Uranium ore concentrate (UOC) is a group of intermediate products widely used in the nuclear fuel cycle. Following the recent characterisation and classification of UOC industrial product powders for nuclear forensic analysis, this paper presents an experimental study of the hygroscopic properties of these UOC stockpile samples for long-term storage and the inhalation risk assessment of uranium particles. Two independent techniques, the density balance and Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), were utilised to measure increases in sample weight and the infrared absorption peak of ten UOC samples, respectively, due to hygroscopic growth. Taking (NH4)4((UO2)2(SO4)O2)2(H2O) powder as an example, the hygroscopicity mechanism was investigated experimentally by monitoring hydration and dehydration processes using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and Thermogravimetric-Differential Thermal Analysis (TG-DTA), respectively. The hygroscopic growth factor of (NH4)4((UO2)2(SO4)O2)2(H2O) sample was determined using the above two techniques under precisely controlled temperature and humidity conditions. Screening results show significant differences in the hygroscopicity of sodium- and ammonium-containing UOC powders, despite their similar elemental composition, infrared functional groups, and crystal structures. The porous surface and hygroscopic component are beneficial for hygroscopic growth. Observation of the hydration and dehydration process confirms that the physical adsorption of water is the dominant mechanism. The hygroscopic growth factors of sample mass and infrared absorption peak increase with rising relative humidity above 80% RH. The hygroscopic growth curve of (NH4)4((UO2)2(SO4)O2)2(H2O) powder could be described using a simplified κ-Köhler equation. A dense surface, low RH (<80%) and an inert buffer gas are recommended for material processing and stable storage. For (NH4)4((UO2)2(SO4)O2)2(H2O) particles possibly inhaled in the respiratory tract, the effect of hygroscopic growth on the deposition profile is also discussed.

This work details technical advancements in multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for high-precision plutonium (Pu) isotope ratio analysis. Uranium (U) and Pu isotopes have been proven to exhibit similar mass fractionation effects, as measured using MC-ICP-MS, within analytical uncertainty. Herein, 233U-236U double spike method with IRMM3636 was developed to correct the mass fractionation while measuring Pu isotope measurement, achieving an RSD% of 0.0029 % for Pu isotope ratios at 10-2 level. This method was the first one to precisely measure low-abundance isotopes such as 241Pu and 242Pu via combining Faraday cup (1013 Omega amplifier) and secondary electron multiplier detector configuration. At trace levels (ng), long-term RSDs of 239Pu at a laboratory working standard reached 0.019 % (241Pu/239Pu) and 0.046 % (242Pu/239Pu) near the 10- 4 level, demonstrating exceptionally high precision in the isotope ratio analysis and representing the highest precision reported to date for these ratios. This state-of-the-art method maintained high sample throughput while delivering exceptional accuracy. Its robustness was confirmed through successful application to Pu isotope analysis in irradiated nuclear fuel samples, highlighting its broad applicability.

Despite the ecological and geochemical importance of coastal and estuarine ecosystems, the continental inputs and anthropogenic emissions of trace elements in their global marine budgets are not well constrained due to a lack of comprehensive and inclusive assessment of diverse sources. Here, we investigated two small but representative rivers (Las and Eygoutier) of the Mediterranean Sea to determine the contributions of rare earth elements (REEs) from terrestrial loadings, atmospheric depositions, and anthropogenic emissions within the watersheds and Toulon Bay (France). Both the dissolved and particulate loadings of the rivers significantly increased during intermittent flood conditions relative to base flow. The flow-weighted mean concentrations of dissolved Nd (as a representative REE) ranged from 29 ± 6 and 41 ± 16 ng L-1 for the two rivers repectively, while the time-weighted mean particulate concentrations (TWMC) were 8.0 ± 3.4 and 18.8 ± 6.3 mg kg-1. Similarly, TWMCs of atmospheric depositions were 13.3 ± 1.8 and 23.7 ± 4.0 mg kg-1 for dry and wet conditions. Atmospheric depositions and fluvial particulate loadings are the primary input and output within the watershed, while river dissolved fluxes, porewater diffusion, and atmospheric depositions are the primary external sources of Nd to the water column. Furthermore, we observed significant La anomalies in the dissolved and atmospheric fractions while the discharge of treated wastewater is a significant REE input to the bay, marked by Tb anomalies. Overall, these results suggest considering small but typical rivers, rather than focusing solely on major fluvial systems, to gain a more comprehensive understanding of the transport and fate of REEs at the continent-to-ocean interface.

Uranium ore concentrates(UOCs) are a kind of nuclear materials which can be traded legally in the international market. Uranium ore concentrates have become attractive targets for nuclear forensic because of the richness in characteristic signatures compared to other materials produced later in the fuel cycle. The rich trace impurities of UOCs is an ideal object for nuclear forensic analysis，in which it reflects the important information of uranium ore formation, mineral composition, process of uranium mining and geolocation. As one of the important characteristic fingerprints, the rare earth elements(REEs) distribution pattern of UOCs can be used as an attractive alternative to attribute the origin of uranium ore concentrates. In this paper, several multivariate statistical methods in pattern recognition, including principal component analysis(PCA), factor analysis(FA), cluster analysis(CA) and partial least squares(PLS) were compared and the advantages and disadvantages of various methods were summarized. The results show that it is a tough work to fully describe the characteristic fingerprint parameters of uranium ore concentrates by only one or two methods. The principal component analysis(PCA) method can reduce the dimension of the data and retain the original characteristics of the data. However, the classification of the data is not taken into account in the process of analysis and the results only show the difference between the samples. The factor analysis(FA) method is essentially a process of extracting potential factors from dominant variables and the form of factors is not unique. Cluster analysis(CA) can classify the origin of uranium ore concentrates. However, there is no quantitative data to illustrate the difference in the same classification of uranium ore concentrates. The partial least squares(PLS) method takes into account the difference between all the data points from the algorithm, and PLS can also perform multiple iterations to identify the subtle difference of uranium ore and uranium ore concentrates with the same origin, so that the precise geolocation of uranium ore concentrate can be realized. It is generally used in regression studies with less sample size, so PLS can show more detailed fingerprint features than PCA. To date, the scientists still face a great of difficulties to attribute the geolocation of uranium ore concentrates, especially to those uranium ore concentrates mined and milled in the countries or regions with vast territory and complex geological features. The combination of several multivariate statistical methods might be an attractive avenue to accurately and effectively trace the origin of uranium ore concentrates, but it still has a long way to go.

Accurate determination of Am-242m is critical for nuclear forensics and environmental radioisotope monitoring. To achieve high sensitivity in analyzing ultra-trace Am-242m using mass spectrometry, it is imperative to eliminate interferences such as isobars, polyatomic ions, and bulk matrices. In this investigation, we developed a three-step chromatographic method utilizing TRU resin, NaBiO3, and HDEHP resin based on the adsorption characteristics of the target elements and optimization of column conditions. Validation experiments demonstrated the thorough removal of interfering elements with high decontamination factors (DF), notably achieving a DF value of 1.4 x 10(4) for Cm. The method is robust and suitable for sample preparation to accurately quantify ultra-trace Am-242m in complex samples.

-This work studies effective methods for producing 225Ac and 223Ra by bombarding 232Th and natural uranium targets with different incident particles. Direct production of 225Ac via high-energy proton bombardment of 232Th inevitably contains 227Ac impurities, complicating the separation and purification processes. In contrast, obtaining 225Ac through the generated 225Ra can avoid 227Ac contamination. Given the low cross section for the proton-thorium reaction to produce 225Ra, exploring new methods to improve 225Ra production efficiency is critical. This study utilized several physical models of the Monte Carlo transport codes FLUKA and PHITS to calculate the production cross sections of 225Ac, 225Ra, 223Ra, and 227Th via the bombardment of thorium and uranium targets with energetic protons, α-particles, 9Be, and 12C across an energy range of 10-800 MeV/u. The predicted cross sections were then compared with existing experimental data. The predictions indicate that the energy thresholds to produce 225Ac, 225Ra, and 223Ra via α-particle and heavy ion irradiation are lower than those for proton, and the production cross sections are significantly increased, the incident energy corresponding to the peak cross section is mainly below 100 MeV/u. According to the PHITS JQMD-2.0 results, using α-particle bombardment of thorium targets to produce 225Ra and subsequently obtaining high-purity 225Ac may be an efficient production pathway. Moreover, when the α-particle energy is below 100 MeV/u, the predicted cross section of 225Ra for the natural uranium target is higher than that for the thorium target, suggesting that α-particle bombardment of the natural uranium target could be a potential new method to improve 225Ac production efficiency. This study provides theoretical reference for subsequent experimental cross section measurement and isotope production.

A novel approach was developed for the precise analysis of the 238Pu/239Pu ratio in plutonium using thermal ionization mass spectrometry (TIMS). This methodology was based on the difference in thermal evaporation behavior between U and Pu during the total evaporation (TE) process. By incorporating the U interference indicator into the Pu solution, a linear model that related the m/z 238 a.m.u. intensity changes to the isotope ratios of 238Pu/239Pu and 238U/235U was established. The ratios of 238Pu/239Pu and 238U/235U was determined by fitting the experimental data using multiple linear regression analysis. This method had been applied to analyze laboratory isotopic standard samples Pu(SO4)2.4H2O. Results showed that, even with extremely small sample size of 238Pu (picogram level), the relative standard deviation of 238Pu/239Pu ratio was less than 0.2 %. The approach was simple and would be an effective tool as a method for the characterization of 238Pu using TIMS.

Uncovering the nature of dark matter microscopic particles is one of the most important disciplinary goals of physics and astronomy in the 21st century, and how to reduce background signals and environmental interference in dark matter experiments is one of the key factors to improve the sensitivity of the detector and to take the lead in obtaining significant detection results. High-purity nitrogen, as a crucial gas for detector purging, scintillator purification and pipe cleaning, among other things, contains the radioactive gases 85Kr and 81Kr in natural Kr, which emit beta-rays that can interfere with the detection of dark matter signals. Therefore, it is necessary to measure the concentration of ultra-trace level Kr in high-purity nitrogen, and screen high-purity nitrogen complying with the standard for use in dark matter experiments. This study develops a novel analytical method to determine ultra-trace level Kr in high-purity nitrogen using a static noble gas mass spectrometer coupled with a newly designed sample processing system. A large amount of reactive gases from the original sample are removed by the large-volume high-temperature purification device, and then we explore a simple and iterative trapping method for Ar-Kr separation. This method improves the noble gas separation factor with the promise of ensuring recovery. The separated Kr is fed into a static vacuum mass spectrometer. The detection limit of this method for natural Kr is as low as 10-14 L L-1 with an uncertainty of about 8%. This paper has developed newly an sample processing system combined with a static vacuum mass spectrometer to study how to measure 10-12 level krypton in high-purity nitrogen.

Precise and accurate analysis of 235U/238U, 234U/238U, 230Th/234U and 230Th/232Th in 15 uranium ore concentrates (UOCs) was achieved using ICP-MS for nuclear forensic applications. A novel method was developed to dating UOCs.

The marine chemistry of platinum group elements is poorly documented despite robust evidence of their widespread emissions and deposition around the globe. Here, we report the concentrations and discuss the geochemical behaviours of Ag, Pd and other trace and ultra-trace elements in the Estuary and Gulf of St. Lawrence (EGSL). We highlight the contrasting mixing behaviours of these elements, i.e., conservative (Cd, Re) vs. non-conservative (Ag, Pd), in samples collected during the winter and ice-covered conditions. We ascribe the contrasting geochemical behaviour of these elements to their differential affinity for reactive surfaces carried into the estuary from the frozen watersheds. We also report an increase of the concentrations of Ag (up to 40 pmol L-1), Pd (up to 10 pmol L-1) and Pt (up to 0.4 pmol L-1) in the bottom and oxygen-depleted waters of the Gulf of St. Lawrence (GSL). A strong correlation between dissolved Pt concentrations and the stable carbon isotopic composition of the dissolved inorganic carbon (δ13C-DIC) suggests that the increased mobility of Pt may result from the aerobic mineralization of organic carbon or the oxidation of Pt-bearing organic complexes. Molar Pt/Pd ratios in the three water masses that compose the water column in the EGSL highlight a potential influence of anthropogenic sources near urban centers. The signature of continental end-members will be required to confirm the impacts of road traffic on the estuarine geochemistry of these elements.

Rare earth elements (REEs) constitute a key group of critical minerals that are strategic for the global low-carbon economy and several United Nations Sustainable Development Goals. Their expected escalating emissions into the environment from emerging anthropogenic sources can negatively affect natural ecosystems. However, their hormetic effects make these elements effective fertilizers to promote crop production. Here, we investigate the response of tomatoes and ferns to REE exposure (La, Gd, Yb). While ferns were unresponsive to REEs, these elements promote evident benefits in tomatoes, e.g., elevating nutrient uptake, higher photosynthetic capacity and phytohormone enhancement to allocate energy to green tissue and root development. Nevertheless, the non-selective cation uptake incurs risks of accumulating non-essential elements in edible tissues. These evident benefits of REEs on crops support applications in agricultural production systems, create added value to the global distribution and promote better material flow management of REEs as strategic and critical resources.

The evolution of early life is intimately related to environmental changes on Earth, and in particular, the accumulation of oxygen in the atmosphere and oceans. However, the record of environmental O2 abundance in the middle to late Proterozoic Eon, during which many new eukaryotic lineages emerged, is sparse and controversial. Here we present a uranium (U) isotope record from late Proterozoic shales from northwestern Canada, Arctic Canada (Baffin Island), Svalbard, and Greenland, coupled with a novel approach for inferring authigenic U isotope values (δ238Uauthigenic). A compilation comprising our new data and available literature data (854 δ238Uauthigenic values) through geologic time indicates a consistent rise in δ238Uauthigenic values following the Great Oxidation Event. This gradual increase in δ238U can be interpreted as an increase in the frequency of transient oxygenation events and also as a variation of U isotope fractionation factors between authigenic uptake and seawater (Δ238U) associated with different redox conditions occurring over the Earth's history. In conjunction with the U isotopic signature, we used previously published Fe speciation data from our samples to infer local controls on U incorporation and isotopic fractionation. The results suggest that late Proterozoic oceans were dominantly ferruginous, punctuated by periods of transient oxygenation. During these transient oxic conditions, high U isotope fractionation resulted in Δ238U values as high as ~1.2‰ relative to the δ238Ucrust. However, under ferruginous conditions, smaller isotopic fractionation led to Δ238U values <0.6‰. Integrating conclusions from our study with other geochemical studies suggests the occurrence of several spatially localized oxygenation events across the globe during the late Proterozoic. These conclusions help to better integrate geochemical and fossil records in the context of early evolution of complex life.

The global shift toward green energy alternatives escalates demands for new resources, including rare earth elements (REEs), as per their implications in various green innovations. However, our understanding of their environmental cycle, especially the interactions with aquatic organisms, remains deficient, ultimately hindering environmental protection efforts. Here, we investigate the accumulation of REEs and 18 other elements in bulk and sorted plankton collected with different net mesh sizes (30, 63, 200, 333, 500 μm) in the Estuary and Gulf of St. Lawrence in the summer and winter of 2020. We observed significant correlations between the concentrations of REEs and elements of different charge numbers and ionic radii (Ba, Co, Cs, Fe, Mn, Pb, Rb and V), indicating non-selective uptake of REEs into plankton. All these elements have their highest concentrations in the fluvial corridor and upper estuary, with more significant enrichment in phytoplankton ([La] = 26.4 ± 4.8 mg kg-1) than zooplankton ([La] = 11.6 ± 8.3 mg kg-1). Their concentrations decrease to the minimum in the Gulf of St. Lawrence, especially in zooplankton ([La] = 4.8 × 10-2 ± 3.2 × 10-2 mg kg-1). We also assessed REE patterns to identify differential REE fractionation processes and anomalies. The freshwater plankton exhibits enrichment of middle REEs (MREEs) relative to the light and heavy REEs (LREEs and HREEs), potentially because of the higher binding affinity of MREEs on cellular surface transporters and metal loading effects. In estuarine and marine settings, the REE patterns in biological samples align with suspended particles, exhibiting a linear trend with LREE enrichment. This process is more noticeable in sorted macrozooplankton, which have significant Eu anomalies (Eu/Eu* up to 2), indicating differential incorporation of REEs into the chitin shells. This study highlights the significant enrichment of REEs into freshwater primary producers and the accumulation pathway similar to other inorganic elements.

We report a simple chemical separation method (i.e., single column and single elution) using an anion exchange resin (1-X8) to quantify Re and four co-eluted elements (Ag, Cd, Pd, Zn) from fresh and seawater matrices.

The marine chemistry of platinum is poorly understood, and its oceanic budget remains unconstrained, mainly because of severe analytical artifacts and the paucity of studies on this element of increasing technological interest. Here, we report dissolved and acid-leachable Pt concentrations in the Estuary and Gulf of St. Lawrence (EGSL) under winter conditions, and relate its estuarine geochemical behaviour to that of Cd, an element with similar characteristics and for which we have a more comprehensive knowledge. In contrast to Cd and to most pristine river systems, dissolved Pt concentrations in the EGSL in the winter (0.46 +/- 0.09 pM) are significantly higher than the marine endmember (0.26 +/- 0.06 pM). This discrepancy could be ascribed to the geology of the EGSL's drainage basins as well as the wet deposition of atmospheric Pt. This observation draws attention to the impacts of anthropogenic Pt emissions on its environmental dispersion, background estuarine concentrations and processes, especially in high-latitude regions. Unlike the results of most studies carried out in estuarine systems under ice-free conditions, we observed a near-conservative mixing behaviour of Pt and Cd in the surface waters of the EGSL during the winter, as is the case for dissolved Mn, Fe and rare earth elements. This observation could be explained by a decreased delivery of colloidal and organic materials to the estuary under ice-covered conditions. We also observed that dissolved Pt and Cd concentrations increase in the bottom waters of the EGSL, where the waters are more saline and oxygen-depleted. These higher concentrations may originate from aerobic mineralization of Pt-bearing organic matter, a decrease of Pt-reactive surface sites on suspended particles, and a change in redox speciation of PtII into PtIV. Overall, these results highlight that winter and oxygen-depleted conditions can amplify continental Pt fluxes to the oceans and thus should be considered in future Pt oceanic budget calculations.

Rare Earth Elements, including the lanthanide series and Y (REYs), are important tracers and paleo-proxies of biogeochemical processes, water mass transport and oceanic mixing. At the interface between the continents and oceans, the geochemical behaviour of REYs in estuarine environments is generally described as being non-conservative, with large-scale removal by particle scavenging. This conventional interpretation stems from observations carried out in tropical or sub-tropical estuaries. However, major river systems in the mid- and high latitude regions are subjected to winter conditions when a frozen watershed and an ice cover may affect the continental input of particles and the REY geochemistry. Here, we investigate the geochemical behaviour of REYs in the Estuary and Gulf of St. Lawrence (EGSL) in spring 2003 as well as winter and summer 2020. In contrast to the ice-free seasons, REYs and Fe behave conservatively in the estuary during the winter. In addition, we observed a higher REY affinity toward particle surfaces and fractionation in REE patterns in the hypoxic deep waters of the estuary. The latter observation may reflect enhanced REY sorption to mineral-carrier surfaces exposed upon the remineralization of organic coatings on settling particles and to manganese oxides of benthic origin. Computed partition coefficient (Kd) values and strong correlations between Y/Ho, Er/Nd and Ce anomalies with dissolved oxygen concentrations support this hypothesis. The estimated annual dissolved load of REYs from the EGSL to the ocean ranges from 0.4 to 75 tons per year, thus contributing significantly to the global marine budget. The global river loading of dissolved Nd to the ocean was also revised to 4000 tons per year based on data available for 21 river systems.

The ability to differentiate anthropogenic signatures from natural processes in complex hydrological systems is critical for environmental regulation perspectives, especially to curb pollution and implement effective water management strategies. Here, we report variations in the concentrations of 57 chemical variables, including nutrients, major, trace and ultra-trace elements, as well as the concentrations of Escherichia coli in different water masses along the St. Lawrence River-Estuary continuum. The constant ratios among major elements indicate consistent carbonate and silicate weathering processes in the drainage basins. We also suggest applying Ce anomalies to trace waters of low alkalinity and low complexing capacity as the dominance of Ce3+ free ion could promote Ce oxidation, and thus negative Ce anomalies. Furthermore, the positive Eu anomalies and elevated Tl concentrations could highlight the cation exchange processes on clay particles. In the fluvial and estuarine sections of the St. Lawrence System, we demonstrate significant contributions of wastewater discharge and discuss the suitability of several wastewater tracers, e.g., excess of B, Na, K, as well as Rb/Sr and Gd anomalies. We also highlight the inputs of several minor and trace elements (e.g., Mn, Fe, Cu, Co, Ni) from south-shore tributaries to the St. Lawrence System. However, the complex anthropogenic activities in the watersheds did not allow clear source partitioning. Finally, increased mixing of different river water masses upstream of Quebec City, together with the estuarine salt front and suspended sediments, are also responsible for releasing these minor and trace elements into the aquatic media. The results presented here help support further environmental actions to curb the emission of contaminants in the St. Lawrence System and provide more robust tracers of natural and anthropogenic processes in aquatic environments.

Inductively coupled plasma mass spectrometry (ICP-MS) has been becoming a competitive technique for the measurement of trace americium isotopes, but the isobaric and polyatomic ions interference (Pu-241, (PbCl)-Pb-206-Cl-35, (PbCl)-Pb-204-Cl-37, etc.) will deteriorate the analysis accuracy for soil and sediment samples with high concentration of interfering elements (e.g., Pb). This study developed a novel analysis method to determine Am-241 using ICP-MS with tandem quadrupoles and collision/reaction cell. The interference of isobaric and polyatomic ions was effectively removed by the mass filter of quadrupole and reactions with NH3, with the contribution efficiency of interfering elements at m/z 241 or 243 lower than 1 x 10(-8), and the measurement sensitivity in this mode relatively (1170 Mcps/(mg/L)) higher than in other modes. The detection limit of 0.091 fg/g for Am-241 was achieved, 3 times better than other types of ICP-MS (Q-ICP-MS, SF-ICP-MS, etc.). The collision focusing by He and the chemical reaction with NH3 played an important role in the improvement of Am sensitivity and elimination of polyatomic ions. This study suggested that the presence of Cl- could significantly increase the polyatomic ions interference ((PbCl)-Pb-206-Cl-35, (PbCl)-Pb-204-Cl-37, (PbCl)-Pb-208-Cl-35, (PbCl)-Pb-206-Cl-37, etc.) because of the high Pb concentration in the soil or sediment samples, and thus should be completely removed. The developed method had been validated with two certified reference materials of soil (IAEA-375 and IAEA-Soil-6) and successfully applied to measure Am-241 concentrations in seven soil samples collected in different regions of China and one sediment sample collected in Denmark.

Rare earth elements (REEs) and Y, or REYs, are commonly used as geochemical proxies for water chemistry, history of the continental crust and provenance studies. At the continent-ocean interface, the estuarine geochemistry of REYs is commonly thought to be driven by large-scale removal of the dissolved fraction. Consequently, contributions of river-borne dissolved REYs to the marine budget are assumed to represent a minor fraction of the total flux. Here, we report a significant release of dissolved REYs, together with a fractionation between light REEs, heavy REEs and Y, in the tropical mangrove estuaries of New Caledonia. These observations were associated with biogeochemical processes of the redox-dynamic mangrove system, rather than a possible contribution of REYs from a fresh groundwater source, based on stable water isotope compositions. These findings imply that tropical mangrove estuaries may act as a sizeable source of REYs to the ocean rather than buffer zones, at least for the dissolved fraction. We also extrapolated our data to compute the contributions of dissolved REY fluxes from the mangroves to global oceans. This preliminary calculation suggests that the mangrove system supplies 2.6-5% of global river-borne dissolved Nd, an REE with the most comprehensive mass balance. Therefore, given that the ocean mass budget of REYs remains unbalanced with fluxes missing on a global scale, considering the mangrove system as an input of oceanic mass balance models may help improve our understanding of the global distribution of REYs.