Vesicle Size Distribution as a Novel Nuclear Forensics Tool.

The first nuclear bomb detonation on Earth involved a plutonium implosion-type device exploded at the Trinity test site (33°40'38.28″N, 106°28'31.44″W), White Sands Proving Grounds, near Alamogordo, New Mexico. Melting and subsequent quenching of the local arkosic sand produced glassy material, designated "Trinitite". In cross section, Trinitite comprises a thin (1-2 mm), primarily glassy surface above a lower zone (1-2 cm) of mixed melt and mineral fragments from the precursor sand. Multiple hypotheses have been put forward to explain these well-documented but heterogeneous textures. This study reports the first quantitative textural analysis of vesicles in Trinitite to constrain their physical and thermal history. Vesicle morphology and size distributions confirm the upper, glassy surface records a distinct processing history from the lower region, that is useful in determining the original sample surface orientation. Specifically, the glassy layer has lower vesicle density, with larger sizes and more rounded population in cross-section. This vertical stratigraphy is attributed to a two-stage evolution of Trinitite glass from quench cooling of the upper layer followed by prolonged heating of the subsurface. Defining the physical regime of post-melting processes constrains the potential for surface mixing and vesicle formation in a post-detonation environment.

Comparative Investigation between In Situ Laser Ablation Versus Bulk Sample (Solution Mode) Inductively Coupled Plasma Mass Spectrometry (ICP-MS) Analysis of Trinitite Post-Detonation Materials.

In the event of the interception of illicit nuclear materials or detonation of a nuclear device, timely and accurate deciphering of the chemical and isotopic composition of pertinent samples is pivotal in enhancing both nuclear security and source attribution. This study reports the results from a first time (to our knowledge), detailed comparative investigation conducted of Trinitite post-detonation materials using both solution mode (SM) and laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS) techniques. Trace element abundances determined for bulk Trinitite samples subsequent to digestion and preparation for SM-ICP-MS analysis compare favorably to calculated median concentrations based on LA-ICP-MS analyses for the identical samples. The trace element concentrations obtained by individual LA-ICP-MS analyses indicate a large scatter compared to the corresponding bulk sample SM-ICP-MS results for the same sample; this feature can be attributed to the incorporation into the blast melt of specific, precursor accessory minerals (minerals in small quantities, such as carbonates, sulfates, chlorites, clay, and mafic minerals) present at ground zero. The favorable comparison reported here validates and confirms the use of the LA-ICP-MS technique in obtaining accurate forensic information at high spatial resolution in nuclear materials for source attribution purposes. This investigation also reports device-like (240)Pu/(239)Pu ratios (∼0.022) for Pu-rich regions of the blast melt that are also characterized by higher Ca and U contents, which is consistent with results from previous studies.

Sourcing of Copper and Lead within Red Inclusions from Trinitite Postdetonation Material.

Historical postdetonation materials resulting from nuclear testing can be used to develop methodologies for source attribution, in particular if the chemical and isotopic signatures of the device are public domain. The samples analyzed in this study are from the world's first nuclear bomb explosion in 1945, the Trinity Test, and produced the postdetonation material "Trinitite". The latter is a glassy material that resulted from the melting of the natural sand present at ground zero (Alamogordo, NM) and incorporated components of the device. Chemical and isotopic (e.g., Pu) information on the device is declassified and, therefore, methodologies for fingerprinting fuel and other device components can be verified. One type of Trinitite contains red inclusions that are characterized by high concentrations of Pb (between 438 and 26,631 µg/g) and Cu (between 404 and 22,280 µg/g) that are in general positively correlated. Pb isotope compositions for the red inclusion areas exhibit a large variation and indicate mixing between Pb from at least 3 different sources: 1- natural geological background (arkosic sand) present at ground zero; 2- anthropogenic component from the device; and 3- industrial Cu used for wiring in the device. Based on the Pb isotope ratios for the red inclusions within Trinitite, it is likely that the anthropogenic Pb derives from Buchans Mine (Newfoundland, Canada), which is in agreement with a previous investigation. Products of industrial Cu manufacturing (e.g., pennies) were analyzed for their trace element abundances and Pb isotope compositions; these suggest that Cu employed within the device's wiring was derived from two Cu ore deposits within the USA.

Oxygen isotope composition of trinitite postdetonation materials.

Trinitite is the melt glass produced subsequent the first nuclear bomb test conducted on July 16, 1945, at White Sands Range (Alamagordo, NM). The geological background of the latter consists of arkosic sand that was fused with radioactive debris and anthropogenic materials at ground zero subsequent detonation of the device. Postdetonation materials from historic nuclear weapon test sites provide ideal samples for development of novel forensic methods for attribution and studying the chemical/isotopic effects of the explosion on the natural geological environment. In particular, the latter effects can be evaluated relative to their spatial distribution from ground zero. We report here δ(18)O(‰) values for nonmelted, precursor minerals phases (quartz, feldspar, calcite), "feldspathic-rich" glass, "average" melt glass, and bulk (natural) unmelted sand from the Trinity site. Prior to oxygen isotope analysis, grains/crystals were examined using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to determine their corresponding major element composition. δ(18)O values for bulk trinitite samples exhibit a large range (11.2-15.5‰) and do not correlate with activity levels for activation product (152)Eu; the latter levels are a function of their spatial distribution relative to ground zero. Therefore, the slow neutron flux associated with the nuclear explosion did not perturb the (18)O/(16)O isotope systematics. The oxygen isotope values do correlate with the abundances of major elements derived from precursor minerals present within the arkosic sand. Hence, the O isotope ratios documented here for trinitite melt glass can be attributed to a mixture of the respective signatures for precursor minerals at the Trinity site prior to the nuclear explosion.

Evidence for the alkaline nature of parental carbonatite melts at Oka complex in Canada.

The Earth's sole active carbonatite volcano, Oldoinyo Lengai (Tanzania), is presently erupting unique natrocarbonatite lavas that are characterized by Na- and K-bearing magmatic carbonates of nyerereite [Na2Ca(CO3)2] and gregoryite [(Na2,K2,Ca)CO3]. Contrarily, the vast majority of older, plutonic carbonatite occurrences worldwide are dominated by Ca-(calcite) or Mg-(dolomite)-rich magmatic carbonates. Consequently, this leads to the conundrum as to the composition of primary, mantle-derived carbonatite liquids. Here we report a detailed chemical investigation of melt inclusions associated with intrusive (plutonic) calcite-rich carbonatites from the ~120 Ma carbonatite complex of Oka (Canada). Melt inclusions are hosted by magnetite (Fe3O4), which crystallizes through a significant period of carbonatite melt solidification. Our results indicate mineral assemblages within the melt inclusions that are consistent with those documented in natrocarbonatite lavas. We propose therefore that derivation of alkali-enriched parental carbonatite melts has been more prevalent than that preserved in the geological record.

Lead isotopic composition of trinitite melt glass: evidence for the presence of Canadian industrial lead in the first atomic weapon test.

The Pb isotopic compositions for 51 spots of melt glass in 11 samples of trinitite have been determined by laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). Trinitite glass yields a large range of Pb isotopic compositions (i.e., (206)Pb/(204)Pb = 17.08-19.04), which reflect mixing between industrial Pb from materials used in the Trinity test and natural geologic components. Areas within trinitite melt glass containing high concentrations of both Cu and Pb, which are derived from the bomb and blast site-related components, were used for delineating the Pb isotopic composition corresponding to the anthropogenic Pb component. Comparison between the isotopic composition estimated here for the industrial Pb used in the Trinity test and those from known Pb deposits worldwide indicates close agreement with ore from the Buchans mine (Newfoundland, Canada). The Buchans mine was active during the time of the Trinity test and was operated by the American Smelting and Refining Company, which could have provided the Pb used in the test. The industrial Pb used in the Trinity test materials is not documented in the literature (or declassified) but could have been present in bricks, solder, pigs, or some other anthropogenic component related to the experiment.

Isotopic fingerprinting of the world's first nuclear device using post-detonation materials.

In the event of a rogue nuclear attack or interception of illicit nuclear materials, timely forensic investigations are critical for accurate source attribution. Uranium (U) and plutonium (Pu) isotopic ratios of intercepted materials or postdetonation samples are, perhaps, the most valuable evidence in modern nuclear forensics. These ratios simultaneously provide information regarding the material's ''age'' (i.e., time elapsed since last purification), actinide concentrations, and relevant isotopic ratios/enrichment values. Consequently, these isotope signatures are invaluable in determining the origin, processing history, and intended purpose of any nuclear material. Here we show, for the first time, that it is feasible to determine the U and Pu isotopic compositions of historic nuclear devices from their postdetonation materials utilizing in situ U isotopic measurements. The U isotopic compositions of trinitite glass, produced subsequent to the world's first atomic explosion, indicate two sources: the device's tamper, composed of natural U that underwent fission during detonation, and natural U from the geological background. Enrichments in (234,235,236)U reflect the in situ decay of (238,239,240)Pu, the fuel used in the device. Time-integrated U isotopic modeling yields "supergrade" compositions, where (240)Pu/(239)Pu ≈ 0.01-0.03 and (238)Pu/(239)Pu ≈ 0.00011-0.00017, which are consistent with the Pu originating from the Hanford reactor. Spatially resolved U isotopic data of postdetonation debris reveal important details of the device in a relatively short time frame (hours). This capacity serves as an important deterrent to future nuclear threats and/or terrorist activities and is critical for source attribution and international security.

Strontium isotope (87Sr/86Sr) variability in the Nile Valley: identifying residential mobility during ancient Egyptian and Nubian sociopolitical changes in the New Kingdom and Napatan periods.

As a successful technique for identifying residential mobility in other areas, this study investigates the feasibility of using 87Sr/86Sr analysis to track the movements of the ancient peoples of Egypt and Nubia in the Nile Valley, who interacted via trade, warfare, and political occupations over millennia. Dental enamel from faunal remains is used to examine variability in strontium sources in seven regional sites; human enamel samples are analyzed from eight Nile Valley sites in order to trace human movements. The faunal samples show a wide range of 87Sr/86Sr values demonstrating that some animals were raised in a variety of locales. The results of the human samples reveal overlap in 87Sr/86Sr values between Egyptian and Nubian sites; however, Egyptian 87Sr/86Sr values (mean/median [0.70777], sd [0.00027]) are statistically higher than the Nubian 87Sr/86Sr values (mean [0.70762], median [0.70757], sd [0.00036], suggesting that it is possible to identify if immigrant Egyptians were present at Nubian sites. Samples examined from the site of Tombos provide important information regarding the sociopolitical activities during the New Kingdom and Napatan periods. Based on a newly established local 87Sr/86Sr range, human values, and bioarchaeological evidence, this study confirms the preliminary idea that immigrants, likely from Egypt, were present during the Egyptian New Kingdom occupation of Nubia. In the subsequent Napatan period when Nubia ruled Egypt as the 25th Dynasty, 87Sr/86Sr values are statistically different from the New Kingdom component and indicate that only locals were present at Tombos during this developmental time.

Incorporation of neptunium(VI) into a uranyl selenite.

The incorporation of neptunium(VI) into the layered uranyl selenite Cs[(UO(2))(HSeO(3))(SeO(3))] has yielded the highest level of neptunium uptake in a uranyl compound to date with an average of 12(±3)% substitution of Np(VI) for U(VI). Furthermore, this is the first case in nearly 2 decades of dedicated incorporation studies in which the oxidation state of neptunium has been determined spectroscopically in a doped uranyl compound and also the first time in which neptunium incorporation has resulted in a structural transformation.

Time-resolved self-assembly of a fullerene-topology core-shell cluster containing 68 uranyl polyhedra.

A complex core-shell cluster consisting of 68 uranyl peroxo polyhedra, 16 nitrate groups, and ~44 K(+) and Na(+) cations was obtained by self-assembly in alkaline aqueous solution under ambient conditions. Crystals formed after a month and were characterized. The cluster, designated as {U(1)⊂U(28)⊂U(40R)}, contains a fullerene-topology cage built from 28 uranyl polyhedra. A ring consisting of 40 uranyl polyhedra linked into five-membered rings and 16 nitrate groups surrounds this cage cluster. Topological pentagons in the cage and ring are aligned, and their corresponding rings of uranyl bipyramids are linked through K(+) cations located between the two shells. A partially occupied U site is located at the center of the cluster. Time-resolved small-angle X-ray scattering and electrospray ionization mass spectrometry demonstrated that the U(28) cage cluster formed in solution within an hour, whereas the U(40R) shell formed around the cage cluster after more than several days.

Interstitial incorporation of plutonium into a low-dimensional potassium borate.

The molten boric acid flux reaction of PuBr(3) with KBO(2) at 200 °C results in the formation of large light-yellow crystals of K[B(5)O(7)(OH)(2)]·H(2)O:Pu(4+). Single-crystal X-ray diffraction experiments on the Pu-doped K[B(5)O(7)(OH)(2)]·H(2)O demonstrate two features: (1) K[B(5)O(7)(OH)(2)]·H(2)O:Pu(4+) adopts a one-dimensional borate chain structure with void spaces between the chains. (2) The doping plutonium atoms do not reside on the potassium sites. The latter are not fully occupied. Both laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and energy-dispersive spectrometry analyses indicate that plutonium atoms are uniformly distributed in crystals of K[B(5)O(7)(OH)(2)]·H(2)O with an atomic K:Pu ratio of approximately 65:1 measured by LA-ICP-MS. UV-vis-NIR spectra taken from both freshly made and one day old crystals show that the plutonium present within the crystals is predominantly characterized by Pu(IV). A small amount of Pu(III) is also present initially, but slowly oxidized to Pu(IV) via interaction with oxygen in the air. X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopic measurements confirm that plutonium is mainly present as a form similar to that of a PuO(2) cluster. The combined results suggest that the clusters containing Pu(IV) ions are uniformly distributed in the void spaces between the borate chains.

Incorporation of neptunium(V) and iodate into a uranyl phosphate: implications for mitigating the release of 237Np and 129I in repositories.

The simultaneous incorporation of IO3(-) and NpO2+ into Ba3(UO2)2(HPO4)2(PO4)2 (BaUP), which serves as a model for uranyl alteration phases, was investigated. LA-ICP-MS data demonstrate that the incorporation of both of these species is significantly enhanced when they are present together. The most probable explanation is that charge balance is obtained by the coupled substitutions of NpO2+ <--> UO2(2+) and IO3(-) <--> HPO4(2-). According to the LA-ICP-MS results, in the absence of iodate as much as 2.91 +/- 0.14 to 3.44 +/- 0.25% of the uranium in BaUP can be replaced by neptunium. When iodate is present in the reaction, the amount of uranium substitution by neptunium increases to 6.05 +/- 0.65% to 7.93 +/- 0.83%. The net increase for neptunium is 116 +/- 0.30% to 225 +/- 0.25%. Similarly, in the absence of NpO2+, iodate incorporation into BaUP reaches an I/U level of 0.0021 +/- 0.0004 to 0.0038 +/- 0.0005; whereas in its presence there is an increase to as much as 100 +/- 0.11% to 0.0042 +/- 0.0008.

Is lead a concern in Canadian autistic children?

BACKGROUND: The Centers for Disease Control and Prevention (CDC) threshold for intervention for blood lead level (BLL) is greater than 0.48 µmol/L, but new research suggests that there are adverse effects at any level of exposure. Children with autism are at increased risk for lead exposure and intoxication, and have later and more prolonged exposures because of exploratory oral behaviours and pica. OBJECTIVE: To estimate the mean BLL and prevalence of high BLL in a convenience sample of autistic children living in northern Alberta, based on the CDC threshold for intervention. METHODS: Children with autism were recruited from the clinics at the Glenrose Rehabilitation Hospital in Edmonton, Alberta. A complete blood count and differential, serum ferritin and BLL were requested after consent was obtained. Summary statistics were reported. For dichotomous outcomes, proportions were presented. Continuous outcomes for the two groups with a BLL of 0.1 µmol/L or greater, or less than 0.1 µmol/L were compared. RESULTS: None of the children tested had a BLL exceeding 0.48 µmol/L. Nine children (19%) had BLLs of 0.1 µmol/L or greater but less than 0.48 µmol/L, and 39 (81%) had BLLs of less than 0.1 µmol/L. Those with a BLL of 0.1 µmol/L or greater had significantly more pica or oral exploratory behaviours. CONCLUSION: Children with autism in northern Alberta may not be at risk for elevated BLLs that exceed the CDC threshold for intervention. They should be screened for lead exposure risk factors and tested if there are risks, especially behaviours relating to pica and oral exploration of objects. Clinicians may need to further explore the reasons for low-level exposures to lead in the autistic population.

Does iodate incorporate into layered uranyl phosphates under hydrothermal conditions?

Three new layered uranyl phosphates, Ba(3)(UO(2))(2)(HPO(4))(2)(PO(4))(2), Ba(UO(2))F(PO(4)), and Cs(2)(UO(2))(2)(PO(4))(2), were synthesized under mild hydrothermal conditions. These compounds serve as models for uranium alteration phases that might form when spent nuclear fuel is subjected to oxidizing groundwater containing dissolved phosphate. In order to address the possibility of the incorporation of the key fission product (129)I in the form of iodate into uranyl alteration phases, the substitution of IO(3)(-) for the structurally related PO(3)(OH)(2-) or PO(4)(3-) unit was probed. Iodate incorporation into these phases was investigated using LA-ICP-MS, and these data indicate incorporation of iodine with levels as high as 4162 ppm.

Temporal trends of pollution Pb and other metals in east-central Baffin Island inferred from lake sediment geochemistry.

Concentrations and stable isotope ratios of lead (Pb) from lake sediments were used to quantify temporal patterns of anthropogenic Pb pollution in the Clyde River region of Baffin Island, Arctic Canada. Surface sediments from eight lakes on eastern Baffin Island and one from northern-most Greenland, spanning a gradient of 20 degrees latitude, showed great variability with respect to Pb concentration and stable isotopic Pb ratios, with little apparent latitudinal trend. To constrain the temporal evolution of regional Pb pollution, a well-dated core from one of the sites, Lake CF8 on east-central Baffin Island, was analyzed geochemically at high stratigraphic resolution. A pronounced decrease in the (206)Pb/(207)Pb ratio occurs in sediments deposited between 1923 and the mid-1970s, likely reflecting alkyl-Pb additives derived from the combustion of fossil fuels at a global scale. A two-component mixing model indicates that 17-26% of the Pb in the labile fraction of sediments deposited in Lake CF8 between 2001 and 2005 is from anthropogenic input. A Pb-Pb co-isotopic plot ((206)Pb/(207)Pb vs.(208)Pb/(206)Pb ratios) of the Lake CF8 time series data indicates multiple possible sources of industrial Pb pollution. Despite widespread reductions in industrial Pb emissions since the 1970s, there is no evidence for attendant reductions of pollution Pb at Lake CF8. Enhanced scavenging from increased primary production as well as changing precipitation rates as climate warms may represent important factors that modulate Pb deposition to Lake CF8, and Arctic lakes elsewhere.

Symmetry versus minimal pentagonal adjacencies in uranium-based polyoxometalate fullerene topologies.

C U soon: Clusters containing 60, 44, and 36 uranyl peroxide hydroxide polyhedra (see picture) adopt fullerene topologies of maximum symmetry. The largest of these, denoted U60, is topologically identical to C(60) with no pentagonal adjacencies and the highest possible symmetry. U44 adopts the topology with maximum symmetry rather than that with the lowest number of pentagonal adjacencies.