Sr Source Research Articles

CMOS MAPS in a Homogeneous 3D Process for Charged Particle Tracking

This work presents the characterization of deep n-well (DNW) CMOS monolithic active pixel sensors (MAPS) fabricated in a 130 nm homogeneous, vertically integrated technology. An evaluation of the 3D MAPS device performance, designed for application of the experiments at the future high luminosity colliders, is provided through the characterization of the prototypes, including tests with infrared (IR) laser, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">55</sup> Fe and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">90</sup> Sr sources. The radiation hardness study of the technology will also be presented together with its impact on 3D DNW MAPS performance.

Cellular dosimetry of strontium-90 using the Monte Carlo code MCNPX, detection and X-ray microanalysis

The aim of this study is to provide data that increase knowledge about the possible health effects of exposure to 90 Sr contaminant in drinking water. 90 Sr detection in the mouse bone model plays an important complementary role with computational dosimetry in these investigations. S-value (absorbed dose per unit cumulated activity) calculations using Monte Carlo (MC) simulations, 90 Sr detection by liquid scintillation β counting in the femur bone and X-ray microanalysis were carried out. The present work is focused on using MCNPX and its validation at a cellular level. The cytoplasm (Cy), nucleus (N) and 90 Sr radiation source were simulated with the MC code MCNPX. Cells are assumed to be spherical, with the radii of the cell and cell nucleus ranging from 2 to 10 μm. The S-value (in Gy/Bq.s) calculations were provided for a 90 Sr source distributed uniformly in the cell nucleus or cytoplasm and for two source- target combinations (t←s). A comparison between the calculated MC results and the MIRD values agreed very well since the relative deviations are less than 4%. The earliest results of X-ray microanalysis indicated that the 90 Sr was below the detection limit (<0.1%) in the bone tissue. However, the measurements by liquid scintillation showed the presence of 90 Sr in the femur bone.

Mapping and defining sources of variability in bioavailable strontium isotope ratios in the Eastern Mediterranean

The relative contributions of bedrock and atmospheric sources to bioavailable strontium (Sr) pools in local soils was studied in Northern Israel and the Golan regions through intensive systematic sampling of modern plants and invertebrates, to produce a map of modern bioavailable strontium isotope ratios (87Sr/86Sr) for regional reconstructions of human and animal mobility patterns. The study investigates sources of variability in bioavailable 87Sr/86Sr ratios, in particular the intra-and inter-site range of variation in plant 87Sr/86Sr ratios, the range of 87Sr/86Sr ratios of plants growing on marine sedimentary versus volcanic geologies, the differences between ligneous and non-ligneous plants with varying growth and water utilization strategies, and the relative contribution of atmospheric Sr sources from different soil and vegetation types and climatic zones. Results indicate predictable variation in 87Sr/86Sr ratios. Inter- and intra-site differences in bioavailable 87Sr/86Sr ratios average of 0.00025, while the range of 87Sr/86Sr ratios measured regionally in plants and invertebrates is 0.7090 in Pleistocene calcareous sandstone and 0.7074 in mid-Pleistocene volcanic pyroclast. The 87Sr/86Sr ratios measured in plants growing on volcanic bedrock show time dependent increases in atmospheric deposition relative to bedrock weathering. The 87Sr/86Sr ratios measured in plants growing on renzina soils depends on precipitation. The spacing between bedrock 87Sr/86Sr ratios and plants is highest in wet conditions and decreases in dry conditions. The 87Sr/86Sr ratios measured in plants growing on terra rossa soils is relatively constant (0.7085) regardless of precipitation. Ligneous plants are typically closer to bedrock 87Sr/86Sr ratios than non-ligneous plants. Since the bioavailable 87Sr/86Sr ratios currently measured in the region reflect a mix of both exogenous and endogenous sources, changes in the relative contribution of exogenous sources can cause variation over time. Precipitation, the age of the bedrock and the overall Sr concentration must to be taken into consideration when interpreting geographical variation in strontium isotopes throughout a region. Because these factors can change through time, we recommend that Sr data from time periods older than the Holocene be interpreted with caution.

Quantitative analysis of heavy elements and semi‐quantitative evaluation of heavy mineral compositions of sediments in Japan for construction of a forensic soil database using synchrotron radiation X‐ray analyses

We have started to construct a nationwide forensic soil sediment database for Japan, based on the heavy mineral and trace heavy element compositions of stream sediments collected at 3024 points across Japan. The data were measured by high‐resolution synchrotron radiation X‐ray powder diffraction (SR‐XRD) and high‐energy SR X‐ray fluorescence analysis (XRF) using the SR source of SPring‐8, the SR radiation facility in Japan. The automated sampling systems allow the measurement of 130 powder diffraction patterns and 100 XRF spectra per day using sediment samples of just a few milligrams, which enabled us to construct a database of a large number of samples. The concentrations of heavy elements such as rare earth elements, Cs and W up to 500 ppm level in soil sediments can be determined by the calibration curve method by using high‐energy SR‐XRF utilizing monochromatic X‐rays of 116 keV. A heavy element concentration map superimposed on a geographical map of Japan was successfully prepared from these analytical data. The heavy mineral compositions were quantitatively evaluated by using the peak intensity of characteristic XRD peaks of the component minerals measured by a Debye–Scherrer camera having a radius of 286.5 mm, recorded with an imaging plate and monochromatic X‐rays (λ = 1.0 Å). This study demonstrates that XRF and XRD data collected from the sediments of Shizuoka Prefecture closely reflect the geological and geographical signature of the sediment samples, which can be used for the provenance determination of soil evidence from a crime scene. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Sources of Sr and S In Aluminum-Phosphate-Sulfate Minerals In Early-Middle Triassic Sandstones (Iberian Ranges, Spain) and Paleoenvironmental Implications for the West Tethys

Aluminum-phosphate–sulfate (APS) minerals, formed during early diagenesis in relation to acid meteoric waters, are the main host of Sr and S in the Early–Middle Triassic continental sandstones of the Iberian Ranges (east of the Iberian Peninsula). The sources of these elements and the effects of paleoenvironmetal changes on these sources and on the formation of APS minerals during Early–Middle Triassic times, were established on the basis of Sr and S isotopic analyses. The S and Sr data (d34S V-CDT = +11 to +14% and 87Sr/86Sr = 0.7099–0.7247, respectively) can be interpreted as resulting from mixing of different sources. Strontium was sourced from the dissolution of pre-existing minerals like K-feldspar and clay minerals inherited from the source areas, causing high radiogenic values. However, the isotopic signal must also be influenced by other sources, such as marine or volcanic aerosol that decreased the total 87Sr/86Sr ratios. Marine and volcanic aerosols were also sources of sulfur, but the d34S was lowered by dissolution of pre-existing sulfides, mainly pyrite. Pyrite dissolution and volcanic aerosols would also trigger the acid conditions required for the precipitation of APS minerals. APS minerals in the study area are found mainly in the Canizar Formation (Olenekian?–Aegian), which has the lowest 87Sr/86Sr ratios. The lower abundance of APS minerals in the Eslida Formation (Aegian–Pelsonian) may indicate change in the acidity of pore water towards more alkaline conditions, while the increased 87Sr/86Sr ratios imply decreased Sr input from volcanic activity and/or marine aerosol inputs during Anisian times. Therefore, the decrease in abundance of APS minerals from the Early to Middle Triassic and the variations in the sources of Sr and S are indicative of changes in paleoenvironmental conditions during the beginning of the Triassic Period. These changes from acid to more alkaline conditions are also coincident with the first appearance of carbonate paleosols, trace fossils, and plant fossils in the upper part of the Canizar Formation (and more in the overlying Eslida Formation) and mark the beginning of biotic recovery in this area. The presence of APS minerals in other European basins of the Western Tethys (such as the German Basin, the Paris Basin and the southeastern France and Sardinia basins) could thus also indicate that unfavorable environmental conditions caused delay in biotic recovery in those areas. In general, the presence of APS minerals may be used as an indicator of arid, acidic conditions unfavorable to biotic colonization.

Dissolved strontium in the subterranean estuary – Implications for the marine strontium isotope budget

Submarine groundwater discharge (SGD) to the ocean supplies Sr with less radiogenic 87Sr/86Sr than seawater, and thus constitutes an important term in the Sr isotope budget of the modern ocean. However, few data exist for Sr in coastal groundwater or in the geochemically dynamic subterranean estuary (STE). We examined Sr concentrations and isotope ratios from nine globally-distributed coastal sites and characterized the behavior of Sr in the STE. Dissolved Sr generally mixed conservatively in the STE, although large differences were observed in the meteoric groundwater end-member Sr concentrations among sites (0.1–24μM Sr). Strontium isotope exchange was observed in the STE at five of the sites studied, and invariably favored the meteoric groundwater end-member signature. Most of the observed isotope exchange occurred in the salinity range 5–15, and reached up to 40% exchange at salinity 10. Differences in fresh groundwater Sr concentrations and isotope ratios (87Sr/86Sr=0.707–0.710) reflected aquifer lithology. The SGD end-member 87Sr/86Sr must be lower than modern seawater (i.e., less than 0.70916) in part because groundwater Sr concentrations are orders of magnitude higher in less-radiogenic carbonate and volcanic island aquifers. A simple lithological model and groundwater Sr data compiled from the literature were used to estimate a global average groundwater end-member of 2.9μM Sr with 87Sr/86Sr=0.7089. This represents a meteoric-SGD-driven Sr input to the ocean of 0.7–2.8×1010molSry−1. Meteoric SGD therefore accounts for 2–8% of the oceanic Sr isotope budget, comparable to other known source terms, but is insufficient to balance the remainder of the budget. Using reported estimates for brackish SGD, the estimated volume discharge at salinity 10 (7–11×1015Ly−1) was used to evaluate the impact of isotope exchange in the STE on the brackish SGD Sr flux. A moderate estimate of 25% isotope exchange in the STE gives an SGD Sr end-member 87Sr/86Sr of 0.7091. The brackish SGD Sr flux thus accounts for 11–23% of the marine Sr isotope budget, but does not appear sufficient to balance the ∼40% remaining after other known sources are included. Substantial uncertainties remain for estimating the SGD source of Sr to the global ocean, especially in the determination of the volume flux of meteoric SGD, and in the paucity of measurements of groundwater Sr isotope composition in major SGD regions such as Papua New Guinea, the South America west coast, and West Africa. Consequently, our global estimate should be viewed with some caution. Nevertheless, we show that the combined sources of meteoric SGD and brackish SGD coupled with isotope exchange in the STE may constitute a substantial component (∼13–30%) of the modern oceanic 87Sr/86Sr budget, likely exceeding less radiogenic Sr inputs by sedimentary diagenesis and hydrothermal circulation through the mid-ocean ridge system. Temporal variation in SGD Sr fluxes and isotope composition may have contributed to fluctuations in the oceanic 87Sr/86Sr ratio over geologic time.

Operational Status of PF-Ring and PF-AR after the Earthquake

In 2011, two SR sources of KEK, PF-ring and PF-AR, needed to change the operation schedule because of the unprecedented earthquake on March 11. Though the injector linac and the storage rings suffered a serious damage, temporary recovery was accomplished quickly and the trial operation started in May. The regular user operation could be resumed in October 2011. In the restoration work after the earthquake, some old vacuum components were removed from PF-ring. This work fortunately brought an effect of settling the quadrupole-mode longitudinal instability. For the top-up injection of PF-ring, the pulsed sextupole magnet has been used instead of the conventional kicker magnets since 2011. The hybrid-fill mode in place of the single-bunch mode has become available. Recently, the 10-Hz orbit switching for the tandem circularly polarized undulators has been developed for the user operation.

Determination of Sr and Ca sources in small tropical catchments (La Selva, Costa Rica) – A comparison of Sr and Ca isotopes

A comparative study of Sr and Ca isotopes was conducted to assess solute sources and effects of biogeochemical processes on surface water and groundwater in four small tropical catchments located at La Selva Biological Station, Costa Rica. Variable concentrations of dissolved Sr2+ and Ca2+ in the catchments are related to mixing of waters from different origin. Three catchments are influenced by high-solute bedrock groundwater, while another catchment is primarily supplied by local recharge. 87Sr/86Sr ratios were employed to discriminate contributions from mineral weathering and atmospheric sources. Solutes in bedrock groundwater have a predominant geogenic origin, whereas local recharge is characterized by low-solute inputs from rainwater and minor in situ weathering releases from nutrient-depleted soils. Bedrock groundwater contributes more than 60% of dissolved Sr2+ to surface discharge in the Salto, Saltito, and Arboleda catchments, whereas the Taconazo catchment receives more than 95% of dissolved Sr2+ from rainwater. δ44/40Ca values of dissolved Ca2+ vary greatly in the catchments, mainly as a result of heterogeneous Ca isotope compositions of the contributing sources. Based on differences in δ44/40Ca values, two distinct bedrock groundwaters discharging at the Salto and the Arboleda catchments are suggested. Effects of biological processes in the plant-soil system on solute generation in the catchments are indicated by variable Ca/Sr ratios. However, these effects cannot clearly be assessed by Ca isotopes due to the strong heterogeneity of δ44/40Ca values of Ca2+ sources and high Ca2+ concentrations in bedrock groundwater.

Identifying origins of and pathways for spring waters in a semiarid basin using He, Sr, and C isotopes: Cuatrocienegas Basin, Mexico

He, C, and Sr isotopes are used to infer spring sources in a water-stressed area. Spring-water origins and pathways in the Cuatrocienegas Basin are revealed by linking structure and geochemistry via regionally extensive fault networks. This study presents the first dissolved noble gas and He isotopic data from northeastern Mexico. Basement-involved faults with complex reactivation histories are important in northeastern Mexico tectonics and affect hydrogeologic systems. The importance of faults as conduits for northeastern Mexico volcanism is recognized, but connections between faulting and the hydrogeologic system have not been extensively investigated. This research tests the hypothesis that Cuatrocienegas Basin springs are divided into two general classes based upon discharge properties: (1) regional carbonate aquifer discharge (mesogenic) mixed with contributions from deeply sourced (endogenic) fluids containing 3 He and CO 2 from the mantle that ascend along basement-involved faults; and (2) carbonate aquifer discharge mixed with locally recharged (epigenic) mountain precipitation. Carbonate and/or evaporite dissolution is indicated by Ca-SO 4 hydrochemical facies. He isotopes range from 0.89 to 1.85 R A (R A is the 3 He/ 4 He of air, 1.4 × 10 −6 ) and have minimal 3 H, from which it is inferred that basement-involved faults permit degassing of mantle-derived He (to 23% of the total He) and CO 2 ( p CO 2 ≤ 10 >−1 atm). Mantle degassing is compatible with the thinned North American lithosphere, as shown in tomographic images. Sr isotopes in both Cuatrocienegas Basin springs and spring-deposited travertine ( 87 Sr/ 86 Sr = 0.707428–0.707468) indicate that carbonate rocks of the regional Cupido aquifer ( 87 Sr/ 86 Sr = 0.7072–0.7076) are the main source of Sr. Rock-water interactions with mafic volcanic rocks ( 87 Sr/ 86 Sr = 0.70333–0.70359) are not inferred to be an important process. Groundwater-dissolved inorganic C origins are modeled using major elements and C isotopes. C isotope data show that ∼30% ± 22% of CO 2 in spring water is derived from dissolution of aquifer carbonates (C carb = 30%), 24% ± 16% is from soil gas and other organic sources (C org = 24%), and 46% ± 33% is from deep sources [Cendo (endogenic crust and mantle) = 46%]. This study demonstrates the presence of mantle-derived 3 He and deeply sourced CO 2 that ascend along basement-penetrating faults and mix with Cupido aquifer groundwater before discharging in Cuatrocienegas Basin springs.

Mapping multiple source effects on the strontium isotopic signatures of ecosystems from the circum‐Caribbean region

A method for mapping strontium isotope ratio (87Sr/86Sr) variations in bedrock and water has been recently developed for use in the interpretation of 87Sr/86Sr datasets for provenance studies. The mapping process adopted the simplifying assumption that strontium (Sr) comes exclusively from weathering of the underlying bedrock. The scope of this bedrock‐only mapping method is thus limited to systems where the contributions of other sources of Sr are minimal. In this paper, we build on this 87Sr/86Sr mapping method by developing a mixing model of Sr fluxes from multiple sources to the bioavailable Sr pool. The new multiple source model includes: (1) quantitative calculations of Sr fluxes from bedrock weathering using an empirical rock weathering model; and (2) addition of sub‐models calculating the contribution of Sr fluxes from atmospheric aerosols based on outputs from global climate model simulations. We compared the performance of the new multiple source model and the bedrock‐only mapping method in predicting observed values from two datasets of bioavailable 87Sr/86Sr from the circum‐Caribbean region (Antilles and Mesoamerica). Although the bedrock‐only method performs relatively well in Mesoamerica (n = 99, MAE = 0.00011, RMSE = 0.00073), its prediction accuracy is lower for the Antillean dataset (n = 287, MAE = 0.0021, RMSE = 0.0027). In comparison, the new multiple source model, which accounts for the deposition of sea salt and mineral dust aerosols, performs comparably well in predicting the observed 87Sr/86Sr values in both datasets (MAE = 0.00040, RMSE = 0.00087 and MAE = 0.00014, RMSE = 0.0010). This study underscores the potential of using process‐oriented spatial modeling to improve the predictive power of Sr isoscapes over large spatial scales and to refine sampling strategies and bioavailable Sr dataset interpretations for provenance studies.

Chemical composition of modern and fossil hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation – Part 2: Alkaline earth elements as tracers of watershed hydrochemistry and provenance

Abstract. This study demonstrates that alkaline earth elements in enamel of hippopotamids, in particular Ba and Sr, are tracers for water provenance and hydrochemistry in terrestrial settings. The studied specimens are permanent premolar and molar teeth found in modern and fossil lacustrine sediments of the Western Branch of the East African Rift system (Lake Kikorongo, Lake Albert, and Lake Malawi) and from modern fluvial environments of the Nile River. Concentrations in enamel vary by two orders of magnitude for Ba (120–9336 μg g−1) as well as for Sr (9–2150 μg g−1). The variations are partially induced during post-mortem alteration and during amelogenesis, but the major contribution originates ultimately from the variable water chemistry in the habitats of the hippopotamids which is controlled by the lithologies and weathering processes in the watershed areas. Amelogenesis causes a distinct distribution of MgO, Ba and Sr in modern and fossil enamel, in that element concentrations increase along profiles from the outer rim towards the enamel–dentin junction by a factor of 1.3–1.9. These elements are well correlated in single specimens, thus suggesting that their distribution is determined by a common, single process, which can be described by closed system Rayleigh crystallization of bioapatite in vivo. Enamel from most hippopotamid specimens has Sr/Ca and Ba/Ca which are typical for herbivores. However, Ba/Sr ranges from 0.1 to 3 and varies on spatial and temporal scales. Thus, Sr concentrations and Ba/Sr in enamel differentiate between habitats having basaltic mantle rocks or Archean crustal rocks as the ultimate sources of Sr and Ba. This provenance signal is modulated by climate change. In Miocene to Pleistocene enamel from the Lake Albert region, Ba/Sr decreases systematically with time from 2 to 0.5. This trend can be correlated with changes in climate from humid to arid, in vegetation from C3 to C4 biomass as well as with increasing evaporation of the lake water. The most plausible explanation is that Ba mobility decreased with increasing aridification due to preferential deposition with clay and Fe-oxide-hydroxide or barite on the watershed of Lake Albert.

Pre-4.0 billion year weathering on Mars constrained by Rb–Sr geochronology on meteorite ALH84001

The timing and nature of aqueous alteration of meteorite ALH84001 has important implications for the history of water on early Mars, the evolution of the Martian atmosphere, and the potential for early Mars habitability. Rubidium–Sr isotope analyses of mineral separates from igneous-textured and carbonate-rich aliquots of Martian meteorite ALH84001 constrain the age of alteration and the source of fluids. The carbonate-rich aliquot defines a precise Rb–Sr isochron between maskelynite, orthopyroxene, and chromite of 3952±22Ma, and this is interpreted to represent a shock resetting event that was broadly coeval with carbonate precipitation. Carbonate, bulk rock, and multi-mineral separates all have high 87Sr/86Sr ratios that can only have been produced by alteration via a fluid derived through interaction with high Rb/Sr phyllosilicates that were produced prior to 3950Ma. These data confirm that the source of Sr in the fluids was previously altered crustal rock, consistent with fluids that underwent low-temperature water–rock interaction (Eiler et al., 2002; Halvey et al., 2011). These results therefore provide evidence for wet, clay-rich conditions on the surface of Mars prior to ∼4.2Ga.

Implications of carbonate-like geochemical signatures in a sandstone aquifer: Radium and strontium isotopes in the Cambrian Jordan aquifer (Minnesota, USA)

Water–rock interaction in sandstone aquifers can potentially mobilize U-and Th-series radionuclides, resulting in elevated levels of radioactive constituents such as radium (Ra) in groundwater. Previous studies have delineated the sources of Ra in groundwater by assuming that 228Ra/226Ra of groundwater parallels the 232Th/238U activity ratio of aquifer solids. We present an integrated geochemical and isotopic study of groundwater and aquifer solids for major and trace elements, radium (224Ra, 226Ra, 228Ra), strontium isotopes (87Sr/86Sr), and tritium in the Cambrian Jordan quartz sandstone aquifer of southeastern Minnesota (USA). The Jordan aquifer, part of the Cambrian–Ordovician aquifer system of the upper midwestern USA, is characterized by a wide range of Ra activities in groundwater. Uniform Ca–Mg–HCO3− major element composition and patterns in 87Sr/86Sr indicate that interaction with carbonate minerals controls water chemistry. At least one contributing Sr source is radiogenic, yielding 87Sr/86Sr ratios up to 0.71347. Radium-226 activities exhibit especially large variations (<1–418mBqL−1), and the highest radium activities occupy a 100-km-long north–south region. Consistent with the carbonate-like elemental and Sr isotope signatures, 226Ra activity (median 85mBqL−1) is higher than 228Ra (median 47mBqL−1), yielding low 228Ra/226Ra ratios (median 0.5) that would be expected from a lithology preferentially containing U relative to Th, such as carbonate rocks. Collectively, results indicate the primary source of radium to the aquifer is alpha recoil from aquifer solids rather than external inputs of high-Ra waters, indicated by (1) similar 228Ra/226Ra ratios in aquifer solids and groundwater, including low, carbonate-like values in the high-226Ra samples; (2) some association between whole-rock 226Ra levels and groundwater 226Ra activities; and (3) groundwater 224Ra/228Ra averaging near unity. Furthermore, hydrogeologic setting (e.g. presence or absence of overlying carbonate units) is inconsistent with systematic inputs of high-Ra waters from overlying carbonate aquifers. The most proximate source of carbonate material in the sandstone aquifer seems to be the calcite and dolomite cement that yields different geochemical and isotopic fingerprints than silicate minerals would impart. Whole-rock 226Ra/238U≈1 implies that any U enrichment in the carbonate cement occurred at least 350,000years ago. High groundwater Ra activities relative to solids are attributable to anoxic conditions that play a role in maintaining inefficient radium removal for a fresh groundwater system, indicated by the estimated dimensionless whole-rock Ra distribution coefficient of 150–920 (median 560). Coprecipitation of Ra into barite is a potential but unquantified Ra removal mechanism. Overall, radium in the Jordan aquifer provides an example of a naturally-occurring trace element of health significance that may be derived not mainly from the quartz sandstone matrix, but from carbonate material such as calcite and dolomite cement. Especially when combined with complementary tracers such as 87Sr/86Sr, this study demonstrates the usefulness of the 228Ra/226Ra ratio as an indicator of the key mineral phases (silicate vs. carbonate) involved in supplying radium to groundwater.

Riverine particulate material dissolution as a significant flux of strontium to the oceans

The ratio of strontium isotopes, 87Sr/86Sr, in seawater is homogenous at any given time, yet varies considerably throughout the geological record. This variation is thought to stem from changes in the balance of predominantly radiogenic Sr entering the oceans via dissolved riverine transport, and unradiogenic Sr sourced from mid-ocean ridge hydrothermal activity. Recent evidence suggests, however, that hydrothermal exchange at mid-ocean ridges is a factor of 3 too low to balance Sr added to the oceans from dissolved continental riverine fluxes. Here we present evidence that the arrival and subsequent dissolution of riverine particulate material in seawater is a significant contributor of both radiogenic and unradiogenic Sr to the oceans. Batch experiments demonstrate that between 0.15% and 27.36% of Sr is liberated from riverine particulates to seawater within 6 months. The rates of release are dependent on surface area and particulate composition, with volcanic riverine material more reactive than continental riverine particulates. The observed rapid Sr release rate from riverine particulate material has important consequences for both chemical and isotopic mass balances in the ocean and the application of the 87Sr/86Sr weathering proxy to the geological record. The dissolution of riverine particulate material is likely, based on these findings, to at least partially account for the imbalance between Sr sources to the oceans.

The sources of volatile and fluid‐mobile elements in the Sunda arc: A melt inclusion study from Kawah Ijen and Tambora volcanoes, Indonesia

Subduction zone recycling of volatiles (H2O, Cl, S, F) is controlled by the nature of subducted materials and the temperature‐pressure profile of the downgoing slab. We investigate the variability in volatile and fluid‐mobile trace element enrichment in the Sunda arc using melt inclusion data from Kawah Ijen and Tambora volcanoes, together with published data from Galunggung, Indonesia. Combining our results with data from other arcs, we investigate the mobility of these elements during slab dehydration and melting. We observe correlations between Sr, H2O and Cl contents, indicating coupling of these elements during subduction zone recycling. Sulfur is more variable, and fluorine contents generally remain at background mantle values, suggesting decoupling of these elements from H2O and Cl. Partial melting and dehydration models constrain the source of Sr and the volatiles and suggest that the altered oceanic crust (AOC) is the main source of the hydrous component that fluxes into the mantle wedge, in agreement with thermo‐mechanical models. Sediment melt remains an important component for other elements such as Ba, Pb, Th and the LREE. The Indonesian volcanoes have variable concentrations of volatile and fluid‐mobile elements, with Kawah Ijen recording higher AOC‐derived fluid fluxes (Sr/Nd and H2O/Nd) compared to Galunggung and Tambora. Kawah Ijen has H2O/Ce ratios that are comparable to some of the most volatile‐rich magmas from other cold slab subduction zones worldwide, and the highest yet measured in the Sunda arc.

A basement-interacted fluid in the N81 deposit, Pine Point Pb-Zn District, Canada: Sr isotopic analyses of single dolomite crystals

The Mississippi Valley-type Pb-Zn deposits of the Pine Point district (Northwest Territories, Canada) are located close to the eastern edge of the present day Western Canadian Sedimentary Basin. The deposits are thought to have formed as the result of basin-wide fluid flow in the Presqu’ile Barrier, the host to the ore deposits. A laser ablation multi-collector inductively coupled plasma mass spectrometric study of 87Sr/86Sr ratios of ore-related dolomites from the N81 deposit at Pine Point indicates that at least two sources of Sr were present in the mineralizing system. One fluid has a range in Sr isotopic values from 0.07073 to 0.71200 and is interpreted to be derived from Middle Devonian seawater that interacted with clastic units in the basin. The second fluid has higher Sr isotopic values (up to 0.71520), similar to those found in some Canadian Shield brines, and is interpreted to represent an evaporated seawater-derived brine which has interacted with crystalline basement rocks. Reactivation of old structures in the basement may have provided a pathway for cross-formation fluid flow to the site of mineralization. The data suggest that the stratigraphic location of the Pine Point District, near the interface between the Western Canadian Sedimentary Basin and its basement, may have exerted a fundamental control on the formation of these deposits.

New knowledge about the bremsstrahlung image of strontium-89 with the scintillation camera

Strontium-89 ((89)Sr) chloride has been used to treat metastases in bone. A method to visualize the distribution of (89)Sr chloride with a scintillation camera was developed in 1996. Studies using bremsstrahlung imaging have shown that (89)Sr accumulates in bone and that the bremsstrahlung generated from biological tissue surrounding bone does not exceed 30 keV. However, it was not clear how low-energy bremsstrahlung from bone can produce peak energy levels of around 75 keV. We speculate that a different (unidentified) factor is involved. The energy spectrum of an (89)Sr source was acquired with a scintillation camera with or without a low-to-medium-energy general-purpose collimator. The energy window was set at 20-650 keV for 4 windows. A 50-mm thick acrylic block was placed between the scintillation camera and the (89)Sr source to exclude the effects of bremsstrahlung. The energy spectrum of (89)Sr covered with lead was acquired using the scintillation camera without a collimator. With the collimator the energy spectrum curve was similar to that without the 50 mm of acrylic. The energy spectrum curve showed peaks at about 75, 170, and 520 keV. Without the collimator the energy spectrum showed a similar curve but no peak at 75 keV peak. The curve was similar to that obtained with the scintillation camera and the collimator; however, the curve obtained when the (89)Sr source had been placed in a lead container was similar to that obtained when the source was unshielded, and the collimator was not attached to the scintillation camera. If bremsstrahlung of (89)Sr produces an image, a low-energy spectrum region should decrease when acrylic is placed between the (89)Sr source and the scintillation camera. However, similar curves were obtained both with the acrylic in place and without the acrylic. Therefore, we believe that the radiation detected by the scintillation camera was not bremsstrahlung due to the beta rays of (89)Sr. Most (89)Sr preparations are contaminated by (85)Sr, and most of the gamma ray energy of (85)Sr is 514 keV. The scintillation camera detected the characteristic X-ray energy of about 75 keV from the materials of the collimator (lead and others) through interaction with the gamma rays of (85)Sr.

Modernization of the vacuum system of synchrotron radiation sources at the National Research Centre Kurchatov Institute

The modernization project of the vacuum system of the synchrotron radiation source at the National Research Centre Kurchatov Institute (NRC KI) has been designed and is being implemented; it includes a change in the system to high-voltage power sources for NMD and PVIG-0.25/630 pumps. The system is controlled via the CAN bus, and the vacuum is controlled by measuring pump currents in a range of 0.0001–10 mA. The system ensures a vacuum of 10−7 Pa. The status is mapped and the data collected into the archive are processed on the MS SQL Server platform. The efficiency and reliability of the vacuum system is increased by this work, making it possible to improve the main parameters of the SR source.

Cation stoichiometry optimization of SrTiO3 (110) thin films with atomic precision in homogeneous molecular beam epitaxy

We study the evolution of surface reconstructions on SrTiO3 (110) determined by cation concentration ratio and find it detectable by high energy electron diffraction (RHEED) even at high temperature up to 800 °C. The evaporation rate of Sr and Ti sources can be calibrated precisely by monitoring RHEED patterns in situ and in real time during the extended homogeneous oxide molecule beam epitaxy growth of SrTiO3 (110) film. High quality film is obtained with deviation of cation stoichiometry less than 0.5%.

Determination of foliar Ca/Sr discrimination factors for six tree species and implications for Ca sources in northern hardwood forests

Discrimination during foliar uptake between the alkaline earth elements Ca and Sr must be understood to fully utilize Ca/Sr and 87Sr/86Sr ratios as a monitor of Ca sources to trees. The aim of this study was to determine Ca/Sr discrimination factors [DF = (Ca/Srplant tissue)/ (Ca/Srnutrient source)] for six tree species in a northern hardwood forest and use foliar chemistry to consider whether species access measurably different soil reservoirs of Ca and Sr. This was accomplished by measuring the Ca/Sr and 87Sr/86Sr ratios of foliage from individual tree species in mixed stands and comparing these ratios to those of soil extracts from soil pits co-located at six sites in the White Mountains, New Hampshire (USA). For three species for which DFs have been previously determined, the source of Ca and Sr in foliage can be traced predominantly to recycling of material from organic horizons. Foliar and soil chemistry is consistent with each of the tree species in these six sites deriving Ca and Sr predominantly from the Oie horizon. Thus we can estimate DFs (±1sd) for sugar maple (Acer saccharum Marsh.; 1.16 ± 0.13), yellow birch (Betula alleghaniensis Britt.; 1.31 ± 0.10), white birch (Betula papyrifera Marsh.; 1.30 ± 0.14), pin cherry (Prunus pensylvanica L.f.; 1.24 ± 0.09), American beech (Fagus grandifolia Ehrh.; 1.78 ± 0.17) and red maple (Acer rubrum L.; 1.90 ± 0.15). These estimates of discrimination factors allow refinement in the use of Ca/Sr and 87Sr/86Sr ratios of foliage to trace Ca sources to plants.