μ-XRF Mapping Research Articles

Rare earth element (REE) speciation in municipal solid waste incineration ash

A robust and sustainable supply of rare earth elements (REE) is critically needed for clean-energy technologies, which has stimulated substantial interests in REE recovery from waste streams. Municipal solid waste incineration ash (MSWIA) was recently recognized as a potentially important REE resource, yet REE speciation in MSWIA remains poorly understood. This study employed synchrotron X-ray spectroscopy and microscopy techniques to elucidate the speciation of representative REE (Y, Ce, and Nd) in different MSWIA samples. Linear combination fitting of bulk X-ray absorption near edge structure (XANES) data indicated that Y-bearing Al/Fe oxides and phosphates are the primary Y-hosting phases. Micro-XANES of individual Y-containing particles identified by micro X-ray fluorescence (μXRF) mapping revealed notably different Y speciation at micro-scale from the bulk, consistent with the highly heterogeneous nature of MSWIA samples. The main REE-bearing phases in different size-fractionated MSWIA are similar: Y and Nd as oxides and xenotime/monazite, and Ce as apatite and monazite. Our results provide important insights for designing pre-screening processes (e.g., density separation) and optimizing extraction methods (e.g., pH, use of ligands) for cost-effective REE recovery from MSWIA.

Lead Speciation, Bioaccessibility, and Sources for a Contaminated Subset of House Dust and Soils Collected from Similar United States Residences.

Residential lead (Pb) exposure is of critical concern to families globally as Pb promotes severe neurological effects in children, especially those less than 5 years old, and no blood lead level is deemed safe by the US Center for Disease Control. House dust and soils are commonly thought to be important sources of Pb exposure. Probing the relationship between house dust and soil Pb is critical to understanding residential exposure, as Pb bioavailability is highly influenced by Pb sources and/or species. We investigated paired house dust and soil collected from homes built before 1978 to determine Pb speciation, source, and bioaccessibility with the primary goal of assessing chemical factors driving Pb exposure in residential media. House dust was predominately found to contain (hydro)cerussite (i.e., Pb (hydroxy)carbonate) phases commonly used in Pb-based paint that, in-turn, promoted elevated bioaccessibility (>60%). Pb X-ray absorption spectroscopy, μ-XRF mapping, and Pb isotope ratio analysis for house dust and soils support house dust Pb as chemically unique compared to exterior soils, although paint Pb is expected to be a major source for both. Soil pedogenesis and increased protection from environmental conditions (e.g., weathering) in households is expected to greatly impact Pb phase differences between house dust and soils, subsequently dictating differences in Pb exposure.

Investigation of the accuracy of a portable 109Cd XRF system for the measurement of iron in skin

We have previously reported the design of a portable 109Cd x-ray fluorescence (XRF) system to measure iron levels in the skin of patients with either iron overload disease, such as thalassemia, or iron deficiency disease, such as anemia. In phantom studies, the system was found to have a detection limit of 1.35 μg Fe per g of tissue for a dose of 1.1 mSv. However, the system must provide accurate as well as precise measurements of iron levels in the skin in order to be suitable for human studies. The accuracy of the system has been explored using several methods. First, the iron concentrations of ten pigskin samples were assessed using both the portable XRF system and ICP-MS, and the results were compared. Overall, it was found that XRF and ICP-MS reported average values for iron in skin that were comparable to within uncertainties. The mean difference between the two methodologies was not significant, 2.5 ± 4.6 μg Fe per g. On this basis, the system could be considered accurate. However, ICP-MS measurements reported a wider range of values than XRF, with two individual samples having ICP-MS results that were significantly elevated (p < 0.05) compared to XRF. Synchrotron μXRF maps of iron levels in pigskin were acquired on the BioXAS beam line of the Canadian Light Source. The μXRF maps indicated two important features in the distribution of iron in pigskin. First, there were small areas of high iron concentration in the pigskin samples, that were predominantly located in the dermis and hypodermis at depths greater than 0.5 mm. Monte Carlo modelling using the EGS 5 code determined that if these iron ‘hot spots’ were located towards the back of the skin at depths greater than 0.5 mm, they would not be observed by XRF, but would be measured by ICP-MS. These results support a hypothesis that iron levels in the two samples that reported significantly elevated ICP-MS results compared to XRF may have had small blood vessels at the back of the skin. Second, the synchrotron μXRF maps also showed a narrow (approximately 100μm thick) layer of elevated iron at the surface of the skin. Monte Carlo models determined that, as expected, the XRF system was most sensitive to these skin layers. However, the simulations found that the XRF system, when calibrated against homogenous water-based phantoms, was found to accurately measure average iron levels in the skin of normal pigs despite the greater sensitivity to the surface layer. The Monte Carlo results further indicated that with highly elevated skin surface iron levels, the XRF system would not provide a good estimate of average skin iron levels. The XRF estimate could, with correction factors, provide a good estimate of the iron levels in the surface layers of skin. There is limited data on iron distribution in skin, especially under conditions of disease. If iron levels are elevated at the skin surface by diseases including thalassemia and hemochromatosis, this XRF device may prove to be an accurate clinical tool. However, further data are required on skin iron distributions in healthy and iron overload disease before this system can be verified to provide accurate measurements.

Microscale heterogeneity of phosphorus species associated with secondary mineral phases in the B horizons of two boreal Podzols

Poorly crystalline Al and Fe minerals have high sorption capacities for phosphate anions. However, there is still uncertainty about the molecular-level distribution of phosphorus (P) species between Al and Fe mineral phases, which can be relevant for bioavailability. The present study employed synchrotron X-ray microscopic techniques to distinguish between Al- and Fe-associated P phases in two Podzol B horizons (Flakaliden and Skogaby). First, P species were clustered into major groups depending on the main element association (Al-P, Fe-P, Ca-P + organic P) according to the color of P-containing spots in the tricolor μ-XRF quantitative maps that combined P, Al, and Fe fluorescence intensities. Second, the results were analyzed using quantitative linear combination fitting (LCF) of the P K-edge μ-XANES spectra. Third, in cases when the results diverged, a careful visual comparison between the diagnostic features of the XANES spectra of the samples and the reference standards was made. In 45 of 54 investigated spots, the color method and XANES-LCF produced consistent results. In 2 spots where the results were inconsistent, the diagnostic features of the XANES spectra agreed with the color method but not with XANES-LCF. In 39 of the 47 spots where the major P phase could be identified, Al-P was found to predominate. Ca-P was the major phase in 5 spots, Fe-P in 2, and organic P in 1. Most of the Al-P probably consisted of PO4 adsorbed to imogolite-type materials (ITM), as evidenced by oxalate extraction and Fourier Transform Infrared (FTIR) spectroscopy, although at Skogaby, adsorbed organic P may have played an important additional role. Overall, the P speciation showed substantial spatial heterogeneity, particularly in the upper B horizon of the Skogaby soil and in the lower B horizon of the Flakaliden soil. In conclusion, Al-P, particularly ITM-adsorbed PO4, is the main P phase in the B horizons of the studied Podzols, which may have implications for bioavailability as ITM is more easily dissolved than Fe oxides. Also, the combination of XANES-LCF, colors of the μ-XRF maps, and diagnostic features of the XANES spectra led to robust estimates of the major P phases in soil microsites.

Unravelling the role of iron and manganese oxides in colouring Late Antique glass by micro-XANES and micro-XRF spectroscopies

This research aims to understand colouring technologies in 5th–7th centuries glass imported to Atlantic Britain by correlating the iron (Fe) and manganese (Mn) ratios and oxidation states with colour. Despite having a similar matrix chemical composition and concentrations of Fe and Mn oxides, these vessels display different colours (from green to yellow/amber, sometimes with purple streaks). Colour changes can be induced by controlling the reduction-oxidation reactions that occur during glass production, which are influenced by the raw materials, furnace and melt atmosphere, and recycling. To evaluate these parameters, reference glasses were prepared, following the composition of Late Antique archaeological glass recovered from Tintagel (UK) and Whithorn (UK). A corpus of archaeological and experimental glass samples was analysed using bulk Fe and Mn K-edge x-ray absorption near edge structure (XANES) spectroscopy, micro-XANES and micro x-ray fluorescence (μ-XRF) at beamline ID21, at the European Synchrotron Radiation Facility. Fe and Mn XANES spectra of the archaeological glass indicate that Fe and Mn are in a similar oxidation state in all the yellow samples, predominantly Fe3+ and Mn2+. No detectable difference in Mn and Fe oxidation state occurs in the purple streaks compared to the yellow glass bulk but μ-XRF maps of the distribution of Fe and Mn show that Mn is more concentrated in the purple streaks. This indicates that the purple colour of the streaks is mainly due to a higher Mn/Fe ratio and persistence of more oxidised manganese in the purple areas, even though it is difficult to detect. Many archaeological fragments appear pale green in transmitted light but amber in reflected light. XANES studies detected the presence of surface layers where manganese is more oxidised. This layer is believed to scatter transmitted and reflected light differently and might be responsible for the optical features of the archaeological glass.

Potentially toxic elements speciation in bottom ashes from a municipal solid waste incinerator: A combined SEM-EDS, µ-XRF and µ-XANES study

Bottom Ashes from Municipal Solid Waste Incinerators and Waste to Energy plants represent an interesting source of secondary raw materials for many applications, like urban mining and inclusion in concrete, and road pavement. However, Bottom Ashes may contain potentially toxic elements, whose actual toxicity depends essentially on their oxidation state and mineralogical environment. For this reason, a representative sample of bottom ashes from Parma Waste to Energy plant has been selected to investigate the chemical speciation of Cr, Ni, Pb, Co, Zn and Cu by means of complementary techniques: Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS), micro X-Ray Fluorescence (µ-XRF) mapping and X-Ray Absorption Near Edge Structure (XANES) measurements by synchrotron radiation. This multi-technique approach allowed to obtain a general image of the mineralogical and chemical environment in which these elements are found. SEM-EDS analyses show the presence of Zn and Pb both in minerals and in glass matrix. Cr has been detected in the form of oxide and in spinel structure (chromite) whereas Co and Cu are found as alloy or metal inclusions. µ-XRF mapping reveals that Cu, Ni and Cr are generally associated to Na, K and Si suggesting their presence in glass matrix. XANES investigations exhibit that Cu has a variable oxidation state that suggesting its presence in the form of oxide, hydroxide, acetate and metal. Zn is mainly found as +II and in a number of different phases (including Zn-carbonates, in agreement with SEM-EDS data). Cr has been found only as +III, with XANES features resembling those of chromite, whereas as +VI was never identified. Ni and Co were found either as metal form and oxides. Pb spectra show a good match with oxides.

X-ray Absorption Spectroscopy Reveals Mechanisms of Calcium and Silicon Fouling on Reverse Osmosis Membranes Used in Wastewater Reclamation

Reverse osmosis (RO) is widely employed to provide clean water from nontraditional sources (e.g., seawater or municipal wastewater). One of its key challenges is membrane fouling, which leads to reduced flux and increased operational costs. Despite its practical relevance, fundamental understanding of membrane fouling is limited. Toward this end, we investigated calcium (Ca) and silicon (Si) fouling under real RO feed conditions using μ-X-ray fluorescence (μ-XRF) mapping and μ-X-ray absorption near-edge fine structure (μ-XANES) spectroscopy. These techniques are distinctly suited to identify the spatial distribution and (local) chemical speciation of foulants, thereby providing unique insight into the mechanisms of fouling under realistic conditions. Specifically, we investigated RO membranes harvested from a pilot-scale RO system operated at the Orange County Water District (OCWD) Groundwater Replenishment System (GWRS) Advanced Water Purification (AWP) Facility, which received the same feed water as the full-scale plant. Both Ca and Si were found to be abundant in the fouling layer. Despite the use of a commercial antiscalant to inhibit mineral formation, several Ca minerals were present in the fouling layer as minority species, including sulfates, phosphates, and carbonates; most of these minerals were found in particles that were aligned with the feed spacer used to separate the membranes. In contrast, organic-bound Ca and silica occurred across the entire membrane. Our work provides novel insight into the synergistic mechanism of RO fouling by Ca, Si, and organics on RO membranes.

Molecular-level investigation on removal mechanisms of aqueous hexavalent chromium by pine needle biochar

Pine needle biochar produced via oxygen-limited pyrolysis at 800 °C for 2 h was used for removing aqueous hexavalent chromium [Cr(VI)] from water. The optimality of the pseudo-second order kinetic model indicated the chemisorption dominated the removal process. Strong acid environment (pH = 2.0) was more conductive to Cr(VI) removal. The functional groups (C–O, O–C–O, C = O) on biochar contributed to Cr(VI) elimination from aqueous solution. The governing removal mechanisms involved electrostatic attraction, reduction, and complexation. Especially, confocal micro-X-ray fluorescence (μ-XRF) mapping indicated that Cr ions and functional groups were primarily distributed on the surface of biochar. This study firstly provided a deep interpretation of Cr speciation and spatial distribution on pine needle biochar, which provided important information on removal mechanisms of Cr(VI) by pine needle biochar.

Factors controlling tungsten mobility in W[sbnd]Cu skarn tailings

Few studies have addressed the mobility of tungsten in mine waste, which could act as a point source for metal leaching of this potentially toxic metal. This study examines the behavior of tungsten in acidic floodplain tailings and circumneutral impoundment tailings at the Cantung Mine in the Northwest Territories, Canada. In the Cantung deposit, tungsten is present as scheelite (CaWO4), copper is hosted in chalcopyrite (CuFeS2), and gangue mineralogy consists of abundant pyrrhotite (Fe1-xS), silicate minerals, and carbonate minerals. Samples of surface waters, tailings porewaters, and solid tailings samples were collected from Cantung Mine. For surface waters, both filtered (0.45 μm) and unfiltered aliquots were collected to compare dissolved and particulate element concentrations.Tungsten concentrations range from 5.8 to 30.0 μg/L in water samples with pH values between 7.1 and 8.1, whereas samples below pH 7.1 have concentrations below the detection limit of 0.1 μg/L. Tungsten and iron concentrations are both on average 1.7 times higher in unfiltered aliquots compared to filtered aliquots, suggesting that tungsten is transported as dissolved species but is also adsorbed to suspended Fe-oxyhydroxide minerals at neutral pH. Tailings were analyzed by scanning electron microscopy (SEM) paired with automated mineralogy software (MLA), synchrotron-based μX-ray diffraction and fluorescence (μXRD-XRF), and partial leach digestions with inductively coupled plasma mass spectrometry (cold and hot hydroxylamine hydrochloride, aqua regia, Li-metaborate fusion, and 4-acid digestion with HNO3-HClO4-HF-HCl). Samples from the impounded tailings and the highly oxidized Flat River Tailings distributed on the floodplain (FRT) have similar scheelite content (0.15 wt% and 0.21 wt%, respectively), and scheelite shows no evidence of alteration. Synchrotron-based μXRD of Fe-oxyhydroxide minerals in the FRT identified goethite (FeOOH) and lepidocrocite (γ-FeOOH) as products of pyrrhotite oxidation. Rare rims on pyrrhotite from the tailings impoundment have μXRD spectra consistent with hematite (Fe2O3) and maghemite (γ-Fe2O3). The μXRF maps of the hematite-maghemite rims have prominent tungsten peaks, which represent included scheelite grains and possibly structurally incorporated tungsten. The hydroxylamine leaches yield higher tungsten concentrations in tailings samples from the circumneutral impoundments than samples from the acidic FRT, suggesting the tailings impoundments have more tungsten that is associated with poorly crystalline and amorphous Fe-oxyhydroxide phases than the FRT. Over time, labile-hosted tungsten in the FRT may have been washed down the Flat River during Fe-oxyhydroxide recrystallization and high energy flooding events. These results indicate that scheelite has limited solubility in neutral or acid mine waters, and the mobility of the small amount of tungsten released is governed by the present of iron oxyhydroxide minerals, the transport of colloidal material in surface water, and the stability of the depositional environment.

Speciation and distribution of chromium (III) in rice root tip and mature zone: The significant impact of root exudation and iron plaque on chromium bioavailability

Evidence on the contribution of root regions with varied maturity levels in iron plaque (IP) formation and root exudation of metabolites and their consequences for uptake and bioavailability of chromium (Cr) remains unknown. Therefore, we applied combined nanoscale secondary ion mass spectrometry (NanoSIMS) and synchrotron-based techniques, micro-X-ray fluorescence (µ-XRF) and micro-X-ray absorption near-edge structure (µ-XANES) to examine the speciation and localisation of Cr and the distribution of (micro-) nutrients in rice root tip and mature region. µ-XRF mapping revealed that the distribution of Cr and (micro-) nutrients varied between root regions. Cr K-edge XANES analysis at Cr hotspots attributed the dominant speciation of Cr in outer (epidermal and sub-epidermal) cell layers of the root tips and mature root to Cr(III)-FA (fulvic acid-like anions) (58–64%) and Cr(III)-Fh (amorphous ferrihydrite) (83–87%) complexes, respectively. The co-occurrence of a high proportion of Cr(III)-FA species and strong co-location signals of 52Cr16O and 13C14N in the mature root epidermis relative to the sub-epidermis indicated an association of Cr with active root surfaces, where the dissolution of IP and release of their associated Cr are likely subject to the mediation of organic anions. The results of NanoSIMS (poor 52Cr16O and 13C14N signals), dissolution (no IP dissolution) and µ-XANES (64% in sub-epidermis >58% in the epidermis for Cr(III)-FA species) analyses of root tips may be indicative of the possible re-uptake of Cr by this region. The results of this research work highlight the significance of IP and organic anions in rice root systems on the bioavailability and dynamics of heavy metals (e.g. Cr).

Taking a look at the surface: μ-XRF mapping and fluorine K-edge μ-XANES spectroscopy of organofluorinated compounds in environmental samples and consumer products.

For the first time, μ-X-ray fluorescence (μ-XRF) mapping combined with fluorine K-edge μ-X-ray absorption near-edge structure (μ-XANES) spectroscopy was applied to depict per- and polyfluoroalkyl substance (PFAS) contamination and inorganic fluoride in sample concentrations down to 100 μg kg-1 fluoride. To demonstrate the matrix tolerance of the method, several PFAS contaminated soil and sludge samples as well as selected consumer product samples (textiles, food contact paper and permanent baking sheets) were investigated. μ-XRF mapping allows for a unique element-specific visualization at the sample surface and enables localization of fluorine containing compounds to a depth of 1 μm. Manually selected fluorine rich spots were subsequently analyzed via fluorine K-edge μ-XANES spectroscopy. To support spectral interpretation with respect to inorganic and organic chemical distribution and compound class determination, linear combination (LC) fitting was applied to all recorded μ-XANES spectra. Complementarily, solvent extracts of all samples were target-analyzed via LC-MS/MS spectrometry. The detected PFAS sum values range from 20 to 1136 μg kg-1 dry weight (dw). All environmentally exposed samples revealed a higher concentration of PFAS with a chain length > C8 (e.g. 580 μg kg-1 dw PFOS for Soil1), whereas the consumer product samples showed a more uniform distribution with regard to chain lengths from C4 to C8. Independent of quantified PFAS amounts via target analysis, μ-XRF mapping combined with μ-XANES spectroscopy was successfully applied to detect both point-specific concentration maxima and evenly distributed surface coatings of fluorinated organic contaminants in the corresponding samples.

Microscopic and geochemical analyses of the Tonian Longfengshan biota from the Luotuoling Formation (Hebei Province, North China) with taphonomic implications

The Tonian Longfengshan biota is among the earliest known fossil assemblages with a predominance of the benthic macroalgal fossil LongfengshaniaDu, 1982, which is well known for its blade, stipe, and holdfast differentiation. However, the microstructure and geochemical composition of these fossils are poorly understood. We documented the microscopic characteristics, mineralogy, and geochemistry of 29 fossil specimens from the Luotuoling Formation at the Longfengshan locality of Hebei Province, North China using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), micro X-ray fluorescence spectroscopy (μ-XRF), Raman spectroscopy, and X-ray Diffraction (XRD). SEM-EDS revealed that all fossil specimens are preserved as two-dimensional compressions that are composed of carbonaceous patches and also have high calcium content. Iron-rich clay minerals were additionally detected in association with the fossils. μ-XRF mapping confirmed the fossils’ high calcium content. Raman spectroscopy showed that carbonaceous patches are comprised of disordered organic carbon that has been altered by low grade metamorphism (<300 °C). XRD showed a homogenous mineralogy (dominated by quartz, feldspar, and muscovite with other minor e.g., kaolinite, smectite). Petrographic analysis revealed that microbial mats existed in the fossil-bearing shale, implying that benthic macroalga Longfengshania attached its holdfast in a sticky microbial mat that encrusted the sea-bed. Integration of these data suggested that the fossil-bearing silty shale was deposited in the subtidal zone below storm wave base. Iron-replete but sulfate-depleted porewater within sediments may have inhibited the degradation process of the Longfengshan macroalgae.

Distinguishing between seemingly identical inks using scanning µXRF and heat maps

• Stages of writing and correction can be identified thanks to material analysis. • Seemingly identical inks can be distinguished with use of imaging µXRF. • The application of XRF heat maps allows identification of altered portions of text. • Stratigraphy of seemingly identical materials can be unveiled by µXRF and heat maps. This study will present a new approach to distinguishing writing inks that have the same elemental compositions and visual appearances. The approach is based on displaying the intensity of elemental distributions as heat maps that represent data recorded with a scanning µX-ray fluorescence spectrometer. The heat maps present the data so as to facilitate digitally identifying and distinguishing between inks used to produce, correct, and reink two medieval Torah scrolls. As ritual objects, Torah scrolls had to be written in accordance with exacting standards that evolved over time. This requirement led to successive stages of modifications, sometimes over centuries. Both vitriolic and non-vitriolic inks used to modify Torah scrolls can be visually identical to each other. Furthermore, different non-vitriolic inks usually have an identical elemental composition. The solid material analysis evidence and its presentation as heat maps made it possible to discriminate between original and altered portions of text that in some cases would have been impossible. Our interdisciplinary work brought together conservation, material science, paleography, and philology to enable the identification of complex stratigraphy in multiple stages of production, correction, and reinking.

Synchrotron µ-XRF mapping analysis of trace elements in in-situ cultured Japanese red coral, Corallium japonicum.

Precious corals belong to the family Coralliidae (Cnidaria, Octocorallia), and their axis, which consists of high magnesian calcium carbonate, has long been used in jewelry. With its low growth rate and long lifespan, precious coral is a representative taxon of the vulnerable marine ecosystem. Due to years of overfishing, coral fishery has become a controversial issue. To estimate the growth rate and clarify the uptake process of trace elements in relation to the growth of the carbonate axis, Japanese red coral (Corallium japonicum) was cultured at a depth of 135 m off Takeshima Island, Kagoshima, Japan for 98 months and analyzed by microscopic X-ray fluorescence/soft X-ray photoabsorption (µ-XRF/XAS) speciation mapping. The growth rate was estimated to be 0.37 mm/year in diameter, and 10–11 growth rings were observed in a cross section of the axis. This estimated growth-rate value is the first ever to be obtained from the in-situ culture of Japanese precious coral. The fluctuation in water temperature near the in-situ-culture site was recorded for part of the culture period and then compared with the changes in the growth ring and the distribution of trace elements in a cross section of the coral axis during the same period. When the water temperature was increasing, the growth ring was light in color, sulfur and phosphorus concentrations were low, and magnesium was high. Conversely, a dark band in the growth ring, high sulfur and phosphorus, and low magnesium concentrations were observed when the water temperature was decreasing. In a cross section of the coral axis, the distribution of sulfur and magnesium from the center to the surface corresponded, respectively, to dark and light bands in the annual growth ring. Sulfur concentration was high in the dark band and low in the light band, while magnesium was negatively correlated with sulfur.

Micro- to nano-scale areal heterogeneity in pore structure and mineral compositions of a sub-decimeter-sized Eagle Ford Shale

Mineral and organic matter compositions & pore structures of fine-grained shale influence reservoir properties. To improve the understanding of spatial heterogeneity in core-sized samples, methods of microscale X-ray fluorescence (μXRF) mapping, (ultra-) small-angle x-ray scattering [(U)SAXS] and wide-angle X-ray scattering (WAXS) have been used to determine elemental, pore-structure variations at scales up to ~10 cm on two samples prepared at circular and rectangular orientations from a piece of Eagle Ford Shale outcrop in South Texas, USA. In addition, thin section petrography and field emission-scanning electron microscopy observations, X-ray diffraction (XRD), total organic carbon, and pyrolysis were utilized to investigate the potential spatial heterogeneity of pore types, mineral and organic matter compositions for cm-sized samples at both orientations. Overall, the siliceous‑carbonate mineral contents in these two samples (8 cm × 8 cm × 0.08 cm and 5 cm × 8 cm × 0.08 cm, in terms of width×length×thickness) of carbonate-rich Eagle Ford Shale vary between laminations at mm scales. For the circular sample, porosity and specific surface area (SSA) variations range from 0.82 to 3.04% and 1.51 to 14.1 m2/g, respectively. For the rectangular sample, values for porosity and SSA vary from 0.93 to 2.50% and 3.95 to 10.8 m2/g. By analyzing six selected sub-samples on each of two samples with (U)SAXS and XRD techniques, nm-sized pores are mainly interparticle ones in the higher calcite regions, where the porosity is also relatively lower, while the lower calcite regions consist of both interparticle and intraparticle pore types with higher porosity. Finally, the μXRF and (U)SAXS mappings are combined to generate porosity distribution maps to provide more insights about sample heterogeneity related to the laminations and fractures at our observational scales.

MET-post-IR IRSL luminescence dating of cobbles buried in fluvial terraces in the Northern Chinese Tian Shan

Cobbles can be used as an alternative to the conventionally employed sand-sized mineral luminescence dating. In piedmont environments, cobbles are much more abundant than sand-sized material. The IRSL 50 signal has been widely used in previous studies due to its greater sensitivity to exposure events. However, it is well known that the low temperature IRSL signal is more prone to fade than elevated temperature post-IR IRSL signal. In this study, to test the reliability and applicability of cobble sub-surface elevated temperature IRSL luminescence dating, six light-color granite cobbles and two sand-sized samples from silty sand lens were collected from a high terrace of Manas River on the northern piedmont of Chinese Tian Shan. A modified multi-elevated-temperature post-infrared infrared stimulated luminescence (MET-post-IR IRSL) protocol was applied. The age-temperature (A-T) plateau of MET-post-IR IRSL measurement was combined with the conventional age-depth (A-D) plateau in luminescence-depth profile to evaluate the resetting and fading of MET-post-IR IRSL signals. Uncertainties of grain-sizes of K-feldspar within solidified slices were also explored by μ-XRF mapping of potassium content. The A-T plateau was identified between MET-post-IR IRSL 170 and MET-post-IR IRSL 225 signals of one cobble, which suggested completeness of bleaching before burial and negligible anomalous fading during burial. This cobble yielded MET-post-IR IRSL 225 ages of 15.8 ± 2.6 ka and 19.0 ± 3.2 ka for top and bottom side, respectively. These MET-post-IR IRSL 225 ages were consistent with independent coarse-grained quartz MAM OSL ages (15.7 ± 3.6 ka and 14.8 ± 2.6 ka) of two sand-sized samples. The MET-post-IR IRSL 225 age of 16.0 ± 1.2 ka for the bottom side of another cobble was also consistent with the independent age, even without the A-T plateau. It was inferred to be caused by anomalous fading of MET-post-IR IRSL signals other than that stimulated at 225 °C by refering to the A-D plateau observed. Our results show that MET-post-IR IRSL measurement can be employed to determine the burial ages of cobbles. The A-T plateau, complemented with the A-D plateau, could be used to assess the reliability of burial ages of cobble luminescence dating from the view of bleaching and fading. • MET-post-IR IRSL measurement has advantages in judgement of fading and bleaching of rock slices. • Constraining the terrace ages using fluvial cobbles has great potential and prospects. • Evaluating the uncertainty of internal dose related to grain sizes variation of K-feldspar.

微小領域蛍光X線マッピングの応用：鉄コンクリーション内部に見られる鉄バンドの形成プロセスと移動速度の評価

Fe oxide Liesegang bands have often been observed in sedimentary and igneous rocks, and they are formed during weathering and alteration by water-rock interactions. In this study, micro-X-ray fluorescence (μ-XRF) mapping was used to study the Fe bands in an Fe oxide concretion from the Jurassic Navajo Sandstone in Utah, USA, to estimate the duration of their formation. Most of the peaks in Fe concentration are steeper on the inner side than on the outer side, which indicates a supply of ferrous ions (Fe2+) from outside the concretion. The precipitation of Fe oxide was controlled by pH buffering that resulted from a reaction between acidic water and alkaline pore water that formed through the dissolution of an earlier calcite concretion. The reaction rate within the Fe oxide concretion was estimated from the width of the Fe peaks and the expected diffusion coefficient for Fe through the rock matrix, and it was found to be no more than years to decades-faster than previously estimated. This demonstrates that μ-XRF mapping is a useful technique to extract quantitative information about water-rock interactions from rocks.

Reduced Genotoxicity of Gold Nanoparticles With Protein Corona in Allium cepa.

Increased usage of gold nanoparticles (AuNPs) in biomedicine, biosensing, diagnostics and cosmetics has undoubtedly facilitated accidental and unintentional release of AuNPs into specific microenvironments. This is raising serious questions concerning adverse effects of AuNPs on off-target cells, tissues and/or organisms. Applications utilizing AuNPs will typically expose the nanoparticles to biological fluids such as cell serum and/or culture media, resulting in the formation of protein corona (PC) on the AuNPs. Evidence for PC altering the toxicological signatures of AuNPs is well studied in animal systems. In this report, we observed significant genotoxicity in Allium cepa root meristematic cells (an off-target bioindicator) treated with high concentrations (≥100 µg/ml) of green-synthesized vanillin capped gold nanoparticles (VAuNPs). In contrast, protein-coated VAuNPs (PC-VAuNPs) of similar concentrations had negligible genotoxic effects. This could be attributed to the change in physicochemical characteristics due to surface functionalization of proteins on VAuNPs and/or differential bioaccumulation of gold ions in root cells. High elemental gold accumulation was evident from µ-XRF mapping in VAuNPs-treated roots compared to treatment with PC-VAuNPs. These data infer that the toxicological signatures of AuNPs are influenced by the biological route that they follow to reach off-target organisms such as plants. Hence, the current findings highlight the genotoxic risk associated with AuNPs, which, due to the enhanced utility, are emerging as new pollutants. As conflicting observations on the toxicity of green-synthesized AuNPs are increasingly reported, we recommend that detailed studies are required to investigate the changes in the toxicological signatures of AuNPs, particularly before and after their interaction with biological media and systems.

X-ray fluorescence mapping: Insights into mesoscale structure impact on battery functional electrochemistry

Electron transfer and ion transport occurs over multiple-length scales ranging from the atomic to mesoscale within battery materials and electrodes. Micro-X-ray fluorescence (µ-XRF) is an important characterization tool as it can resolve structural, compositional, and redox information while providing insight into the spatial distribution of an electroactive material. In this work, µ-XRF mapping is used to probe the distribution of iron within thin planar slurry-based and thick porous carbon nanotube (CNT)-based magnetite (Fe3O4) electrodes. Notably, the porous CNT-based electrode showed homogenous distribution of Fe within the electrode whereas the planar electrode demonstrated distinct Fe aggregates. This information was used to rationalize the electrochemistry observed by cyclic voltammetry and galvanostatic cycling. The thick porous electrode delivered 215% more capacity per gram of magnetite during the first discharge, consistent with increased electrode homogeneity enabling effective ion access and electron transfer.Graphical

Sphalerite weathering and controls on Zn and Cd migration in mine waste rock: An integrated study from the molecular scale to the field scale

Degraded water quality and environmental impacts caused by weathering of sulfide-bearing mine wastes are a legacy remaining at many historical mine sites. Release and mobilization of toxic metals (e.g., Zn and Cd) in mine drainage are often associated with weathering of primary sulfide minerals and precipitation and dissolution of secondary minerals. This study aims to couple field-scale measurements of physicochemical parameters with μm- and nm-scale mineralogical characterization to investigate sphalerite weathering and controls on Zn and Cd migration in an uncovered mine waste-rock pile. Elevated concentrations of Zn and Cd, potentially harmful to the receiving environment, were detected in waste-rock pore water and seepage. A suite of analytical techniques, including scanning electron microscopy – energy dispersive X-ray spectroscopy (SEM-EDS), scanning transmission electron microscopy (STEM) with EDS, electron microprobe analysis (EMPA), and synchrotron-based micro X-ray fluorescence (μ-XRF) mapping and micro X-ray absorption near edge structure (μ-XANES) spectroscopy were utilized in a high-resolution investigation of elemental- and secondary-mineral associations with sphalerite grains. EMPA and μ-XRF elemental maps and STEM investigations show depletion of Zn, Fe, S, and Cd, local enrichment of Cu, and distinct dissolution pits at the margins of sphalerite grains. Using μ-XANES, the speciation of solid phases containing Zn, Cu, Fe, and S indicates the dominance of primary sphalerite with microscopic inclusions of chalcopyrite, along with sparse occurrence of secondary Cu-bearing sulfides formed during weathering. These results suggest sphalerite oxidation leads to congruent dissolution without formation of distinct secondary-mineral coatings. Sphalerite weathering significantly contributes to elevated aqueous concentrations of Zn and Cd. Field-scale observations and mineralogical investigations indicate common occurrence of Fe-oxyhydroxides in the waste-rock pile. Seepage chemistry and surface complexation modeling results suggest that pH-dependent variations in reactions on the surfaces of the Fe-oxyhydroxides control aqueous concentrations of Zn and Cd, and the Zn/Cd ratio in the seepage. This work highlights the importance of understanding the mechanisms of sulfide-mineral oxidation and subsequent surface precipitation and adsorption, such that appropriate remediation action can be implemented to limit mobilization of metals to sensitive ecosystems.