Synchrotron-based X-ray Fluorescence Research Articles

Travelling in Microphis (Teleostei: Syngnathidae) Otoliths with Two-Dimensional X-ray Fluorescence Maps: Twists and Turns on the Road to Strontium Incorporation.

Indo-Pacific tropical island streams are home to freshwater pipefish (Microphis spp., Syngnathidae). Otoliths were used to uncover life history traits in four species, including a New Caledonian endemic. All four species present the same methodological challenge: their otoliths are small, fragile and mute for growth marks using basic observation tools. Strontium (Sr) is calcium substituent in the mineral lattice, driven by salinity conditions, and thus useful to study diadromous migrations. Synchrotron-based scanning X-ray fluorescence 2D high-resolution mapping allowed us to tackle the global and hyperfine strontium (Sr) distribution. We developed analytical imaging processes to retrieve biological information from otoliths from the data generated via synchrotron analysis. We uncovered plasticity in the life cycle: all species were amphidromous, apart from some freshwater residents from New Caledonia. Understanding life cycle modalities is crucial to categorize species distribution limits and to implement adapted conservation measures, especially when endemic species are at stake. 2D fine-scale images outlined the heterogeneity of Sr distribution: in addition to the trivial Sr incorporation driven by environmental ionic conditions, there is an unusual mosaic arrangement of Sr distribution and we hypothesize that biological control, especially growth during the early life stages, may sometimes overrule stoichiometry. This shows that it is worth studying otolith formation and element integration at imbricated scales, and our methods and results provide a strong basis for future works and prospects in otolith science.

High-Grade REE accumulation in regolith: Insights from supergene alteration of an apatite-rich vein at the Kapunda Cu mine, South Australia

AbstractThe stratiform and vein-hosted Kapunda Cu deposit in South Australia contains a saprolitized hydrothermal vein with 12.37 wt.% total rare earth oxide (TREO). The vein was analyzed by X-ray diffraction, scanning electron microscopy, synchrotron-based X-ray fluorescence microscopy and electron backscatter diffraction to understand the controls that govern high-grade REE accumulation during periods of intense weathering. Petrological assessments indicate the transformation of an apatite-calcite-aluminosilicate-bearing protolith to a supergene assemblage of Fe-oxides, kaolinite and REE-phosphate minerals that include rhabdophane-(Ce), monazite-(Ce) and florencite-(Ce). This transformation was facilitated by progressive acidification of the weathering fluid, which is indicated by: 1) the increasing crystallinity of authigenic Fe-oxides and kaolinite, which led to REE desorption; 2) the textural evolution and increase in grain size of authigenic REE-phosphates from nanoscopic crystallites, to acicular needles, to micro-scale hexagonal prisms; 3) the late dissolution of REE-phosphates; and 4) the replacement of goethite by jarosite, whose sulfate component originated from the oxidation and weathering of proximal sulfide minerals. Alongside the depletion of pH-buffering carbonate minerals that are indicated by the preservation of calcite menisci, this sulfide dissolution also facilitated acid generation. Results illustrate how highly acidic weathering fluids might facilitate either REE mobilization or REE accumulation in regolith. High-grade REE accumulation under acidic supergene conditions is prioritized when the host-rock contains a significant source of depositional ligands (i.e., phosphate in the form of apatite) that can be readily leached during intense weathering. Exploration companies should therefore assay routinely for REEs in any heavily weathered phosphatic rock, due to the observed efficiency of phosphate minerals as geochemical traps for REE accumulation.

Migration of transition metals and potential for carbon mineralization during acid leaching of processed kimberlite from Venetia diamond mine, South Africa

Carbonation of mafic and ultramafic rocks and mineral wastes provides a permanent way to sequester excess atmospheric CO2. Recent research has shown that this method also offers the potential for enhanced recovery of critical metals from mine tailings. In this study, processed kimberlite from the Venetia diamond mine (South Africa) was used in column acid leaching experiments to assess both its carbonation potential and whether critical metals such as nickel could be recovered during mineral carbonation. Processed kimberlite was treated daily with one pore volume of either deionized water or dilute hydrochloric acid (0.04 M, 0.08 M, 0.12 M and 0.16 M) for 28 days. Iron-rich yellow precipitates consistent with yellow ground formed during the experiments both at the top of the residue columns (corresponding to the inlets of the columns) and within the leachates collected from the bases of columns. The carbonation potential and mobility of transition metals were investigated using a combination of quantitative X-ray diffraction (XRD) using Rietveld refinements, inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDXS), transmission electron microscopy (TEM) coupled with EDXS, and synchrotron-based X-ray fluorescence microscopy (XFM). Our results show that the high proportion of clay minerals (e.g., lizardite, smectite, talc, chlorite) in the processed kimberlite act as the primary source for Mg and transition metals such as Ni; however, calcite dissolution is the main source for Ca. The amount of Mg and Ca extracted from processed kimberlite increases with HCl concentration. If acid leaching of processed kimberlite were used at Venetia, the amount of Mg leached from clay minerals would provide an estimated CO2 offset potential ranging from 2.1 to 15.8 % of the mine's total annual emissions. The leached Ca from silicate dissolution could also provide an estimated CO2 offset potential ranging from 2.1 to 8.1 % of the mine's total annual emissions. However, the amount of CO2 released by calcite dissolution during this process is equivalent to 2.1–14.3 % of total annual CO2 emissions at Venetia., thus resulting in a net estimated CO2 offset potential of 2.1–9.6 % if the Ca released from calcite could not be recarbonated. If all of the Ca could be reprecipitated as calcite, the acid leaching techniques employed in this study could offset 4.2–23.9 % of the Venetia mine's CO2 emissions. Ultimately, greater concentrations and/or amounts of acid may be used to access more of the offset potential of Mg phyllosilicates in kimberlite, but the CO2 released by calcite dissolution must also be won back by recarbonation.

Operando synchrotron-based X-ray study and intervention approaches of graphene-related-materials for investigating the performance and durability of HT-PEMFC

The application of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) addresses challenges in water management, fuel purity, and overheating under high current density. However, phosphoric acid (PA) migration hinders their development. This study uses synchrotron-based X-ray fluorescence spectroscopy to investigate PA and catalyst migration. Interventions with single-layer graphene and electrochemically exfoliated graphene oxide improve performance and durability. X-ray absorption spectroscopy provides insights into relevant mechanisms, advancing understanding of membrane electrode assembly preparation and the intricate influences of PA and catalyst migration on performance and durability in HT-PEMFCs.

Impact of coconut-fiber biochar on lead translocation, accumulation, and detoxification mechanisms in a soil–rice system under elevated lead stress

Biochar, an environmentally friendly material, was found to passivate lead (Pb) in contaminated soil effectively. This study utilized spectroscopic investigations and partial least squares path modeling (PLS-PM) analysis to examine the impact of coconut-fiber biochar (CFB) on the translocation, accumulation, and detoxification mechanisms of Pb in soil-rice systems. The results demonstrated a significant decrease (p < 0.05) in bioavailable Pb concentration in paddy soils with CFB amendment, as well as reduced Pb concentrations in rice roots, shoots, and brown rice. Synchrotron-based micro X-ray fluorescence analyses revealed that CFB application inhibited the migration of Pb to the rhizospheric soil region, leading to reduced Pb uptake by rice roots. Additionally, the CFB treatment decreased Pb concentrations in the cellular protoplasm of both roots and shoots, and enhanced the activity of antioxidant enzymes in rice plants, improving their Pb stress tolerance. PLS-PM analyses quantified the effects of CFB on the accumulation and detoxification pathways of Pb in the soil–rice system. Understanding how biochar influences the immobilization and detoxification of Pb in soil–rice systems could provide valuable insights for strategically using biochar to address hazardous elements in complex agricultural settings.

Mapping Phosphorus Availability in Soil at a Large Scale and High Resolution Using Novel Diffusive Gradients in Thin Films Designed for X-ray Fluorescence Microscopy.

A novel binding layer (BL) as part of the diffusive gradients in thin films (DGT) technique was developed for the two-dimensional visualization and quantification of labile phosphorus (P) in soils. This BL was designed for P detection by synchrotron-based X-ray fluorescence microscopy (XFM). It differs from the conventional DGT BL as the hydrogel is eliminated to overcome the issue that the fluorescent X-rays of P are detected mainly from shallow sample depths. Instead, the novel design is based on a polyimide film (Kapton) onto which finely powdered titanium dioxide-based P binding agent (Metsorb) was applied, resulting in superficial P binding only. The BL was successfully used for quantitative visualization of P diffusion from three conventional P fertilizers applied to two soils. On a selection of samples, XFM analysis was confirmed by quantitative laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The XFM method detected significant differences in labile P concentrations and P diffusion zone radii with the P fertilizer incubation, which were explained by soil and fertilizer properties. This development paves the way for fast XFM analysis of P on large DGT BLs to investigate in situ diffusion of labile P from fertilizers and to visualize large-scale P cycling processes at high spatial resolution.

Synchrotron-based x ray fluorescence ghost imaging.

X ray fluorescence ghost imaging (XRF-GI) was recently demonstrated for x ray lab sources. It has the potential to reduce the acquisition time and deposited dose by choosing their trade-off with a spatial resolution while alleviating the focusing constraints of the probing beam. Here, we demonstrate the realization of synchrotron-based XRF-GI: we present both an adapted experimental setup and its corresponding required computational technique to process the data. This extends the above-mentioned potential advantages of GI to synchrotron XRF imaging. In addition, it enables new strategies to improve resilience against drifts at all scales and the study of previously inaccessible samples, such as liquids.

Archeological wood conservation with selected organosilicon compounds studied by XFM and nanoindentation

Waterlogged wood conservation is a complex and challenging task. Detailed knowledge about the interactions between the applied chemicals and wood is necessary to ensure the effective and safe conservation of wooden artifacts. The present research aims to determine the mechanism of dimensional stabilization of archeological wood by organosilicon compounds using the combination of synchrotron-based X-ray fluorescence microscopy (XFM) and nanoindentation. Archeological oak wood was treated with methyltrimethoxysilane, (3-mercaptopropyl)trimethoxysilane, or 1,3-bis-[(diethylamino)-3-(propoxy)propan-2-ol]-1,1,3,3-tetramethyldisiloxane, which in previous studies were found to be more effective than other organosilicons in stabilizing wood dimensions. The XFM and nanoindentation results showed that all three organosilicons infiltrated wood cell walls and enhanced their mechanical properties. The XFM also showed that part of the chemicals filled some void spaces like cell lumina. Based on the results obtained here and in our previous research, it is determined that the mechanism of archeological wood dimensional stabilization by organosilicon treatment is complex and likely involves both filling cell lumina and infiltration into cell walls where organosilicons interact with wood polymers.

Differences and similarities in selenium biopathways in Astragalus, Neptunia (Fabaceae) and Stanleya (Brassicaceae) hyperaccumulators.

Selenium hyperaccumulator species are of primary interest for studying the evolution of hyperaccumulation and for use in biofortification because selenium is an essential element in human nutrition. In this study, we aimed to determine whether the distributions of selenium in the three most studied hyperaccumulating taxa (Astragalus bisulcatus, Stanleya pinnata and Neptunia amplexicaulis) are similar or contrasting, in order to infer the underlying physiological mechanisms. This study used synchrotron-based micro-X-ray fluorescence (µXRF) techniques to visualize the distribution of selenium and other elements in fresh hydrated plant tissues of A. racemosus, S. pinnata and N. amplexicaulis. Selenium distribution differed widely in the three species: in the leaves of A. racemosus and N. amplexicaulis selenium was mainly concentrated in the pulvini, whereas in S. pinnata it was primarilylocalized in the leaf margins. In the roots and stems of all three species, selenium was absent in xylem cells, whereas it was particularly concentrated in the pith rays of S. pinnata and in the phloem cells of A. racemosus and N. amplexicaulis. This study shows that Astragalus, Stanleya and Neptunia have different selenium-handling physiologies, with different mechanisms for translocation and storage of excess selenium. Important dissimilarities among the three analysed species suggest that selenium hyperaccumulation has probably evolved multiple times over under similar environmental pressures in the US and Australia.

Severity of Hepatocyte Damage and Prognosis in Cirrhotic Patients Correlate with Hepatocyte Magnesium Depletion.

We aimed to evaluate the magnesium content in human cirrhotic liver and its correlation with serum AST levels, expression of hepatocellular injury, and MELDNa prognostic score. In liver biopsies obtained at liver transplantation, we measured the magnesium content in liver tissue in 27 cirrhotic patients (CIRs) and 16 deceased donors with healthy liver (CTRLs) by atomic absorption spectrometry and within hepatocytes of 15 CIRs using synchrotron-based X-ray fluorescence microscopy. In 31 CIRs and 10 CTRLs, we evaluated the immunohistochemical expression in hepatocytes of the transient receptor potential melastatin 7 (TRPM7), a magnesium influx chanzyme also involved in inflammation. CIRs showed a lower hepatic magnesium content (117.2 (IQR 110.5-132.9) vs. 162.8 (IQR 155.9-169.8) μg/g; p < 0.001) and a higher percentage of TRPM7 positive hepatocytes (53.0 (IQR 36.8-62.0) vs. 20.7 (10.7-32.8)%; p < 0.001) than CTRLs. In CIRs, MELDNa and serum AST at transplant correlated: (a) inversely with the magnesium content both in liver tissue and hepatocytes; and (b) directly with the percentage of hepatocytes stained intensely for TRPM7. The latter also directly correlated with the worsening of MELDNa at transplant compared to waitlisting. Magnesium depletion and overexpression of its influx chanzyme TRPM7 in hepatocytes are associated with severity of hepatocyte injury and prognosis in cirrhosis. These data represent the pathophysiological basis for a possible beneficial effect of magnesium supplementation in cirrhotic patients.

B.1 Imaging metabolic changes in white matter following ischemic and hemorrhagic stroke onset in an animal model

Background: What matter (WM) is particularly sensitive to ischemia and WM changes are observed following onset of ischemic stroke as well as during expansion of the stroke lesion. To better correlate neurobehavioural and functional assessments in our models we have developed imaging methods to aid in the differentiation and quantification of WM injury. Methods: We employ 3 mouse models of stroke: photothrombotic, temporary middle cerebral artery occlusion, and intracerebral hemorrhage. Naïve controls and surgical shams (for each model) are also characterized. We use Fourier transform infrared (FTIR) imaging and synchrotron-based X-ray fluorescence microscopy (XFM) to visualize metabolites and elemental markers, respectively. These post-mortem imaging techniques are combined with conventional histology to confirm neuroanatomic features and cell types. Results: The metabolic profile of WM in naïve, sham, and stroke models has been characterized in C57BL/6 mice. The metabolic markers we identify are highly specific and enable the automated differentiation of WM from other tissues. Our methods have been re-tooled to identify degeneration and injury of WM regions. Conclusions: The combination of FTIR imaging and XFM afford the means to readily differentiate WM changes following stroke onset. Significant dysregulation can be observed before the core or penumbra of the stroke lesion reaches WM-containing regions.

Synchrotron-based X-ray fluorescence microscopy mapping the ionome of a toxic freshwater cyanobacterium

Harmful algal blooms (HABs) pose a major environmental concern across the globe. In abundance, cyanobacteria, or so-called green-blue algae can produce extremely dangerous cyanotoxins that harm humans and animals. This study focused on the mapping and distribution of intracellular macro-and micronutrients of the wide-spread freshwater cyanobacteria Microcystis aeruginosa (M. aeruginosa). Towards a better understanding of trace metal uptake and homeostasis throughout the cell cycle, we quantitatively mapped the spatial distribution of the elements P, K, Fe, Ca, Zn, Mn, and Cu across the ultrastructure of frozen-hydrated single cells using state-of-the-art X-ray nanofluorescence imaging at the Advanced Photon Source (APS) at Argonne National Laboratory. Bulk cellular nutrient and trace metal content correlated well with the total intracellular elemental content in individual cells obtained by quantitative synchrotron X-ray fluorescence measurements. Multi-dimensional mappings showed P and K atoms colocalized as discrete semicircular hotspots that were analyzed with respect to their stoichiometry. Elevated Cu and Ca concentrations were detected along division plane of cells. P and K were found to have similar spatial elemental distribution with about 65% and 69% of the total cellular P and K, respectively, located at the hotspots. The P and K colocalization were refined further using nanotomography, showing a K envelope surrounding the P core. Inorganic P and organic P compounds were specified using solution-state 31P nuclear magnetic resonance (NMR) spectroscopy from M. aeruginosa. Of the total extracted P determined by 31P NMR spectroscopy, 47% were found to be nucleotides while only 11% were polyphosphates. Multimodal X-ray imaging provides a better understanding of intracellular biochemical processes in cyanobacteria, helping us monitor and combat an emerging environmental threat.

Zn isotope signatures in soil Fe[sbnd]Mn nodules with karst high geochemical background

Zn isotope has the potential to be used as an environmental tracer, due to its role in fingerprinting specific sources and processes. However, few studies have focused on Zn isotope system in terrestrial ferromanganese (FeMn) nodules, which is important on understanding the behaviors of Zn in soils. In this study, we analyse the isotopic composition in soil FeMn nodules and surrounding materials from a typical karst region in Guangxi Province, southwestern China and use advanced synchrotron-based methods to characterize Zn speciation. The Zn isotope compositions of the FeMn nodules range from 0.09 to 0.66 ‰, with an average value of 0.24 ‰. Pb isotope fingerprinting reveals that the major material sources contributing to the FeMn nodules are the surrounding soil (δ66Zn: ~0.36 ‰) and partly weathered carbonate bedrock (δ66Zn: ~0.58 ‰), which contain heavier Zn isotopes than the nodules. Synchrotron-based X-ray fluorescence (μ-SXRF) shows that Zn is well correlated with both Fe and Mn. X-ray absorption near edge spectroscopy (XANES) measurements reveal that Zn is associated with both goethite and birnessite phases, with goethite-sorbed Zn accounting for ~76 % of the total Zn and birnessite-sorbed Zn accounting for ~24 %. By combining these new results, the isotopically light Zn in the FeMn nodules compared to their sources can be explained by equilibrium sorption of Zn on goethite and birnessite, during which light Zn is preferentially sorbed. Our study provides important new data on Zn isotope compositions in terrestrial soil FeMn nodules and constrains associated mechanisms, and have implications for using Zn isotopes as environmental tracers.

Unmasking pipefish otolith using synchrotron-based scanning X-ray fluorescence

Scientists use otoliths to trace fish life history, especially fish migrations. Otoliths incorporate signatures of individual growth and environmental use. For many species, distinct increment patterns in the otolith are difficult to discern; thus, questions remain about crucial life history information. To unravel the history of such species, we use synchrotron-based scanning X-ray fluorescence. It allows the mapping of elements on the entire otolith at a high spatial resolution. It gives access to precise fish migration history by tagging landmark signature for environmental transition and it also characterises localised growth processes at a mineral level. Freshwater pipefish, which are of conservation concern, have otoliths that are small and fragile. Growth increments are impossible to identify and count; therefore, there is a major lack of knowledge about their life history. We confirm for the first time, by mapping strontium that the two tropical pipefish species studied are diadromous (transition freshwater/marine/freshwater). Mapping of other elements uncovered the existence of different migratory routes during the marine phase. Another major breakthrough is that we can chemically count growth increments solely based on sulphur signal as it is implicated in biomineralization processes. This novel method circumvents reader bias issues and enables age estimation even for otoliths with seemingly untraceable increments. The high spatial resolution elemental mapping methods push back limits of studies on life traits or stock characterisation.

Vanadium Speciation in Ancient Shales Revealed through Synchrotron-Based X-ray Spectroscopy

Redox-sensitive trace elements, such as vanadium, are frequently used as paleoredox proxies to infer the redox status of ancient marine depositional environments. When applied to vanadium, this approach relies on an accurate understanding of vanadium geochemistry in marine sediments. This, in turn, requires the application of analytical techniques capable of providing reliable chemical information on vanadium host phases of vanadium and thus the ability to distinguish authigenic from detrital phases. The increasing availability of synchrotron-based X-ray spectroscopic techniques capable of providing chemical speciation information at both the bulk and micro-scale presents an opportunity to refine our understanding of vanadium geochemistry in ancient marine sediments. Here, we show the utility of synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy and scanning X-ray fluorescence microscopy (SXFM) for investigating vanadium host phases in ancient marine sediments. The studied samples from the 1400 Ma Xiamaling Formation came from strongly contrasting depositional settings (ranging from oxic to euxinic) with a wide range of vanadium enrichments (enrichment factors from 0.7 to 9.6), yet vanadium speciation determined by XANES was consistently found to be phyllosilicate-hosted vanadium (III). High-resolution elemental imaging by SXFM coupled with global statistical colocalization analyses revealed strong associations between vanadium and potassium, consistent with vanadium hosted by potassium-rich clay minerals. These findings, while demonstrating the power of synchrotron-based X-ray methods, imply that differentiating authigenic and detrital vanadium in ancient marine sediments is unlikely to be possible given that post-depositional processes result in similar chemical speciation for both fractions. This will also limit the reliability of vanadium isotope system studies that depend on differentiating authigenic and detrital fractions using selective extraction procedures.

Synchrotron XRF and Histological Analyses Identify Damage to Digestive Tract of Uranium NP-Exposed Daphnia magna.

Micro- and nanoscopic X-ray techniques were used to investigate the relationship between uranium (U) tissue distributions and adverse effects to the digestive tract of aquatic model organism Daphnia magna following uranium nanoparticle (UNP) exposure. X-ray absorption computed tomography measurements of intact daphnids exposed to sublethal concentrations of UNPs or a U reference solution (URef) showed adverse morphological changes to the midgut and the hepatic ceca. Histological analyses of exposed organisms revealed a high proportion of abnormal and irregularly shaped intestinal epithelial cells. Disruption of the hepatic ceca and midgut epithelial tissues implied digestive functions and intestinal barriers were compromised. Synchrotron-based micro X-ray fluorescence (XRF) elemental mapping identified U co-localized with morphological changes, with substantial accumulation of U in the lumen as well as in the epithelial tissues. Utilizing high-resolution nano-XRF, 400-1000 nm sized U particulates could be identified throughout the midgut and within hepatic ceca cells, coinciding with tissue damages. The results highlight disruption of intestinal function as an important mode of action of acute U toxicity in D. magna and that midgut epithelial cells as well as the hepatic ceca are key target organs.

Visualizing Metal Distribution in Plants Using Synchrotron X-Ray Fluorescence Microscopy Techniques.

Recent improvements in synchrotron-based X-ray fluorescence (SXRF) microscopy established it as an advanced analytical tool for analyzing 2D- and 3D distribution of mineral elements in plants. Among existing imaging techniques, SXRF microscopy offers several unique capabilities, including in situ metal quantification in plant tissues and high sensitivity, as low as 1mgkg-1, at the nanoscale spatial resolution. SXRF is increasingly utilized in different plant science disciplines to provide a fundamental understanding of metal homeostasis, and the function of trace elements in plant metabolism and development. Here, we describe methods for SXRF imaging, including sample preparation, the optimization of conventional SXRF for analyzing trace elements, and the development of confocal SXRF (C-SXRF).

Detention and mapping of iron and toxic environmental elements in human ovarian endometriosis: A suggested combined role

BackgroundEndometriosis is a disease affecting 10–15 % of women worldwide, consisting in the ectopic growth of endometrial cells outside the uterine cavity.Whist the pathogenetic mechanisms of endometriosis remain elusive and contemplating even environmental causes, iron deposits are common in endometrial lesions, indicating an altered iron metabolism at this level. This study was undertaken to reveal a possible relationship between iron dysmetabolism and accumulation of environmental metals. MethodsBy combining histological and histochemical analysis (H&E and Perl's staining) with μ- and nano- synchrotron-based (SR-based) X-ray Fluorescence (XRF) microscopy, we investigated the distribution of iron and other elements in the ovarian endometriomas of 12 endometriosis patients and in 7 healthy endometrium samples. ResultsXRF microscopy expanded the findings obtained by Perl's staining, revealing with an exceptional sensitivity intracellular features of iron accumulation in the epithelial endometrium, stroma and macrophages of the endometriotic lesions. XRF evidenced that iron was specifically accumulated in multiple micro aggregates, reaching concentrations up to 10–20 % p/p. Moreover, by XRF analysis we revealed for the first time the retention of a number of exogenous and potentially toxic metals such as Pb, Br, Ti, Al Cr, Si and Rb partially or totally co-localizing with iron. ConclusionμXRF reveals accumulation and colocalization of iron and environmental metals in human ovarian endometriosis, suggesting a role in the pathogenesis of endometriosis.

Dynamic development of geochemical reaction fronts during hydraulic stimulation of shale

Injection of acidic hydraulic fracture fluid (HFF) into shale formations for unconventional oil/gas production results in chemical reactions in the shale matrix that can alter fluid transport. Here, we report the results of set of experiments designed to evaluate the impact of calcite dissolution as a function of carbonate mineral content on matrix chemical reactivity and pore-space modification concomitant with imbibition. We tracked acidic HFF transport in four samples of Wolfcamp shale with calcite contents varying from 4% to 59% by monitoring the rate and spatial extent of bromide tracer transport using synchrotron-based X-ray fluorescence microprobe (XFM) imaging. Concurrently, we also carried out XFM imaging of the spatial distribution of Ca in the Wolfcamp shale cores (as a proxy of calcite distribution). Our approach thus yields a direct record of time-resolved selective ion transport resulting from the penetration of acidic HFF and the associated mineral transformations in the shale cores.We show that the variability in calcite content of Wolfcamp shale samples can directly affect the rate and spatial extent of imbibition. Although reaction of the acidic HFF with carbonates in shales enhances calcite dissolution and increases porosity, the spatial extent of calcite dissolution in the shale matrix is limited due to a rapid neutralization of pH. The relative abundance and spatial distribution of calcite control the chemical saturation state of the HFF progressing into the matrix. As a result, calcite has a major impact on the spatial extent and rate of matrix alteration and thus on HFF transport during subsurface reservoir stimulation. Consequently, increased calcite content in the shale matrix inhibits the spatial extent of the pore-volume increase and, by extension, the spatial extent and rate of imbibition.Our results thus show that the overall rates of calcite dissolution approach the rates of acidic HFF transport (i.e., Damköhler number ∼1), which could contribute to the efficiency of subsurface reservoir stimulation. A better understanding of HFF-calcite reaction rates is crucial for improving the prediction and optimization of fluid transport across HFF-shale interfaces during hydraulic fracturing.

Microbially influenced tungsten mobilization and formation of secondary minerals in wolframite tailings

Wolframite [(Fe,Mn)WO4] tailings represent a hazardous waste that can pose a threat to the environment, humans, animals and plants. The present study aims to conduct a high-resolution depth profile characterization of wolframite tailings from Wolfram Camp, North Queensland, Australia, to understand the biogeochemical influences on W mobilization. Several indigenous Fe- and S-oxidizing bacteria (e.g., Streptococcus pneumoniae and Thiomonas delicata) in wolframite tailings were found highly associated with W, As, and rare earth elements. Biooxidation of metal sulfides, i.e., pyrite, molybdenite and bismuthinite, produced sulfuric acid, which accelerated the weathering of wolframite, mobilizing tungstate (WO42-). Using synchrotron-based X-ray fluorescence microscopy (XFM) and W L-edge X-ray absorption near-edge spectroscopy (µ-XANES) analysis, wolframite was initially transformed into Na- and Bi- tungstate as well as tungstic acid (partial weathering) followed by the formation of Ga- and Zn- tungstate after extensive weathering, i.e., the wolframite had disappeared. While W (VI) was the major W species in wolframite tailings, minor W(0) and W(II), and trace W(IV) were also detected. The major contaminant in the Wolfram Camp tailings was As. Though wolframite tailings are hazardous waste, the toxicity of W was unclear. Tungsten waste still has industrial value; apart from using them as substitution material for cement and glass production, there is interest in reprocessing W waste for valuable metal recovery. If the environmental benefits are taken into consideration, i.e., preventing the release of toxic metals into surrounding waterways, reprocessing may be economic.