Synchrotron Radiation X-ray Fluorescence Analysis Research Articles

Enhancement of mineral density and mechanical properties in root caries treated with silver diammine fluoride and glass ionomer cement, with emphasis on silver ion distribution

ObjectivesThis study aimed to measure the distribution of silver ion (Ag+), mineral recovery, and nanohardness in carious lesions and comprehensively evaluate the degree of dentin restoration. MethodsSixty human teeth with root caries were randomly assigned to the control, silver diammine fluoride (SDF) [Safo], and SDF+Glass ionomer cement (GIC) treatment [Safo+Fuji] groups. Micro-computed tomography (CT) was performed at five time points for each sample before/after treatment to evaluate mineral density within and around carious lesions. Three months following treatment, 12 samples were selected for synchrotron radiation X-ray fluorescence analysis to evaluate Ag+ distribution, while 15 samples were selected for nanoindentation. Data were analyzed using Dunnett's T3 test for micro-CT and Wilcoxon rank sum test with Bonferroni correction (p = 0.017) for nanoindentation. The correlation between hardness and mineral change was analyzed using the Spearman rank correlation coefficient. ResultsThe Safo and Safo+Fuji groups showed significantly higher mineral recovery rates than did the control group (p<0.001). In the Safo group, Ag+ accumulated in the deeper layers rather than the superficial layer of caries. In the Safo+Fuji group, Ag+ was found evenly distributed throughout caries, with only a few Ag+ detected in the GIC layer. Hardness in the Safo+Fuji group was significantly higher compared with the Safo group at depths in the range of 10–50 µm. ConclusionIn the presence of GICs, SDF exhibited high remineralization capacity when diffusing throughout carious lesions over time. Combined treatment with SDF and GIC could strengthen root dentin even in the presence of caries. Clinical significanceWe found that combination treatment with SDF and GIC could increase mineral density in caries and improve the hardness of the tooth structure compared with fluoride-based agents alone. These findings might pave the way for future clinical trials to determine the therapeutic potential of nanotechnology-based restorative materials.

High-energy SR-XRF Imaging of Cesium and Trace Elements in Mouse Kidneys: Short Communication.

For understanding trace element dynamics in tissues, methods for analyzing elemental distribution and localization without destroying tissue structures and cell arrangements are desired. Synchrotron radiation X-ray fluorescence (SR-XRF) analysis is one of the non-destructive and multi-element simultaneous analyses. The kidney is the major excretion pathway of cesium (Cs) taken into the body, and an understanding of cesium distribution in the kidney would be useful for establishing technology to facilitate the excretion of radioactive Cs from the body due to nuclear disasters. In the present study, the distribution of cesium and trace elements, such as iron (Fe) and zinc (Zn), corresponding to the kidney structure was examined in Cs-administered mice by SR-XRF imaging with high-energy excitation X-rays (40keV). By beam scanning with a 200-µm square beam, clear Cs images corresponding to the renal layer structure were obtained for the renal specimen at the early phase after Cs administration with the mean renal Cs concentration of 24.1 ± 3.2μg/g. Cs was distributed mainly in the medulla and the outer stripe of the outer medulla located in the center area of the kidney. Unlike the Cs distribution, endogenous Fe and Zn tended to be lower in the medulla than in the outer stripe of the outer medulla and the cortex. This method is effective for analyzing Cs distribution because it can simultaneously analyze the distribution of endogenous trace elements.

Fluid mineralization of the Dongtongyu gold deposit in the southern margin of North China craton: Evidence from microthermometry and composition of fluid inclusions

In this study, petrographic, microthermometric, and synchrotron radiation X-ray fluorescence (SRXRF) analyses of fluid inclusions were conducted to shed light on the mineralization mechanism of the Dongtongyu deposit and provide some evidence of the relationship among CO2, Au, and other ore elements (e.g., Cu, Fe, Zn, and Pb) in ore-forming fluids. The ore-forming fluid is characterized as the H2O–CO2–NaCl system with medium–high temperatures and low salinities. Four structural mineralization stages are distinguished: Pyrite-quartz (Stage 1), gold-quartz-pyrite (Stage 2), gold-quartz-polymetallic sulfide (Stage 3), and quartz-calcite (Stage 4). Fluid inclusions in Stages 1–3 are dominated by the H2O–CO2 type, and most of them contain liquid H2O and liquid CO2 at room temperature. The melting temperatures (Tm-CO2 = −82.1°C to −57.5°C) of solid CO2 in Stage 1 are relatively low. The values of Tm-CO2 in Stages 2–3 are quite close, with ranges of −60.5°C to −56.5°C and −59.2°C to −58.6°C, respectively. The melting temperatures of clathrate in Stages 1–3 are −2.7°C to +7.8°C, −5.5°C to +7.8°C, and +3.7°C to +7.2°C. The homogenization temperatures of the CO2 phase in the H2O–CO2 inclusions of the three stages are measured as −7.5°C to +31.7°C, −7.5°C to +29.3°C, and 7.1°C to +24.1°C. The total homogenization temperatures in Stages 1–3 are 180°C–394°C, 202°C–305°C, and 224°C–271°C, with salinities of 4.3 wt.%–18.2 wt% NaCl, 4.3 wt.%–20.0 wt% NaCl, and 5.3 wt.%–11.0 wt% NaCl, respectively. The laser Raman spectroscopy results show that the CO2–H2O inclusions in the quartz veins contain abundant CO2 and CH4. The SRXFR results show that most of the elements, especially As, Te, and Cu, are more enriched in liquid CO2 than in liquid H2O. The elements of Au, Fe, Ni, Cu, and Pb have higher concentrations in H2O–CO2-type fluid inclusions in Stage 2 than other fluid inclusions in Stages 1–2, suggesting that gold mineralization is closely related to CO2-rich fluids. During the fluid evolution process, fluid immiscibility is an important mineralization mechanism of gold. The increase in CO2 and CH4 and the decrease in the fluid temperature might promote fluid immiscibility.

Nondestructive Mineral Imaging of Chinese Chive Leaves Withered by Physiological Damage Using Microbeam Synchrotron Radiation X-Ray Fluorescence Analysis.

A significant problem encountered in Chinese chives (Allium tuberosum) grown in greenhouses is the reduction in the yield and quality due to symptoms of withered leaf tips. Withered leaf tips of three Chinese chive cultivars were nondestructively analyzed by microbeam synchrotron radiation X-ray fluorescence (μ-SR-XRF) imaging. Dead, wilting, and healthy parts of the leaves exhibited significant variations in the mineral composition. The Ca/K X-ray intensity ratios were significantly increased with the degree of withering.

法科学のための綿埃の放射光 XRF 分析

法科学のための綿埃の放射光 XRF 分析

Metallogenesis and fluid evolution of the Huangtupo Cu–Zn deposit, East Tianshan, Xinjiang, NW China: Constraints from ore geology, fluid inclusion geochemistry, H–O–S isotopes, and U–Pb zircon, Re–Os chalcopyrite geochronology

The recently discovered Huangtupo Cu–Zn deposit is located in the Dananhu–Tousuquan arc, East Tianshan, NW China. Orebodies are hosted in volcano-sedimentary rocks of the Late Ordovician–Early Silurian Daliugou Formation. The metallogenic physicochemistry, ore-forming fluids, and metallogenesis of the deposit were investigated through orebody features, fluid inclusion microthermometry, laser Raman spectroscopy, and synchrotron-radiation X-ray fluorescence (SRXRF). The results indicate that the deposit includes an upper sedimentary exhalative ore belt (stage I) as well as a lower vein-stockwork ore belt in a hydrothermal fluid supply channel (stage II) associated with silicification, chloritization, epidotization, pyrophyllitization, and beresitization alteration. The Re–Os isochron age of 429.5 ± 10 Ma obtained from primary chalcopyrite. The LA-ICP-MS zircon U–Pb age of 423.3 ± 2.9 Ma for the host hangingwall tuff. Fluid inclusion (FI) microthermometry and geological characteristics were applied to constrain hydrothermal processes and ore genesis. Quartz and barite were collected from the massive sulfide and vein ores for FI study. Four types of FI were identified: liquid-rich L-type, vapor-rich V-type, daughter-mineral-bearing S-type, and C-type containing CO2–H2O. Stage I barite FIs yield homogenization temperatures of 232–364 °C (peak value 265 °C), with salinities of 4.85–10.94 wt% NaCl equiv., whereas stage II quartz FIs yield temperatures of 270–400 °C (peak value 350 °C), with salinities of 2.41–13.72 wt% NaCl equiv (peak value 6.28 wt%). Laser Raman spectroscopy analyses of FI gas compositions indicate that the FIs contain mainly H2O with minor CO2 and N2. Initial ore-forming fluids comprise a medium-high-temperature, low-salinity system of hot evolved seawater that was cooled and diluted by mixing with cold seawater. Fluid mixing and local boiling would have facilitated mineralization. SRXRF analyses indicate that the liquid phase is enriched in Cu and Zn. The δ34S values of sulfide indicate that the sulfur was derived from the magma (host volcanic rocks). Oxygen and hydrogen isotopic data also imply that the ore-forming fluids were mainly derived from deep circulation of seawater, and mixed with minor magmatic fluids. The estimated trapping pressures for vein-stockwork mineralization fluids range from 20 to 60 bar (average 40 bar) at a depth of ~0.4 km. The ore fluids ascenting along faults and fracture networks at or near the seafloor played important roles in oreforming processes of the Huangtupo VMS Cu–Zn deposit.

Synchrotron Radiation X-ray Fluorescence Analysis of Excavated Amber for Provenance Study

Synchrotron Radiation X-ray Fluorescence Analysis of Excavated Amber for Provenance Study

Elemental composition of PM0.25 collected in an urban site of Argentina: A first case study

A total of 175 aerosol samples were collected during the winter-spring months of 2014–2015 in Córdoba, Argentina. The samples were collected in five size fractions that ranged from <0.25 to 10 μm using a SIOUTAS impactor in a 6-h period and analyzed by synchrotron radiation X-ray fluorescence to obtain elemental aerosol mass concentrations for As, Ca, Co, Cr, Cu, Fe, K, Mn, Ni, Pb, Si, S, Ti, V, and Zn. An analysis of the distribution of the elements in the different collected fractions was performed to infer the most likely sources of particulate matter. From the analysis, it was found that the particulate matter fraction smaller than 0.25 μm was mostly affected by emissions from traffic and combustion, while the particulate matter fraction ranging from 2.5 to 10 μm was mostly influenced by re-suspension of road dust. In addition, the results indicated the presence of Si, typically found in coarse particulate matter and in large amounts in particles smaller than 0.25 μm. To infer the sources of aerosols causing the deterioration of air quality, principal component analysis was performed. The smallest particles, due to their toxicity, are likely to produce more adverse health effects than larger size fractions. These results show the need to monitor their atmospheric emissions in order to preserve air quality. Synchrotron radiation X-ray fluorescence analysis of the elemental composition of particles smaller than 0.25 μm in Córdoba city constitutes the first contribution to the knowledge base of the concentrations of toxic metals in this size fraction. These results are relevant because there is a lack of data in South American cities.

Selenium decreases methylmercury and increases nutritional elements in rice growing in mercury-contaminated farmland

Methylmercury (MeHg) in rice grains grown in Hg-contaminated areas has raised environmental health concerns. Pot experiments found that selenium (Se) could reduce MeHg levels in rice grains. However, relatively high levels of Se (up to 6 mg/kg) were applied in these pot experiments, which may have adverse effects on the soil ecology due to the toxicity of Se. The aims of this work were thus to study 1) the effect of low levels of Se on the accumulation and distribution of Hg, especially MeHg, in rice plants grown in a real Hg-contaminated paddy field and 2) the effect of Se treatment on Se and other nutritional elements (e.g., Cu, Fe, Zn) in grains. A field study amended with different levels of Se was carried out in Hg-contaminated paddy soil in Qingzhen, Guizhou, China. The levels of MeHg and total Hg were studied using cold vapor atomic fluorescence spectrometry (CVAFS) and inductively coupled plasma mass spectrometry (ICP-MS). The distribution and relative quantification of elements in grains were examined by synchrotron radiation X-ray fluorescence analysis (SR-XRF). This field study showed that low levels of Se (0.5 μg/mL, corresponding to 0.15 mg Se/kg soils) could significantly reduce total Hg and MeHg in rice tissues. Se treatment also reduced Hg distribution in the embryo and endosperm and increased the levels of Fe, Cu, Zn and Se in grains and especially embryos. This field study implied that treatment with an appropriate level of Se is an effective approach to not only decrease the level of MeHg but to also increase the levels of nutritional elements such as Fe, Cu, Zn and Se in rice grains, which could bring beneficial effects for rice-dependent residents living in Hg-contaminated areas.

Synchrotron Radiation X-ray Fluorescence Analysis of Inks of Ballpoint Pens and Rollerball Pens for Criminal Investigation

Synchrotron Radiation X-ray Fluorescence Analysis of Inks of Ballpoint Pens and Rollerball Pens for Criminal Investigation

Quantitation and distribution of metallic elements in sequestra of medication-related osteonecrosis of jaw (MRONJ) using inductively coupled plasma atomic emission spectroscopy and synchrotron radiation X-ray fluorescence analysis.

Medication-related osteonecrosis of the jaw (MRONJ) is a serious adverse effect of antiresorptive agents like bisphosphonates. Abnormal concentrations of various trace metallic elements contained in bone minerals have been associated with MRONJ. In this study, we focused on trace metallic elements contained in the MRONJ sequestrum; their content and distribution were compared to those in osteomyelitis and non-inflammatory bones using inductively coupled plasma atomic emission spectroscopy (ICP-AES) and synchrotron radiation X-ray fluorescence analysis (SR-XRF). On ICP-AES analyses, various trace elements (Co, Cr, Cu, Fe, K, Mg, Ni, Sb, Ti, V, Pb) were significantly more in MRONJ sequestra than non-inflammatory bones. The Cu content was significantly higher in MRONJ sequestra than osteomyelitis and non-inflammatory bones. The Cu content in MRONJ sequestra was high even after decalcification. Additionally, Cu was distributed along the trabecular structures in decalcified MRONJ specimens, as observed using SR-XRF analysis. Therefore, this study was indicative of the characteristic behavior of Cu in MRONJ.

Annual Sedimentary Record From Lake Donguz-Orun (Central Caucasus) Constrained by High Resolution SR-XRF Analysis and Its Potential for Climate Reconstructions

Bottom sediments of the proglacial Lake Donguz-Orun situated at ~2500 m a.s.l. in the Elbrus Region (Central Caucasus) reveal regular laminae, characteristic of proglacial varved lakes. This is the first laminated sediment sequence recorded in the region. However, visual counting of the layers was restricted due to partial indistinctness of the lamination. In order to confirm the annual sedimentary cyclicity and proceed with annually resolved data, in addition to the visual identification we used high resolution geochemical markers. The upper 160 mm of the sediment core were scanned at 200 µm intervals using synchrotron radiation X-ray fluorescence analysis (SR-XRF). Additional ultrahigh resolution scanning at 30 µm increments was employed for the upper 20 mm of the core. The Rb/Sr and Zr/Rb ratios are interpreted to record annual changes in grain-size. Based on this geochemical assessment, we identified 88 annual layers covering the interval between 1922 and 2010, while visually we have been able to identify between 70 and 100 layers. The correctness of the geochemical results is confirmed by mean accumulation rates assessed by 137Cs and 210Pb dating. Cross-correlation between the ring width of local pine chronology and the layer thickness, identified as a distance between the annual Rb/Sr peaks, allowed for the accurate dating of the uppermost preserved year of the sediment sequence (AD 2010). Annually averaged elemental data were then compared with regional meteorological observations, glacier mass balance and tree-ring chronologies. The comparison revealed notable conformities: content of bromine is positively correlated with annual temperatures (r=0.41, p<0.01), content of terrigenous elements (major elements with the origin in watershed rocks) is positively correlated (up to r=0.44, p<0.01) with annual precipitation. A high statistically significant negative relationship is observed between the concentrations of terrigenous elements and tree-ring width of local pine chronology (up to r=-0.56, p<0.01). Taken together, these data point to a common composite climatic signal in the two independent records (lake sediments and tree rings) and confirm that the laminae represent annual layers (i.e., varves). These findings open opportunities for high resolution multiproxy climate reconstructions 300-350 years long using the longer sediment core and tree-ring records.

放射光X線分析による北海道地方の法科学土砂データベースの構築

The purpose of the present study is to construct a nation-wide forensic soil database, which allows for the identification of soil evidence based on heavy element and heavy mineral signatures determined by two synchrotron radiation (SR) X-ray techniques, i.e., a high-energy synchrotron radiation X-ray fluorescence analysis and a synchrotron-radiation X-ray powder diffraction analysis, respectively. The heavy element and heavy mineral compositions of the stream sediments collected at 3024 points located all over Japan were measured by the two SR X-ray techniques. The present paper focuses on a regional characterization of the sediments collected from the Hokkaido areas. The concentrations of heavy elements and heavy minerals in the Hokkaido areas were visualized as maps that enable us to compare the heavy element and heavy mineral compositions with the geological context of the samples. Based on a hierarchical cluster analysis using the semi-quantitative compositions of the heavy minerals, we could successfully classify the sediments into six groups corresponding to their background geologies. A Bonferroni multiple comparison demonstrated that these six groups also have significant differences in the heavy element composition. From these examinations, we could demonstrate that detailed regional identification of unknown samples is possible by analyzing both heavy element and heavy mineral compositions of each sample.

放射光蛍光 X 線分析を用いたポリエステル白色単繊維の非破壊異同識別

This study has revealed the advantages of synchrotron radiation X-ray fluorescence analysis (SR-XRF) utilizing 12 keV X-rays concentrated with polycapillary x-ray optics for nondestructive discrimination of polyester white single fibers. Twenty kinds of polyester white single fibers collected from 11 automobile trunk mats and 9 clothes were used as analysis samples. Titanium derived from TiO2 delustering agents, Ca derived from CaCO3 fillers, Sb and Ge derived from polymerization catalysts, elements such as Mn, Co, Ni and Cu derived from transesterification catalysts could be detected from polyester white single fibers. The elements detected can be used as important indexes to characterize the samples. In order to discriminate single fibers for clothes in which Ti and Sb were only detected, it has been suggested that comparison of x-ray intensity ratios of Sb Lα,β/Ti Kβ is effective. This technique should provide an effective approach to nondestructive discrimination of polyester white single fibers.

Cellular localization of uranium in the renal proximal tubules during acute renal uranium toxicity.

Renal toxicity is a hallmark of uranium exposure, with uranium accumulating specifically in the S3 segment of the proximal tubules causing tubular damage. As the distribution, concentration and dynamics of accumulated uranium at the cellular level is not well understood, here, we report on high-resolution quantitative in situ measurements by high-energy synchrotron radiation X-ray fluorescence analysis in renal sections from a rat model of uranium-induced acute renal toxicity. One day after subcutaneous administration of uranium acetate to male Wistar rats at a dose of 0.5 mg uranium kg(-1) body weight, uranium concentration in the S3 segment of the proximal tubules was 64.9 ± 18.2 µg g(-1) , sevenfold higher than the mean renal uranium concentration (9.7 ± 2.4 µg g(-1) ). Uranium distributed into the epithelium of the S3 segment of the proximal tubules and highly concentrated uranium (50-fold above mean renal concentration) in micro-regions was found near the nuclei. These uranium levels were maintained up to 8 days post-administration, despite more rapid reductions in mean renal concentration. Two weeks after uranium administration, damaged areas were filled with regenerating tubules and morphological signs of tissue recovery, but areas of high uranium concentration (100-fold above mean renal concentration) were still found in the epithelium of regenerating tubules. These data indicate that site-specific accumulation of uranium in micro-regions of the S3 segment of the proximal tubules and retention of uranium in concentrated areas during recovery are characteristics of uranium behavior in the kidney.

Infiltration of trace metal ions in the oral mucosa of a rat analyzed using SRXRF, XAFS, and ICP-MS.

Although the accumulation and distribution of metals from metallic orthodontic appliances in the oral mucosa have been studied extensively, they remain unclear because their concentration is quite low. In this study, metal specimens (Ni, Ni-Ti, and Co-Cr) were sutured in the unilateral oral mucosa of rats, and the distribution of the eluted elements in the mucosal tissue was estimated using inductively coupled plasma mass spectrometry (ICP-MS) and synchrotron radiation X-ray fluorescence analysis (SR-XRF). While the infiltrations of Ni, Co, and Cr into the oral mucosal connective tissue were observed with SR-XRF, significant increases were only found in Ni from the pure Ni group and Cr from the Co-Cr group. Furthermore, Ni and Co were estimated as hydrated ions while Cr was estimated in oxide form through X-ray absorption fine structure (XAFS) analysis.

A Study on Distribution and Chemical Speciation of Lead in Corn Seed Germination by Synchrotron Radiation X-ray Fluorescence and Absorption Near Edge Structure Spectrometry

Synchrotron radiation X-ray fluorescence analysis technology (SRXRF) can effectively reduce the detection limit for the determination of heavy metal elements. The technique is especially suitable for in situ nondestructive analysis of biological samples with low contents. By corn seed germination test, and combining with SRXRF technique, the effects of Pb on corn seed germination and Pb micro-distribution in the corn seed were studied. X-ray absorption near edge structure (XANES) technique was also used to analyze the Pb chemical speciation in different parts of corn seed. The above experiments were carried out for understanding the absorption and transformation mechanism of Pb by corn seeds. The results showed that the germination rate, bud length and root length decreased with the increasing contents of Pb. The analysis of variance showed that P-value of the germination rate, bud length and root elongation of corn seeds which were exposed to different concentration of Pb were 2.0 × 10−3, 1.4 × 10−4 and 2.4 × 10−8 respectively, suggesting there were highly significant differences during this three indicators and the content of Pb. In addition, the inhibition effect on root growth was greater. The results of SRXRF analysis showed that Pb was mainly enriched in episperm and embryo, which would inhibit embryonic develop into bud and root. Moreover, the results showed that all samples including root, shoot and the different part of seed had the same Pb-LIII (13035 eV) XANES spectra and Pb speciation. The linear combination fitting results indicated that the lead phosphate chloride and lead stearate accounted for 74.3% and 24.2% respectively, suggesting that the main Pb speciation in corn was lead phosphate chloride which deposited inside of corn, and a few combined with carboxylic to form organic lead.

Immiscibility of magmatic fluids and their relation to Mo and Cu mineralization at the Bangpu porphyry deposit, Tibet, China

The coexistence of aqueous fluid inclusions and silicate melt inclusions in quartz phenocrysts from porphyrites at the Bangpu porphyry Mo–Cu deposit, Tibet, China were examined to characterize the immiscibility processes during the magmatic to hydrothermal transition. The physical and chemical environment during crystallization of the magmas has been reconstructed on the basis of microthermometric experiments and trace element microanalysis. Compositions of melt and brine fluid phases are determined using Synchrotron radiation X-ray fluorescence analysis, SEM–EDS and Laser Raman spectroscopy analyses. Brine fluids were directly exsolved by a crystallizing melt, and the simultaneous entrapment of volatile-rich (brine fluid) and volatile-poor immiscible phases (silicate melt) occurred at 670–700°C and 1.6–1.95kbar when the magma had H2O contents between 5 and 6wt% and crystal contents of 60–80%. A later low-density fluid with a higher Mo concentration exsolved after about 80–90% crystallization had occurred. This fluid contained significant concentrations of Cl, Na, K, Ca, Fe, Cu, Zn, Rb, and small amounts of Mn, Br and Pb. Immiscibility of magmatic fluids can lead to different metal partitioning behaviors between residual melt and volatile phases, which generate variable metal ratios. Copper was partitioned preferentially into the brine phase, in contrast to the behavior observed in other porphyry Cu deposits. Ore deposition by a dense brine could explain the partially deep Cu mineralization. Condensation of brine from a later low-density parental fluid could be an efficient mechanism to concentrate shallow Cu mineralization and broadly distributed Mo mineralization. The source of the Mo mineralizing fluids probably was a particularly large magma chamber that crystallized and fractionated at depth greater than upper continental crust level.

Evaluation of different synchrotron beamline configurations for X-ray fluorescence analysis of environmental samples.

Synchrotron radiation X-ray fluorescence (SR-XRF) is a powerful elemental analysis tool, yet synchrotrons are large, multiuser facilities that are generally not amenable to modification. However, the X-ray beamlines from synchrotrons can be modified by simply including X-ray filters or removing monochromators to improve the SR-XRF analysis. In this study, we evaluated four easily applied beamline configurations for the analysis of three representative environmental samples, namely a thin aerosol sample, an intermediate thickness biological sample, and a thick rare earth mineral specimen. The results showed that the "white beam" configuration, which was simply the full, polychromatic output of the synchrotron, was the optimal configuration for the analysis of thin samples with little mass. The "filtered white beam" configuration removed the lower energy X-rays from the excitation beam so it gave better sensitivity for elements emitting more energetic X-rays. The "filtered white beam-filtered detector" configuration sacrifices the lower energy part of the spectrum (<15 keV) for improved sensitivity in the higher end (∼26 to 48 keV range). The use of a monochromatic beam, which tends to be the standard mode of operation for most SR-XRF analyses reported in the literature, gave the least sensitive analysis.

Uranium dynamics and developmental sensitivity in rat kidney

Renal toxicity is the principal health concern after uranium exposure. Children are particularly vulnerable to uranium exposure; with contact with depleted uranium in war zones or groundwater contamination the most likely exposure scenarios. To investigate renal sensitivity to uranium exposure during development, we examined uranium distribution and uranium-induced apoptosis in the kidneys of neonate (7-day-old), prepubertal (25-day-old) and adult (70-day-old) male Wistar rats. Mean renal uranium concentrations increased with both age-at-exposure and exposure level after subcutaneous administration of uranium acetate (UA) (0.1-2 mg kg(-1) body weight). Although less of the injected uranium was deposited in the kidneys of the two younger rat groups, the proportion of the peak uranium content remaining in the kidneys after 2 weeks declined with age-at-exposure, suggesting reduced clearance in younger animals. In situ high-energy synchrotron radiation X-ray fluorescence analysis revealed site-specific accumulation of uranium in the S3 segment of the proximal tubules, distributed in the inner cortex and outer stripe of the outer medulla. Apoptosis and cell loss in the proximal tubules increased with age-at-exposure to 0.5 mg kg(-1) UA. Surprisingly, prepubertal rats were uniquely sensitive to uranium-induced lethality from the higher exposure levels. Observations of increased apoptosis in generating/re-generating tubules particularly in prepubertal rats could help to explain their high mortality rate. Together, our findings suggest that age-at-exposure and exposure level are important parameters for uranium toxicity; uranium tends to persist in developing kidneys after low-level exposures, although renal toxicity is more pronounced in adults.