Chelonians (turtles, tortoises, and sea turtles; hereafter, turtles) inhabit a wide variety of ecosystems that are currently, or have the potential in the future to become, radioactively ...contaminated. Because they are long-lived, turtles may uniquely accumulate significant amounts of the radionuclides, especially those with long half-lives and are less environmentally mobile. Further, turtle shells are covered by scutes made of keratin. For many turtle taxa, each year, keratin grows sequentially creating annual growth rings or layers. Theoretically, analysis of these scute layers for radionuclides could provide a history of the radioactivity levels in the environment, yet there are few previously published studies focused on the dynamics of radionuclide intake in turtles. Using established biochemical and ecological principles, we developed an allometric-kinetic model to establish relationships between the radionuclide concentrations in turtles and the environment they inhabit. Specifically, we calculated Concentration Ratios (CRs – ratio of radionuclide concentration in the turtle divided by the concentration in the soil, sediment, or water) for long-lived radionuclides of uranium and plutonium for freshwater turtles, tortoises, and sea turtles. These CRs allowed prediction of environmental concentrations based on measured concentrations within turtles or vice-versa. We validated model-calculated CR values through comparison with published CR values for representative organisms, and the uncertainty in each of the model parameters was propagated through the CR calculation using Monte Carlo techniques. Results show an accuracy within a factor of three for most CR comparisons though the difference for plutonium was larger with a CR ratio of about 200 times for sea turtles, driven largely by the uncertainty of the solubility of plutonium in sea water.
•Long-lived turtles could accumulate significant amounts of environmental radionuclides.•We developed an allometric-kinetic model predicting radionuclide dynamics among turtles.•Model Concentration Ratios were compared to ratios for similar species and existing data.•Comparisons show general accuracy of the model and elucidate research needs.
Protection of the environment from radiation fundamentally relies on dose assessments for non-human biota. Many of these dose assessments use measured or predicted concentrations of radionuclides in ...soil or water combined with Concentration Ratios (CRs) to estimate whole body concentrations in animals and plants, yet there is a paucity of CR data relative to the vast number of potential taxa and radioactive contaminants in the environment and their taxon-specific ecosystems. Because there are many taxa each having very different behaviors and biology, and there are many possible bioavailable radionuclides, CRs have the potential to vary by orders-of-magnitude, as often seen in published data. Given the diversity of taxa, the International Commission on Radiological Protection (ICRP) has selected 12 non-human biota as reference animals and plants (RAPs), while the U.S. Department of Energy (DOE) uses the non-taxon specific categories of terrestrial, riparian, and aquatic animals. The question we examine here, in part, is: are these RAPs and categorizations sufficient to adequately protect all species given the broad diversity of animals in a region? To explore this question, we utilize an Allometric-Kinetic (A-K) model to calculate radionuclide-specific CRs for common animal classes, which are then further subcategorized into herbivores, omnivores, carnivores, and invertebrate detritivores. Comparisons in CRs among animal classes exhibited only small differences, but there was order of magnitude differences between herbivores, carnivores, and especially detritivores, for many radionuclides of interest. These findings suggest that the ICRP RAPs and the DOE categories are reasonable, but their accuracy could be improved by including sub-categories related to animal dietary ecology and biology. Finally, comparisons of A-K model predicted CR values to published CRs show order-of-magnitude variations, providing justification for additional studies of animal assimilation across radionuclides, environmental conditions, and animal classes.
•There is a paucity of data for concentration ratios relative to the vast number of potential taxa and radioactive contaminants in the environment and their taxon-specific ecosystems.•We used an Allometric-Kinetic (A-K) model was to calculate radionuclide-specific CRs for common animal classes, which were then further subcategorized into herbivores, omnivores, carnivores, and invertebrate detritivores.•Comparisons in CRs among animal classes exhibited only small differences, but there was order of magnitude differences between herbivores, carnivores, and especially detritivores, for many radionuclides of interest.•Findings suggest that the ICRP ROs and the DOE categories are reasonable, but their accuracy could be improved by including sub-categories related to animal dietary ecology and biology.•Comparisons of A-K model predicted CR values to published CRs show order-of-magnitude variations, providing justification for additional studies of animal assimilation across radionuclides, environmental conditions, and animal classes.
Uranium isotopic composition can provide valuable information about the history and provenance of a nuclear material; therefore, uranium isotopic analyses are frequently made in the nuclear ...forensics, safeguards, and environmental monitoring communities. These measurements have always presented challenges due to the extreme variability in the relative abundance between the major (235U, 238U) and minor (233U, 234U, 236U) isotopes of uranium. The recently developed ATONA (Atto- to Nano-Amp) amplification system paired with Faraday cup detectors has a large dynamic range and low noise floor making it ideal for measuring uranium isotopic ratios in materials of both natural and anthropogenic origin. A wide variety of certified reference materials were analyzed to investigate the utility of the ATONA amplification system for determining uranium isotopic composition in samples ranging from depleted to highly enriched. The ATONA amplifiers provide nearly an order of magnitude improvement in external reproducibility over 1011 Ω amplifiers when measuring the minor 234U/238U ratio in isotopically natural and depleted samples and when paired with a secondary electron multiplier can measure very low relative abundance uranium isotopes (i.e., 236U).
Meckel syndrome (MKS) is a ciliopathy characterized by encephalocele, cystic renal disease, liver fibrosis and polydactyly. An identifying feature of MKS1, one of six MKS-associated proteins, is the ...presence of a B9 domain of unknown function. Using phylogenetic analyses, we show that this domain occurs exclusively within a family of three proteins distributed widely in ciliated organisms. Consistent with a ciliary role, all Caenorhabditis elegans B9-domain-containing proteins, MKS-1 and MKS-1-related proteins 1 and 2 (MKSR-1, MKSR-2), localize to transition zones/basal bodies of sensory cilia. Their subcellular localization is largely co-dependent, pointing to a functional relationship between the proteins. This localization is evolutionarily conserved, because the human orthologues also localize to basal bodies, as well as cilia. As reported for MKS1, disrupting human MKSR1 or MKSR2 causes ciliogenesis defects. By contrast, single, double and triple C. elegans mks/mksr mutants do not display overt defects in ciliary structure, intraflagellar transport or chemosensation. However, we find genetic interactions between all double mks/mksr mutant combinations, manifesting as an increased lifespan phenotype, which is due to abnormal insulin-IGF-I signaling. Our findings therefore demonstrate functional interactions between a novel family of proteins associated with basal bodies or cilia, providing new insights into the molecular etiology of a pleiotropic human disorder.
Fission reactions result in Nd isotope decay products which alter Nd isotopic compositions measured in nuclear debris. Trinitite samples measured by MC-ICP-MS show perturbations of Nd isotopes ...relative to
142
Nd, the only isotope of Nd which is blocked from fission product decay. By measuring
144
Nd/
142
Nd and the total number of atoms of
142
Nd in the sample, it is possible to quantify the total number of fissions in nuclear debris, an important signature in post-detonation nuclear forensics.
This work demonstrates an analytical protocol for high precision Sm isotope analysis by thermal ionization mass spectrometry (TIMS) using a Pt activator. The method permits precise measurements of ...small aliquots (1–20 ng) of Sm on single Re filament using a modified static-total evaporation technique. This study represents the first attempt to use such protocols for Sm isotope analyses while reducing the loading size of Sm for TIMS. The method could potentially be deployed to study geological, meteorites and lunar samples containing low Sm concentrations, to monitor neutron irradiation exposure based on
149,150
Sm, or to measure Sm isotopic composition in other types of nuclear samples.
Particulate isotopic analysis in nuclear forensics has developed rapidly during the past two decades due to technical advances in determining the isotopic composition of individual particles. This ...paper introduces basic statistical concepts that can be applied by analysts to understand the importance of statistical adequacy when interpretating particle data. While these basic statistical methods provide a useful point-of-entry to particle data analysis, more sophisticated statistical and modeling approaches are needed to extract maximal information from such datasets in the future.
A radioanalytical method was developed for the determination of trace plutonium and neptunium in samples composed primarily of uranium. The procedure uses a neodymium oxalate co-precipitation and a ...two-column separation using ion exchange resin to achieve high uranium decontamination, high plutonium and neptunium separation factors and low impurity levels. The separation of the three actinides from each other relies on their oxidation–reduction chemistry. Various measurement techniques can be applied to determine plutonium and neptunium in the purified fractions: i.e., alpha spectrometry, and thermal ionization mass spectrometry. The method development, validation, and applications are discussed.
Bioassay monitoring is an important capability for any facility that works with significant amounts of radioactive material. The speed at which these analyses can be made is critical in the event of ...a potential exposure. In this study, we present a new method that facilitates the rapid separation of uranium from a urine matrix for assay and isotopic determination by inductively coupled plasma mass spectrometry. This method is validated with archived urine samples that were previously analyzed using established, more time consuming methods. The sources of uncertainty for uranium assay and isotopic measurements are modelled using the Monte Carlo method to better understand the precision and accuracy of this method at the limit of quantification.
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