. Soil reference materials were utilized for method validation, and the obtained (135)Cs/(137)Cs and (240)Pu/(239)Pu atom ratios, and (239+240)Pu activities showed a good agreement with the certified/information values. In addition, the developed method was applied to analyze radiocesium and Pu in the suspended particles of land water samples collected from Fukushima Prefecture after the FDNPP accident. The (135)Cs/(137)Cs atom ratios (0.329-0.391) and (137)Cs activities (23.4-152Bq/g) suggested radiocesium contamination of the suspended particles mainly originated from the accident-released radioactive contaminates, while similar Pu contamination of suspended particles caused by the accident could be neglected as the (240)Pu/(239)Pu atom ratios (0.182-0.208) were within the range of global fallout.

(135)Cs/(137)Cs isotopic composition of environmental samples across Europe: Environmental transport and source term emission applications

(135)Cs/(137)Cs isotopic analyses represent an important tool for studying the fate and transport of radiocesium in the environment; in this work the (135)Cs/(137)Cs isotopic composition in environmental samples taken from across Europe is reported. Surface soil and vegetation samples from western Russia, Ukraine, Austria, and Hungary show consistent aged thermal fission product (135)Cs/(137)Cs isotope ratios of 0.58 ± 0.01 (age corrected to 1/1/15), with the exception of one sample of soil-moss from Hungary which shows an elevated (135)Cs/(137)Cs ratio of 1.78 ± 0.12. With the exception of the outlier sample from Hungary, surface soil/vegetation data are in quantitative agreement with values previously reported for soils within the Chernobyl exclusion zone, suggesting that radiocesium at these locations is primarily composed of homogenous airborne deposition from Chernobyl. Seawater samples taken from the Irish Sea show (135)Cs/(137)Cs isotope ratios of 1.22 ± 0.11 (age corrected to 1/1/15), suggesting aged thermal fission product Cs discharged from Sellafield. The differences in (135)Cs/(137)Cs isotope ratios between Sellafield, Chernobyl, and global nuclear weapons testing fallout indicate that (135)Cs/(137)Cs isotope ratios can be utilized to discriminate between and track radiocesium transport from different nuclear production source terms, including major emission sources in Europe.