Sea-level rise and arsenic-rich soils: A toxic relationship

In the United States, dangerously high arsenic (As) levels have been found in drinking water wells in more than 25 states, potentially exposing 2.1 million people to drinking water high in As; a known carcinogen. The anticipated sea-level rise (SLR) is expected to alter soil biogeochemical and hydrological conditions, potentially impacting their ability to sequester As. In our study of coastal Wilmington, DE, an area projected to experience a 1 -meter SLR by 2100, we examined the spatial distribution, speciation, and release possibilities of As due to SLR. To understand the complex dynamics at play, we employed a comprehensive approach, including bulk and micro X-ray absorption spectroscopy measurements, hydrological pattern evaluation, and macroscopic stirred-flow experiments. Our results suggest that introducing reducing and saline conditions can increase As release in both river water and seawater inundation scenarios, most likely due to ionic competition and the dissolution of As-bearing Fe/Mn oxides. Regardless of the salinity source, the released As concentrations consistently exceeded the EPA threshold for drinking water. Our results provide valuable insights for developing appropriate remedial and management strategies for this site and numerous others facing similar environmental challenges. ENVIRONMENTAL IMPLICATION: With nearly two hundred million individuals living within coastal flood plains and with two million square kilometers of land and one trillion dollars' worth of assets lying less than 1 m above current sea level, sea-level rise (SLR) is one of the significant socio-economic threats associated with global warming. Arsenic is a prevalent contaminant in coastal areas impacted by industrial activities, many of which are susceptible to being impacted by SLR. This study examines SLR's impact on arsenic fate and speciation in a densely populated coastline in Wilmington, DE, expecting 1 meter of SLR by 2100.

Ectomycorrhizal fungi enhance pine growth by stimulating iron-dependent mechanisms with trade-offs in symbiotic performance

Iron (Fe) is crucial for metabolic functions of living organisms. Plants access occluded Fe through interactions with rhizosphere microorganisms and symbionts. Yet, the interplay between Fe addition and plant-mycorrhizal interactions, especially the molecular mechanisms underlying mycorrhiza-assisted Fe processing in plants, remains largely unexplored. We conducted mesocosms in Pinus plants inoculated with different ectomycorrhizal fungi (EMF) Suillus species under conditions with and without Fe coatings. Meta-transcriptomic, biogeochemical, and X-ray fluorescence imaging analyses were applied to investigate early-stage mycorrhizal roots. While Fe addition promoted Pinus growth, it concurrently reduced mycorrhiza formation rate, symbiosis-related metabolites in plant roots, and aboveground plant carbon and macronutrient content. This suggested potential trade-offs between Fe-enhanced plant growth and symbiotic performance. However, the extent of this trade-off may depend on interactions between host plants and EMF species. Interestingly, dual EMF species were more effective at facilitating plant Fe uptake by inducing diverse Fe-related functions than single-EMF species. This subsequently triggered various Fe-dependent physiological and biochemical processes in Pinus roots, significantly contributing to Pinus growth. However, this resulted in a greater carbon allocation to roots, relatively reducing the aboveground plant carbon content. Our study offers critical insights into how EMF communities rebalance benefits of Fe-induced effects on symbiotic partners.

Sequential removal of cation/H+ exchangers reveals their additive role in elemental distribution, calcium depletion and anoxia tolerance

Multiple Arabidopsis H+ /Cation exchangers (CAXs) participate in high-capacity transport into the vacuole. Previous studies have analysed single and double mutants that marginally reduced transport; however, assessing phenotypes caused by transport loss has proven enigmatic. Here, we generated quadruple mutants (cax1-4: qKO) that exhibited growth inhibition, an 85% reduction in tonoplast-localised H+ /Ca transport, and enhanced tolerance to anoxic conditions compared to CAX1 mutants. Leveraging inductively coupled plasma mass spectrometry (ICP-MS) and synchrotron X-ray fluorescence (SXRF), we demonstrate CAX transporters work together to regulate leaf elemental content: ICP-MS analysis showed that the elemental concentrations in leaves strongly correlated with the number of CAX mutations; SXRF imaging showed changes in element partitioning not present in single CAX mutants and qKO had a 40% reduction in calcium (Ca) abundance. Reduced endogenous Ca may promote anoxia tolerance; wild-type plants grown in Ca-limited conditions were anoxia tolerant. Sequential reduction of CAXs increased mRNA expression and protein abundance changes associated with reactive oxygen species and stress signalling pathways. Multiple CAXs participate in postanoxia recovery as their concerted removal heightened changes in postanoxia Ca signalling. This work showcases the integrated and diverse function of H+ /Cation transporters and demonstrates the ability to improve anoxia tolerance through diminishing endogenous Ca levels.

Chromium speciation and mobility in contaminated coastal urban soils affected by water salinity and redox conditions

Chromium (Cr) is a redox-sensitive element in contaminated coastal urban soils. Sea level rise (SLR) with subsequent soil inundation may facilitate Cr transformation and mobilization through alterations in local redox conditions and porewater ion composition. We investigated the impact of water salinity and redox conditions on Cr chemistry in these environments. Synchrotron-based X-ray spectroscopy and wet chemical analyses revealed that the soils contained very high levels of Cr (up to 4320 mg kg-1) and that chromite (∼52%) and Fe-Cr hydroxide coprecipitates (∼44%) were the predominant Cr species. The abundance of these two components resulted in low Cr mobility under non-flooded conditions. Chromium(II) was identified in the soils, potentially derived from the waste parent material. Seawater and anoxic conditions resulted in lower Cr release compared to freshwater and aerobic conditions. Up to three to eight times more Cr was released under aerobic conditions versus anaerobic conditions in the freshwater versus saltwater, respectively, with total dissolved Cr values remaining below 0.02 mg L-1. The decrease in Cr release was likely due to Cr reduction by Fe(II) and sulfide. This work provides important information on how salinity and redox fluctuations impact Cr cycling which is likely to occur during SLR.

Loss of OPT3 function decreases phloem copper levels and impairs crosstalk between copper and iron homeostasis and shoot-to-root signaling in Arabidopsis thaliana

Copper (Cu) and iron (Fe) are essential micronutrients that are toxic when accumulating in excess in cells. Thus, their uptake by roots is tightly regulated. While plants sense and respond to local Cu availability, the systemic regulation of Cu uptake has not been documented in contrast to local and systemic control of Fe uptake. Fe abundance in the phloem has been suggested to act systemically, regulating the expression of Fe uptake genes in roots. Consistently, shoot-to-root Fe signaling is disrupted in Arabidopsis thaliana mutants lacking the phloem companion cell-localized Fe transporter, OLIGOPEPTIDE TRANSPORTER 3 (AtOPT3). We report that AtOPT3 also transports Cu in heterologous systems and contributes to its delivery from sources to sinks in planta. The opt3 mutant contained less Cu in the phloem, was sensitive to Cu deficiency and mounted a transcriptional Cu deficiency response in roots and young leaves. Feeding the opt3 mutant and Cu- or Fe-deficient wild-type seedlings with Cu or Fe via the phloem in leaves downregulated the expression of both Cu- and Fe-deficiency marker genes in roots. These data suggest the existence of shoot-to-root Cu signaling, highlight the complexity of Cu/Fe interactions, and the role of AtOPT3 in fine-tuning root transcriptional responses to the plant Cu and Fe needs.

Multimodal X-ray nano-spectromicroscopy analysis of chemically heterogeneous systems

Understanding the nanoscale chemical speciation of heterogeneous systems in their native environment is critical for several disciplines such as life and environmental sciences, biogeochemistry, and materials science. Synchrotron-based X-ray spectromicroscopy tools are widely used to understand the chemistry and morphology of complex material systems owing to their high penetration depth and sensitivity. The multidimensional (4D+) structure of spectromicroscopy data poses visualization and data-reduction challenges. This paper reports the strategies for the visualization and analysis of spectromicroscopy data. We created a new graphical user interface and data analysis platform named XMIDAS (X-ray multimodal image data analysis software) to visualize spectromicroscopy data from both image and spectrum representations. The interactive data analysis toolkit combined conventional analysis methods with well-established machine learning classification algorithms (e.g. nonnegative matrix factorization) for data reduction. The data visualization and analysis methodologies were then defined and optimized using a model particle aggregate with known chemical composition. Nanoprobe-based X-ray fluorescence (nano-XRF) and X-ray absorption near edge structure (nano-XANES) spectromicroscopy techniques were used to probe elemental and chemical state information of the aggregate sample. We illustrated the complete chemical speciation methodology of the model particle by using XMIDAS. Next, we demonstrated the application of this approach in detecting and characterizing nanoparticles associated with alveolar macrophages. Our multimodal approach combining nano-XRF, nano-XANES, and differential phase-contrast imaging efficiently visualizes the chemistry of localized nanostructure with the morphology. We believe that the optimized data-reduction strategies and tool development will facilitate the analysis of complex biological and environmental samples using X-ray spectromicroscopy techniques.

A low-input strategy for chromium removal from industrial stormwater using peat sorbent

Low-cost and low-input water treatment systems are important for industrial stormwater remediation. Here we examine a flow-through reactor treatment installation where water exceeds the allowable maximum concentration for drinking water in multiple metals (e.g., chromium [Cr], cadmium [Cd], zinc [Zn]) prior to treatment. Specifically, we seek to understand why Cr attenuated in the reactors is not leachable by identifying the specific chemical form of Cr and dominant mechanisms promoting sequestration in the reactors. Total solid-phase Cr concentration in the peat media ranged from 50 to 150 mg/kg after 1 yr of exposure to stormwater to 300 to 900 mg/kg after 3.5 yr. X-ray fluorescence mapping images show Cr, iron (Fe), and Zn spatially correlated over a scale of 10 μm to 5 mm. Chromium rinds form on the edges of peat particles as Cr accumulates. Chromium and Fe K-edge X-ray absorption near edge structure spectroscopy reveal chromium predominately in the 3+ oxidation state with lesser amounts of elemental Cr. We propose the primary means of chromium attenuation in the reactors is precipitation as Cr-Fe hydroxides combined with trivalent Cr adsorption onto peat surfaces.

Sugar loading is not required for phloem sap flow in maize plants

Phloem transport of photoassimilates from leaves to non-photosynthetic organs, such as the root and shoot apices and reproductive organs, is crucial to plant growth and yield. For nearly 90 years, evidence has been generally consistent with the theory of a pressure-flow mechanism of phloem transport. Central to this hypothesis is the loading of osmolytes, principally sugars, into the phloem to generate the osmotic pressure that propels bulk flow. Here we used genetic and light manipulations to test whether sugar import into the phloem is required as the driving force for phloem sap flow. Using carbon-11 radiotracer, we show that a maize sucrose transporter1 (sut1) loss-of-function mutant has severely reduced export of carbon from photosynthetic leaves (only ~4% of the wild type level). Yet, the mutant remarkably maintains phloem pressure at ~100% and sap flow speeds at ~50-75% of those of wild type. Potassium (K⁺) abundance in the phloem was elevated in sut1 mutant leaves. Fluid dynamic modelling supports the conclusion that increased K⁺ loading compensated for decreased sucrose loading to maintain phloem pressure, and thereby maintained phloem transport via the pressure-flow mechanism. Furthermore, these results suggest that sap flow and transport of other phloem-mobile nutrients and signalling molecules could be regulated independently of sugar loading into the phloem, potentially influencing carbon-nutrient homoeostasis and the distribution of signalling molecules in plants encountering different environmental conditions.

Structural and Valence State Modification of Cobalt in CoPt Nanocatalysts in Redox Conditions

Platinum is the primary catalyst for many chemical reactions in the field of heterogeneous catalysis. However, platinum is both expensive and rare. Therefore, it is advantageous to combine Pt with another metal to reduce cost while also enhancing stability. To that end, Pt is often combined with Co to form Co-Pt nanocrystals. However, dynamical restructuring effects that occur during reaction in Co-Pt ensembles can impact catalytic properties. In this study, model Co₂Pt₃ nanoparticles supported on carbon were characterized during a redox cycle with two in situ approaches, namely, X-ray absorption spectroscopy (XAS) and scanning transmission electron microscopy (STEM) using a multimodal microreactor. The sample was exposed to temperatures up to 500 °C under H₂, and then to O₂ at 300 °C. Irreversible segregation of Co in the Co₂Pt₃ particles was seen during redox cycling, and substantial changes of the oxidation state of Co were observed. After H₂ treatment, a fraction of Co could not be fully reduced and incorporated into a mixed Co-Pt phase. Reoxidation of the sample increased Co segregation, and the segregated material had a different valence state than in the fresh, oxidized sample. This in situ study describes dynamical restructuring effects in CoPt nanocatalysts at the atomic scale that are crucial to understand in order to improve the design of catalysts used in major chemical processes.

Disentangling the role of ectomycorrhizal fungi in plant nutrient acquisition along a Zn gradient using X-ray imaging

Zinc (Zn) is a plant essential micronutrient involved in a wide range of cellular processes. Ectomycorrhizal fungi (EMF) are known to play a critical role in regulating plant Zn status. However, how EMF control uptake and translocation of Zn and other nutrients in plant roots under different Zn conditions is not well known. Using X-ray fluorescence imaging, we found the EMF species Suillus luteus increased pine root Zn acquisition under low Zn concentrations and reduced its accumulation under higher Zn levels. By contrast, non-mycorrhizal pine roots exposed to high Zn indiscriminately take up and translocate Zn to root tissues, leading to Zn stress. Regardless of S. luteus inoculation, the absorption pattern of Ca and Cu was similar to Zn. Compared to Ca and Cu, effects of S. luteus on Fe acquisition were more marked, leading to a negative association between Zn addition and Fe concentration within EMF roots. Besides, higher nutrient accumulation in the fungal sheath, compared to hyphae inhabiting between intercellular space of cortex cells, implies the fungal sheath serves as a barrier to regulate nutrient transportation into fungal Hartig net. Our results demonstrate the crucial roles EMF play in plant nutrient uptake and how fungal partners ameliorate soil chemical conditions either by increasing or decreasing element uptake.

Redundant roles of four ZIP family members in zinc homeostasis and seed development in Arabidopsis thaliana

Zinc (Zn) is essential for normal plant growth and development. The Zn-regulated transporter, iron-regulated transporter (IRT)-like protein (ZIP) family members are involved in Zn transport and cellular Zn homeostasis throughout the domains of life. In this study, we have characterized four ZIP transporters from Arabidopsis thaliana (IRT3, ZIP4, ZIP6, and ZIP9) to better understand their functional roles. The four ZIP proteins can restore the growth defect of a yeast Zn uptake mutant and are upregulated under Zn deficiency. Single and double mutants show no phenotypes under Zn-sufficient or Zn-limited growth conditions. In contrast, triple and quadruple mutants show impaired growth irrespective of external Zn supply due to reduced Zn translocation from root to shoot. All four ZIP genes are highly expressed during seed development, and siliques from all single and higher-order mutants exhibited an increased number of abnormal seeds and decreased Zn levels in mature seeds relative to wild type. The seed phenotypes could be reversed by supplementing the soil with Zn. Our data demonstrate that IRT3, ZIP4, ZIP6, and ZIP9 function redundantly in maintaining Zn homeostasis and seed development in A. thaliana.

Chemical state mapping of simulant Chernobyl lava-like fuel containing material using micro-focused synchrotron X-ray spectroscopy

Uranium speciation and redox behaviour is of critical importance in the nuclear fuel cycle. X-ray absorption near-edge spectroscopy (XANES) is commonly used to probe the oxidation state and speciation of uranium, and other elements, at the macroscopic and microscopic scale, within nuclear materials. Two-dimensional (2D) speciation maps, derived from microfocus X-ray fluorescence and XANES data, provide essential information on the spatial variation and gradients of the oxidation state of redox active elements such as uranium. In the present work, we elaborate and evaluate approaches to the construction of 2D speciation maps, in an effort to maximize sensitivity to the U oxidation state at the U L₃-edge, applied to a suite of synthetic Chernobyl lava specimens. Our analysis shows that calibration of speciation maps can be improved by determination of the normalized X-ray absorption at excitation energies selected to maximize oxidation state contrast. The maps are calibrated to the normalized absorption of U L₃ XANES spectra of relevant reference compounds, modelled using a combination of arctangent and pseudo-Voigt functions (to represent the photoelectric absorption and multiple-scattering contributions). We validate this approach by microfocus X-ray diffraction and XANES analysis of points of interest, which afford average U oxidation states in excellent agreement with those estimated from the chemical state maps. This simple and easy-to-implement approach is general and transferrable, and will assist in the future analysis of real lava-like fuel-containing materials to understand their environmental degradation, which is a source of radioactive dust production within the Chernobyl shelter.

Characterization of Materials Used as Face Coverings for Respiratory Protection

Use of masks is a primary tool to prevent the spread of the novel COVID-19 virus resulting from unintentional close contact with infected individuals. However, detailed characterization of the chemical properties and physical structure of common mask materials is lacking in the current literature. In this study, a series of commercial masks and potential mask materials, including 3M Particulate Respirator 8210 N95, a material provided by Oak Ridge National Laboratory Carbon Fiber Technology Facility (ORNL/CFTF), and a Filti Face Mask Material, were characterized by a suite of techniques, including scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. Wetting properties of the mask materials were quantified by measurements of contact angle with a saliva substitute. Mask pass-through experiments were performed using a dispersed metal oxide nanoparticle suspension to model the SARS-CoV-2 virus, with quantification via spatially resolved X-ray fluorescence mapping. Notably, all mask materials tested provided a strong barrier against respiratory droplet breakthrough. The comparisons and characterizations provided in this study provide useful information when evaluating mask materials for respiratory protection.

Imaging Zn and Ni distributions in leaves of different ages of the hyperaccumulator Noccaea caerulescens by synchrotron-based X-ray fluorescence

Mapping of leaves of hyperaccumulators can provide insights into the mechanisms these species utilize to accumulate high metal concentrations. We used synchrotron-based X-ray fluorescence (SXRF) to perform Zn and Ni imaging in leaves of different ages of Noccaea caerulescens. A mature leaf of the related non-hyperaccumulator Thlaspi arvense was also imaged. The concentrations of Zn, Ni, Co, and Cr in N. caerulescens grown on an ultramafic soil were 9-, 10-, 12-, and 3-fold higher than T. arvense. N. caerulescens showed an exceptional ability to accumulate Zn from the soil, posing a bioconcentration factor of 6.7. T. arvense had Zn and Ni distributed uniformly in the leaf blade with doubling fluorescence counts in the tip and margins, suggesting a strategy to excrete metals and avoid toxicity. On the other hand, N. caerulescens displayed distinctly different Zn and Ni accumulation patterns, regardless of the age or metal concentration in the leaves. Zinc was mainly distributed in the cells surrounding the central and secondary veins. Nickel accumulated in the margins and tips of the leaf blade. Given the time required to image large leaves in synchrotron facilities, small leaves can be used to represent the leaf distribution of Zn and Ni in N. caerulescens.

A Method to Preserve Wetland Roots and Rhizospheres for Elemental Imaging

Roots extensively interact with their soil environment but visualizing such interactions between roots and the surrounding rhizosphere is challenging. The rhizosphere chemistry of wetland plants is particularly challenging to capture because of steep oxygen gradients from the roots to the bulk soil. Here a protocol is described that effectively preserves root structure and rhizosphere chemistry of wetland plants through slam-freezing and freeze drying. Slam-freezing, where the sample is frozen between copper blocks pre-cooled with liquid nitrogen, minimizes root damage and sample distortion that can occur with flash-freezing while still minimizing chemical speciation changes. While sample distortion is still possible, the ability to obtain multiple samples quickly and with minimal cost increases the potential to obtain satisfactory samples and optimizes imaging time. The data show that this method is successful in preserving reduced arsenic species in rice roots and rhizospheres associated with iron plaques. This method can be adopted for studies of plant-soil relationships in a wide variety of wetland environments that span concentration ranges from trace-element cycling to phytoremediation applications.

Origin of tungsten and geochemical controls on its occurrence and mobilization in shallow sediments from Fallon, Nevada, USA

Tungsten (W) occurrence and speciation was investigated in sediments collected from Fallon, Nevada where previous studies have linked elevated W levels in human body fluids to an unusual cluster of childhood leukemia cases. The speciation of sedimentary W was determined by μ-XRF mapping and μ-XANES. The W content of the analyzed surface sediments ranged between 81 and 25,908 mg/kg, which is significantly higher than the W content in deeper sediments which ranged from 37 to 373 mg/kg at 30 cm depth. The μ-XANES findings reveal that approximately 20-50% of the total W in the shallow sediment occurs in the metallic form (W⁰); the rest occurs in the oxide form (W^VIO₃). Because W⁰ does not occur naturally, its elevated concentrations in surface sediments point toward a possible local anthropogenic origin. The oxidation of metallic W⁰ with meteoric waters likely leads to the formation of W^VIO₃. The chief water-soluble W species was identified as WO₄^2- by chromatographic separation and speciation modeling. These results led us to postulate that W⁰ particles from a currently unknown but local source(s) is (are) deposited onto the soils and/or surface sediments. The W⁰ in interaction with meteoric water is oxidized to W^VIO₃, and as these sediment-water interactions progress, WO₄^2- is formed in the water at pH ∼7. Under pH < 7, and sufficient W concentrations, tungstate tends to polymerize, and polymerized species are less likely to adsorb onto sediments. Polymerized species have lower affinity than monomers, which leads to enhanced mobility of W.

Effects of exogenous citric acid on the concentration and spatial distribution of Ni, Zn, Co, Cr, Mn and Fe in leaves of Noccaea caerulescens grown on a serpentine soil

The aim of this study was to show the potential of citric acid in increasing the concentration of Ni, Zn, Co, Cr, Mn and Fe in leaves of the hyperaccumulator Noccaea caerulescens. Synchrotron x-ray fluorescence (μ-XRF) images were collected to assess the distribution of metals in leaves. Applying citric acid (20 mmol kg^-1) to soil increased in 14-, 10-, 7-, 2- and 1.4- fold the concentration of Mn, Fe, Co, Ni, and Cr, respectively, compared to the control. The μ-XRF imaging revealed that Ni and Zn were not spatially correlated across the leaf. We observed a clear partitioning of Zn between veins and surrounding leaf cells while Ni was more evenly distributed between veins and leaf blade. The accumulation of metals in citric acid treated plants did not change the Ni and Zn distribution pattern in leaves but altered the Mn distribution. It seems that Mn reached toxic concentrations in leaves and we hypothesize that a mechanism driven by transpiration through the xylem was used to excrete the metal. Our results show that citric acid can enhance metal accumulation by N. caerulescens and have impact for soil remediation by either decreasing the time for clean up or increasing the access to non-labile pools of metals in soil.

A coded aperture microscope for X-ray fluorescence full-field imaging

The design and construction of an instrument for full-field imaging of the X-ray fluorescence emitted by a fully illuminated sample are presented. The aim is to produce an X-ray microscope with a few micrometers spatial resolution, which does not need to scan the sample. Since the fluorescence from a spatially inhomogeneous sample may contain many fluorescence lines, the optic which will provide the magnification of the emissions must be achromatic, i.e. its optical properties must be energy-independent. The only optics which fulfill this requirement in the X-ray regime are mirrors and pinholes. The throughput of a simple pinhole is very low, so the concept of coded apertures is an attractive extension which improves the throughput by having many pinholes, and retains the achromatic property. Modified uniformly redundant arrays (MURAs) with 10 µm openings and 50% open area have been fabricated using gold in a lithographic technique, fabricated on a 1 µm-thick silicon nitride membrane. The gold is 25 µm thick, offering good contrast up to 20 keV. The silicon nitride is transparent down into the soft X-ray region. MURAs with various orders, from 19 up to 73, as well as their respective negative (a mask where open and closed positions are inversed compared with the original mask), have been made. Having both signs of mask will reduce near-field artifacts and make it possible to correct for any lack of contrast.

High-sensitivity nanoscale chemical imaging with hard x-ray nano-XANES

Resolving chemical species at the nanoscale is of paramount importance to many scientific and technological developments across a broad spectrum of disciplines. Hard x-rays with excellent penetration power and high chemical sensitivity are suitable for speciation of heterogeneous (thick) materials. Here, we report nanoscale chemical speciation by combining scanning nanoprobe and fluorescence-yield x-ray absorption near-edge structure (nano-XANES). First, the resolving power of nano-XANES was demonstrated by mapping Fe(0) and Fe(III) states of a reference sample composed of stainless steel and hematite nanoparticles with 50-nm scanning steps. Nano-XANES was then used to study the trace secondary phases in lithium iron phosphate (LFP) particles. We observed individual Fe-phosphide nanoparticles in pristine LFP, whereas partially (de)lithiated particles showed Fe-phosphide nanonetworks. These findings shed light on the contradictory reports on Fe-phosphide morphology in the literature. Nano-XANES bridges the capability gap of spectromicroscopy methods and provides exciting research opportunities across multiple disciplines.

Defense Priming in Nicotiana tabacum Accelerates and Amplifies 'New' C/N Fluxes in Key Amino Acid Biosynthetic Pathways

In the struggle to survive herbivory by leaf-feeding insects, plants employ multiple strategies to defend themselves. One mechanism by which plants increase resistance is by intensifying their responsiveness in the production of certain defense agents to create a rapid response. Known as defense priming, this action can accelerate and amplify responses of metabolic pathways, providing plants with long-lasting resistance, especially when faced with waves of attack. In the work presented, short-lived radiotracers of carbon administered as 11CO2 and nitrogen administered as 13NH3 were applied in Nicotiana tabacum, to examine the temporal changes in 'new' C/N utilization in the biosynthesis of key amino acids (AAs). Responses were induced by using topical application of the defense hormone jasmonic acid (JA). After a single treatment, metabolic partitioning of recently fixed carbon (designated 'new' carbon and reflected as 11C) increased through the shikimate pathway, giving rise to tyrosine, phenylalanine and tryptophan. Amplification in 'new' carbon fluxes preceded changes in the endogenous (12C) pools of these AAs. Testing after serial JA treatments revealed that fluxes of 'new' carbon were accelerated, amplified and sustained over time at this higher rate, suggesting a priming effect. Similar results were observed with recently assimilated nitrogen (designated 'new' nitrogen reflected as 13N) with its partitioning into serine, glycine and glutamine, which play important roles supporting the shikimate pathway and downstream secondary metabolism. Finally, X-ray fluorescence imaging revealed that levels of the element Mn, an important co-factor for enzyme regulation in the shikimate pathway, increased within JA treated tissues, suggesting a link between plant metal ion regulation and C/N metabolic priming.

Citric acid-assisted accumulation of Ni and other metals by Odontarrhena muralis: Implications for phytoextraction and metal foliar distribution assessed by μ-SXRF

Odontarrhena muralis is one of the most promissing plant species for Ni phytomining, and soil amendments can further increase its Ni phytoextraction ability. Here we investigated whether Ni phytomining/phytoremediation using this Ni hyperaccumulator can benefit from applying citric acid to a serpentine soil that is naturally enriched in Ni (>1000 mg kg^-1). Synchrotron micro X-ray fluorescence (μ-SXRF) was used to image Ni and other metal distributions in whole fresh leaves of O. muralis. Leaf Ni accumulation in plants grown on citric acid-amended soil increased up to 55% while Co, Cr, Fe, Mn, and Zn concentrations were 4-, 14-, 6-, 7- and 1.3-fold higher than the control treatment. O. muralis presented high bioconcentration factors (leaf to soil concentration ratio) to Ni and Zn whereas Cr was seemingly excluded from uptake. The μ-SXRF images showed a uniform distribution of Ni, preferential localization of Co in the leaf tip, and clear concentration of Mn in the base of trichomes. The citric acid treatments strongly increased the Co fluoerescence intensity in the leaf tip and altered the spatial distribution of Mn across the leaf, but there was no difference in Ni fluorescence counts between the trichome-base region and the bulk leaf. Our data from a serpentine soil suggests that citrate treatment enhances Ni uptake, but Co is excreted from leaves even in low leaf concentrations, which can make Co phytoming using O. muralis unfeasible in natural serpentine soils.

A Pressure-Induced Inverse Order-Disorder Transition in Double Perovskites

Given the consensus that pressure improves cation ordering in most of known materials, a discovery of pressure-induced disordering could require recognition of an order-disorder transition in solid-state physics/chemistry and geophysics. Double perovskites Y₂ CoIrO₆ and Y₂ CoRuO₆ polymorphs synthesized at 0, 6, and 15 GPa show B-site ordering, partial ordering, and disordering, respectively, accompanied by lattice compression and crystal structure alteration from monoclinic to orthorhombic symmetry. Correspondingly, the long-range ferrimagnetic ordering in the B-site ordered samples are gradually overwhelmed by B-site disorder. Theoretical calculations suggest that unusual unit-cell compressions under external pressures unexpectedly stabilize the disordered phases of Y₂ CoIrO₆ and Y₂ CoRuO₆ .

Sea Level Rise Induced Arsenic Release from Historically Contaminated Coastal Soils

Climate change-induced perturbations in the hydrologic regime are expected to impact biogeochemical processes, including contaminant mobility and cycling. Elevated levels of geogenic and anthropogenic arsenic are found along many coasts around the world, most notably in south and southeast Asia but also in the United States, particularly along the Mid-Atlantic coast. The mechanism by and the extent to which arsenic may be released in contaminated coastal soils due to sea level rise are unknown. Here we show a series of data from a coastal arsenic-contaminated soil exposed to sea and river waters in biogeochemical microcosm reactors across field-validated redox conditions. We find that reducing conditions lead to arsenic release from historically contaminated coastal soils through reductive dissolution of arsenic-bearing mineral oxides in both sea and river water inundations, with less arsenic release from seawater scenarios than river water due to inhibition of oxide dissolution. For the first time, we systematically display gradation of solid phase soil-arsenic speciation across defined redox windows from reducing to oxidizing conditions in natural waters by combining biogeochemical microcosm experiments and X-ray absorption spectroscopy. Our results demonstrate the threat of sea level rise stands to impact arsenic release from contaminated coastal soils by changing redox conditions.

Evidence for exocellular Arsenic in Fronds of Pteris vittata

The arsenic (As) hyperaccumulating fern species Pteris vittata (PV) is capable of accumulating large quantities of As in its aboveground tissues. Transformation to AsIII and vacuolar sequestration is believed to be the As detoxification mechanism in PV. Here we present evidence for a preponderance of exocellular As in fronds of Pteris vittata despite numerous reports of a tolerance mechanism involving intracellular compartmentalization. Results of an extraction experiment show that 43-71% of the As extruded out of the fronds of PV grown in 0.67, 3.3 and 6.7 mM AsV. SEM-EDX analysis showed that As was localized largely on the lower pinna surface, with smaller amounts on the upper surface, as crystalline deposits. X-ray fluorescence imaging of pinna cross-sections revealed preferential localization of As on the pinna surface in the proximity of veins, with the majority localized near the midrib. Majority of the As in the pinnae is contained in the apoplast rather than vacuoles. Our results provide evidence that exocellular sequestration is potentially a mechanism of As detoxification in PV, particularly at higher As concentrations, raising concern about its use for phytoremediation.

Bioaccessibility of Cd and Pb in tailings from a zinc smelting in Brazil: implications for human health

Soils and wastes enriched with heavy metals may present ecological and human health risks. A considerable number of mining areas exist in Brazil, where high levels of metals have been found. However, studies of bioaccessibility of metals in soils/tailings from these areas are scarce, despite their potential informational contribution concerning exposure risks of residents near these areas. This study evaluated tailings collected from four sites of a zinc smelting area located in Brazil with aims to: (1) evaluate the presence of metals of potential concern; (2) investigate Cd and Pb bioaccessibility; and (3) determine the desorption kinetics of Cd and Pb. High concentrations of total Cd and Pb (up to 1743 mg Cd kg(-1) and 8675 mg Pb kg(-1)) and great variability were found in the tailings, indicating the importance of adequate planning for their final disposal, in order to avoid contamination in the surrounding environment. Cadmium and Pb bioaccessibility percentages in the intestinal phase were less than 47 and 4 %, respectively, which represents significant fractions not available for absorption in the intestinal tract. However, this material has to be monitored since its bioaccessibility may increase with eventual physicochemical changes, releasing Cd and Pb. Desorption kinetics experiments revealed that Pb in the samples remained in less labile fractions, whereas Cd was found in more labile fractions, which is in accordance with the bioaccessibility results.

Synchrotron X-ray microfluorescence measurement of metal distributions in Phragmites australis root system in the Yangtze River intertidal zone

This study investigates the distributions of Br, Ca, Cl, Cr, Cu, K, Fe, Mn, Pb, Ti, V and Zn in Phragmites australis root system and the function of Fe nanoparticles in scavenging metals in the root epidermis using synchrotron X-ray microfluorescence, synchrotron transmission X-ray microscope measurement and synchrotron X-ray absorption near-edge structure techniques. The purpose of this study is to understand the mobility of metals in wetland plant root systems after their uptake from rhizosphere soils. Phragmites australis samples were collected in the Yangtze River intertidal zone in July 2013. The results indicate that Fe nanoparticles are present in the root epidermis and that other metals correlate significantly with Fe, suggesting that Fe nanoparticles play an important role in metal scavenging in the epidermis.

Synchrotron micro-scale measurement of metal distributions in Phragmites australis and Typha latifolia root tissue from an urban brownfield site

Liberty State Park in New Jersey, USA, is a "brownfield" site containing various levels of contaminants. To investigate metal uptake and distributions in plants on the brownfield site, Phragmites australis and Typha latifolia were collected in Liberty State Park during the growing season (May-September) in 2011 at two sites with the high and low metal loads, respectively. The objective of this study was to understand the metal (Fe, Mn, Cu, Pb and Zn) concentration and spatial distributions in P. australis and T. latifolia root systems with micro-meter scale resolution using synchrotron X-ray microfluorescence (μXRF) and synchrotron X-ray computed microtomography (μCMT) techniques. The root structure measurement by synchrotron μCMT showed that high X-ray attenuation substance appeared in the epidermis. Synchrotron μXRF measurement showed that metal concentrations and distributions in the root cross-section between epidermis and vascular tissue were statistically different. Significant correlations were found between metals (Cu, Mn, Pb and Zn) and Fe in the epidermis, implying that metals were scavenged by Fe oxides. The results from this study suggest that the expression of metal transport and accumulation within the root systems may be element specific. The information derived from this study can improve our current knowledge of the wetland plant ecological function in brownfield remediation.

Investigation of arsenic species in tailings and windblown dust from a gold mining area

Research has shown the presence of high levels of arsenic (up to 2666 mg As kg(-1)) in tailings from a gold mining area of Brazil. This is an important point of attention, generating concerns about impacts on human health. Yet, a recent study showed that As bioaccessibility in the same area was very low (<4.4%). Thus, determination of the direct solid-phase speciation of As in the mine tailings and windblown dust is needed to explain this low bioaccessibility. Mine samples were collected from four subareas and windblown dust from eight sites. Synchrotron-based bulk-X-ray absorption near-edge structure (bulk-XANES) spectroscopy, micro-X-ray absorption near-edge structure (μ-XANES), and μ-X-ray fluorescence (μ-SXRF) spectroscopy were applied to determine As speciation. Bulk-XANES spectra indicated that As occurs as the As(V) oxidation state. Micro-XANES and μ-SXRF analyses revealed that As was also present as arsenopyrite (FeAsS) and its weathering products, but mostly it was As(V) as poorly crystalline ferric arsenate. This supports the findings of low bioaccessible As and highlights the importance of Fe oxides in immobilizing As in the terrestrial environment. All air particulate samples exhibited As-rich particles (up to 313 mg As kg(-1)). The air particulates exhibited solid-phase As species very similar to those found in the mine samples, which indicates that As in the windblown dust is not easily available.

Correlations in distribution and concentration of calcium, copper and iron with zinc in isolated extracellular deposits associated with age-related macular degeneration

Zinc (Zn) is abundantly enriched in sub-retinal pigment epithelial (RPE) deposits, the hallmarks of age-related macular degeneration (AMD), and is thought to play a role in the formation of these deposits. However, it is not known whether Zn is the only metal relevant for sub-RPE deposit formation. Because of their involvement in the pathogenesis of AMD, we determined the concentration and distribution of calcium (Ca), iron (Fe) and copper (Cu) and compared these with Zn in isolated and sectioned macular (MSD), equatorial (PHD) and far peripheral (FPD) sub-RPE deposits from an 86 year old donor eye with post mortem diagnosis of early AMD. The sections were mounted on Zn free microscopy slides and analyzed by microprobe synchrotron X-ray fluorescence (μSXRF). Metal concentrations were determined using spiked sectioned sheep brain matrix standards, prepared the same way as the samples. The heterogeneity of metal distributions was examined using pixel by pixel comparison. The orders of metal concentrations were Ca ⋙ Zn > Fe in all three types of deposits but Cu levels were not distinguishable from background values. Zinc and Ca were consistently present in all deposits but reached highest concentration in MSD. Iron was present in some but not all deposits and was especially enriched in FPD. Correlation analysis indicated considerable variation in metal distribution within and between sub-RPE deposits. The results suggest that Zn and Ca are the most likely contributors to deposit formation especially in MSD, the characteristic risk factor for the development of AMD in the human eye.

Expanding the nuclear forensic toolkit: chemical profiling of uranium ore concentrate particles by synchrotron X-ray microanalysis

Synchrotron microanalysis was used to provide novel advanced characterisation of uranium ore concentrate particles in application to nuclear forensic science.

Quantification of single-cell nanoparticle concentrations and the distribution of these concentrations in cell population

Quantification of nanoparticle uptake into cells is necessary for numerous applications in cellular imaging and therapy. Herein, synchrotron X-ray fluorescence (SXRF) microscopy, a promising tool to quantify elements in plant and animal cells, was employed to quantify and characterize the distribution of titanium dioxide (TiO2) nanosphere uptake in a population of single cells. These results were compared with average nanoparticle concentrations per cell obtained by widely used inductively coupled plasma mass spectrometry (ICP-MS). The results show that nanoparticle concentrations per cell quantified by SXRF were of one to two orders of magnitude greater compared with ICP-MS. The SXRF results also indicate a Gaussian distribution of the nanoparticle concentration per cell. The results suggest that issues relevant to the field of single-cell analysis, the limitation of methods to determine physical parameters from large population averages leading to potentially misleading information and the lack of any information about the cellular heterogeneity are equally relevant for quantification of nanoparticles in cell populations.

Residence time effects on phase transformation of nanosilver in reduced soils

Residence time effects on phase transformation of silver nanoparticles (AgNPs) (15-50 nm, with and without polyvinylpyrrolidone (PVP) coating) were investigated in reducing soils using experimental geochemistry and synchrotron-based x-ray techniques. After 30 days of anaerobic incubation, a substantial fraction of PVP-coated AgNPs (15 nm) were transformed into Ag₂S and or humic acid (HA) complexed Ag(I), whereas only the HA fraction was dominant in uncoated AgNPs (50 nm). Several investigations recently reported that sulfidation of AgNPs to Ag₂S was the predominant mechanism controlling the fate of AgNP in soil-water environments. However, this investigation showed each AgNP underwent particle-specific chemical transformations to different end compounds after 30 days. Considering the small contribution of Ag(I) dissolution from all AgNPs (less than 5%), we concluded that changes in solid-state chemical speciation of sorbed AgNPs was promoted by particle-specific interactions of NPs in soil chemical constituents, suggesting a critical role of soil absorbents in predicting the fate of AgNPs in terrestrial environments.

Stability of solid-phase selenium species in fly ash after prolonged submersion in a natural river system

Selenium (Se) chemistry can be very complex in the natural environment, exhibiting different valence states (-2, 0, +4, +6) representing multiple inorganic, methylated, or complexed forms. Since redox associated shifts among most of known Se species can occur at environmentally relevant conditions, it is important to identify these species in order to assess their potential toxicity to organisms. In June of 2009, researchers from the US Army Engineer Research & Development Center (ERDC) conducted investigations of the fly ash spilled 6 months previously into the Emory River at the TVA Kingston Fossil Plant, TN. Ash samples were collected on site from both the original ash pile (that did not move during the levee failure), from the spill zone (including the Emory River), and from the ash recovery ditch (ARD) containing ash removed during dredging cleanup operations. The purpose of this work was to determine the state of Se in the spilled fly ash and to assess its potential for transformation and resultant chemical stability from its prolonged submersion in the river and subsequent dredging. Sequential chemical extractions suggested that the river environment shifted Se distribution toward organic/sulfide species. Speciation studies by bulk XANES analysis on fly ash samples showed that a substantial portion of the Se in the original ash pile had transformed from inorganic selenite to a mixture of Se sulfide and reduced (organo)selenium (Se(-II)) species over the 6-month period. μ-XRF mapping data showed that significant trends in the co-location of Se domains with sulfur and ash heavy metals. Ten-d extended elutriate tests (EETs) that were bubbled continuously with atmospheric air to simulate worst-case oxidizing conditions during dredging showed no discernible change in the speciation of fly ash selenium. The enhanced stability of the organo- and sulfide-selenium species coincided with the mixture of the ash material with humic materials in the river, corresponding with notable shifts in the ash carbon- and nitrogen-functionality.

Contrasting calcium localization and speciation in leaves of the Medicago truncatula mutant cod5 analyzed via synchrotron X-ray techniques

Oxalate-producing plants accumulate calcium oxalate crystals (CaOx(c)) in the range of 3-80% w/w of their dry weight, reducing calcium (Ca) bioavailability. The calcium oxalate deficient 5 (cod5) mutant of Medicago truncatula has been previously shown to contain similar Ca concentrations to wild-type (WT) plants, but lower oxalate and CaOx(c) concentrations. We imaged the Ca distribution in WT and cod5 leaflets via synchrotron X-ray fluorescence mapping (SXRF). We observed a difference in the Ca distribution between cod5 and WT leaflets, manifested as an abundance of Ca in the interveinal areas and a lack of Ca along the secondary veins in cod5, i.e. the opposite of what is observed in WT. X-ray microdiffraction (μXRD) of M. truncatula leaves confirmed that crystalline CaOx(c) (whewellite; CaC2 O4 · H2 O) was present in the WT only, in cells sheathing the secondary veins. Together with μXRD, microbeam Ca K-edge X-ray absorption near-edge structure spectroscopy (μXANES) indicated that, among the forms of CaOx, i.e. crystalline or amorphous, only amorphous CaOx was present in cod5. These results demonstrate that deletion of COD5 changes both Ca localization and the form of CaOx within leaflets.

Lead accumulation and association with Fe on Typha latifolia root from an urban brownfield site

Synchrotron X-ray microfluorescence and X-ray absorption near-edge microstructure spectroscopy techniques were applied to Typha latifolia (cattail) root sections and rhizosphere soils collected from a brownfield site in New Jersey to investigate lead (Pb) accumulation in T. latifolia roots and the role of iron (Fe) plaque in controlling Pb uptake. We found that Pb and Fe spatial distribution patterns in the root tissues are similar with both metals present at high concentrations mainly in the epidermis and at low concentrations in the vascular tissue (xylem and phloem), and the major Pb and Fe species in T. latifolia root are Pb(II) and Fe(III) regardless of concentration levels. The sequestration of Pb by T. latifolia roots suggests a potential low-cost remediation method (phytostabilization) to manage Pb-contaminated sediments for brownfield remediation while performing wetland rehabilitation.

Dissolution-Driven Permeability Reduction of a Fractured Carbonate Caprock

Geochemical reactions may alter the permeability of leakage pathways in caprocks, which serve a critical role in confining CO₂ in geologic carbon sequestration. A caprock specimen from a carbonate formation in the Michigan sedimentary Basin was fractured and studied in a high-pressure core flow experiment. Inflowing brine was saturated with CO₂ at 40°C and 10 MPa, resulting in an initial pH of 4.6, and had a calcite saturation index of -0.8. Fracture permeability decreased during the experiment, but subsequent analyses did not reveal calcite precipitation. Instead, experimental observations indicate that calcite dissolution along the fracture pathway led to mobilization of less soluble mineral particles that clogged the flow path. Analyses of core sections via electron microscopy, synchrotron-based X-ray diffraction imaging, and the first application of microbeam Ca K-edge X-ray absorption near edge structure, provided evidence that these occlusions were fragments from the host rock rather than secondary precipitates. X-ray computed tomography showed a significant loss of rock mass within preferential flow paths, suggesting that dissolution also removed critical asperities and caused mechanical closure of the fracture. The decrease in fracture permeability despite a net removal of material along the fracture pathway demonstrates a nonintuitive, inverse relationship between dissolution and permeability evolution in a fractured carbonate caprock.

Parathyroid hormone response to severe vitamin D deficiency is sex associated: an observational study of 571 hip fracture inpatients

OBJECTIVES

To investigate the association between sex and parathyroid hormone response to severe vitamin D deficiency after hip fracture.

DESIGN

Cross-sectional study.

SETTING

Rehabilitation hospital in Italy.

PARTICIPANTS

571 consecutive inpatients with hip fracture and severe vitamin D deficiency (serum 25-hydroxyvitamin D < 12ng/ml), without hypercalcemia or estimated glomerular filtration rate (GFR) < 15ml/min.

MEASUREMENTS

In each patient we assessed PTH (by two-site chemiluminescent enzyme-labelled immunometric assay), 25-hydroxyvitamin D (by immunoenzymatic assay), albumin-adjusted total calcium, phosphate, magnesium, and creatinine 21.3 ± 6.1 (mean ± SD) days after fracture occurrence. Functional level was assessed using the Barthel index. PTH response to vitamin D deficiency was classified as either secondary hyperparathyroidism (serum PTH >75pg/ml) or functional hypoparathyroidism, i.e., inappropriate normal levels of PTH (≤75pg/ml).

RESULTS

Among the 571 patients, 336 (59%) had functional hypoparathyroidism, whereas 235 (41%) had secondary hyperparathyroidism. PTH status was significantly different between sexes (p=0.003): we found functional hypoparathyroidism in 61% of women and 43% of men (secondary hyperparathyroidism in 39% of women and 57% of men). The significance of the between-sex difference was maintained after adjustment for age, estimated GFR, phosphate, albumin-adjusted total calcium, albumin, Barthel index scores, 25-hydroxyvitamin D, and hip fracture type (either cervical or trochanteric). The adjusted odds ratio was 1.85 (95%CI from 1.09 to 3.13; p=0.023).

CONCLUSIONS

Data shows that PTH response to vitamin D deficiency was sex-associated following a fracture of the hip. The higher prevalence of secondary hyperparathyroidism may play a role in the known prognostic disadvantage found in hip-fracture men.

Arsenic and chromium speciation in an urban contaminated soil

The distribution and speciation of As and Cr in a contaminated soil were studied by synchrotron-based X-ray microfluorescence (μ-XRF), microfocused X-ray absorption spectroscopy (μ-XAS), and bulk extended X-ray absorption fine structure spectroscopy (EXAFS). The soil was taken from a park in Wilmington, DE, which had been an important center for the leather tanning industry along the Atlantic seaboard of the United States, until the early 20th century. Soil concentrations of As, Cr, and Pb measured at certain locations in the park greatly exceeded the background levels of these heavy metals in the State of Delaware. Results show that Cr(III) and As(V) species are mainly present in the soil, with insignificant amounts of Cr(VI) and As(III). Micro-XRF maps show that Cr and Fe are distributed together in regions where their concentrations are diffuse, and at local spots where their concentrations are high. Iron oxides, which can reduce Cr(VI) to Cr(III), are present at some of these hot spots where Cr and Fe are highly concentrated. Arsenic is mainly associated with Al in the soil, and to a minor extent with Fe. Arsenate may be sorbed to aluminum oxides, which might have transformed after a long period of time into an As-Al precipitate phase, having a structure and chemical composition similar to mansfieldite (AlAsO(4)⋅2H(2)O). The latter hypothesis is supported by the fact that only a small amount of As present in the soil was desorbed using the characteristic toxicity leaching procedure tests. This suggests that As is immobilized in the soil.

Adherence to recommendations for fall prevention significantly affects the risk of falling after hip fracture: post-hoc analyses of a quasi-randomized controlled trial

BACKGROUND

Few studies focused on fall prevention in hip-fracture survivors.

AIM

To investigate the role of adherence to targeted recommendations on both home environment and behaviors in affecting the hazard of falling after a fall-related hip fracture.

DESIGN

Post-hoc analysis of a quasi-randomized controlled trial.

SETTING

Post-acute rehabilitation hospital.

POPULATION

Ninety-five of 119 women living in the community with a fall-related fracture of the hip.

METHODS

We assessed home hazard of falling and suggested targeted modifications of home environment and behaviors in activities of daily living to prevent falls during inpatient rehabilitation. Falls were recorded at a six-month follow-up during a pre-planned home visit.

RESULTS

Nineteen of the 95 women sustained at least one fall during the six-month follow-up. Women with > 2 uncorrected risk factors had a significantly higher risk of falling than those with 0-2 risk factors; the odds ratio adjusted for four confounders was 4.58 (95%CI 1.472-4.250; P=0.009). Adherence to recommendations for fall prevention was negatively associated with fall risk. The adjusted odds ratio for a ten percent increase in adherence rate was 0.749 (95%CI 0.594-0.945; P=0.015).

CONCLUSION

Uncorrected environmental and behavioral risk factors and poor adherence to targeted recommendations for fall prevention significantly predicted the risk of falling in community-dwelling women who sustained a fall-related hip fracture.

CLINICAL REHABILITATION IMPACT

Fall-risk assessment should be performed during inpatient rehabilitation following a fall-related hip fracture. Improving adherence to targeted recommendations emerges as a major goal to prevent falls in hip-fracture survivors.

Combined application of QEM-SEM and hard X-ray microscopy to determine mineralogical associations and chemical speciation of trace metals

We describe the application of quantitative evaluation of mineralogy by scanning electron microscopy in combination with techniques commonly available at hard X-ray microprobes to define the mineralogical environment of a bauxite residue core segment with the more specific aim of determining the speciation of trace metals (e.g., Ti, V, Cr, and Mn) within the mineral matrix. Successful trace metal speciation in heterogeneous matrices, such as those encountered in soils or mineral residues, relies on a combination of techniques including spectroscopy, microscopy, diffraction, and wet chemical and physical experiments. Of substantial interest is the ability to define the mineralogy of a sample to infer redox behavior, pH buffering, and mineral-water interfaces that are likely to interact with trace metals through adsorption, coprecipitation, dissolution, or electron transfer reactions. Quantitative evaluation of mineralogy by scanning electron microscopy coupled with micro-focused X-ray diffraction, micro-X-ray fluorescence, and micro-X-ray absorption near edge structure (mXANES) spectroscopy provided detailed insights into the composition of mineral assemblages and their effect on trace metal speciation during this investigation. In the sample investigated, titanium occurs as poorly ordered ilmenite, as rutile, and is substituted in iron oxides. Manganese's spatial correlation to Ti is closely linked to ilmenite, where it appears to substitute for Fe and Ti in the ilmenite structure based on its mXANES signature. Vanadium is associated with ilmenite and goethite but always assumes the +4 oxidation state, whereas chromium is predominantly in the +3 oxidation state and solely associated with iron oxides (goethite and hematite) and appears to substitute for Fe in the goethite structure.

Rehabilitation after total hip arthroplasty: a systematic review of controlled trials on physical exercise programs

Total hip arthroplasty (THA) has revolutionized the care of patients with end-stage joint disease, leading to pain relief, functional recovery, and substantial improvement in quality of life. However, long-term studies indicate persistence of impairment and functional limitation after THA, and the optimal rehabilitation protocols are largely unknown. The aim of this paper was to systematically review the controlled trials published on the effectiveness of physical exercise programs after THA. Nine studies were retrieved from MEDLINE and reviewed. Results show that the physical exercise protocols most frequently used after THA in the early postoperative phase are neither supported nor denied by clinical controlled trials. Convincing evidence for the effectiveness of single interventions in addition to usual exercise programs exists for each of the three following options: treadmill training with partial body-weight support, unilateral resistance training of the quadriceps muscle (operated side), and arm-interval exercises with an arm ergometer. In the late postoperative phase (operation interval > 8 weeks) exercise programs consistently improve both impairment and ability to function. Weight-bearing exercises with hip-abductor eccentric strengthening may be the crucial component of the late-phase protocols. Substantial limitations were found in the nine studies, including small sample size, patient selection, heterogeneity of outcome assessments, and potential sources of variability not investigated. Despite limitations, we conclude that three main suggestions emerge from controlled trials on physical exercise after THA: early postoperative protocols should include additive interventions whose effectiveness has been shown. Late postoperative programs are useful and should comprise weight-bearing exercises with hip-abductor eccentric strengthening.

Hip-fracture type does not affect the functional outcome after acute in-patient rehabilitation: a study of 684 elderly women

AIM

To investigate differences in the functional outcome between women sustaining cervical or trochanteric fractures of the hip.

METHODS

We studied 684 of 736 women admitted consecutively to a rehabilitation hospital in Italy because of their first hip fracture. Functional recovery was assessed by using Barthel index scores. Fractures were classified as either cervical (n=335) or trochanteric (n=349) on the basis of surgical and radiographic findings.

RESULTS

After acute in-patient rehabilitation, women with trochanteric fracture had a significantly lower Barthel index score than women with cervical fracture (median values were 85 and 90 respectively, interquartile ranges were 25 and 30 respectively, P=0.001). Length of stay in the hospital was significantly longer in women with trochanteric fractures (median was 37 days vs 36 days; interquartile range was 10 days vs 8 days, P=0.018). However, the differences between the two groups were no longer significant after adjustment for eight variables that affect functional ability in the same population (i.e., age, pressure ulcers, cognitive impairment, neurologic impairment, infections during the length of stay, bone mineral density, body mass index, and Barthel index scores assessed before rehabilitation). Further-more, we found no significant differences in the change of Barthel index scores during rehabilitation and in Barthel index efficiency (change in the Barthel index score after rehabilitation divided by the length of stay in hospital) between the two groups of women.

CONCLUSIONS

After adjustment for several confounders, we did not show significant differences in the functional outcome between women with cervical or trochanteric fracture of the hip.

Hyperaccumulator Alyssum murale relies on a different metal storage mechanism for cobalt than for nickel

The nickel (Ni) hyperaccumulator Alyssum murale has been developed as a commercial crop for phytoremediation/phytomining Ni from metal-enriched soils. Here, metal co-tolerance, accumulation and localization were investigated for A. murale exposed to metal co-contaminants. A. murale was irrigated with Ni-enriched nutrient solutions containing basal or elevated concentrations of cobalt (Co) or zinc (Zn). Metal localization and elemental associations were investigated in situ with synchrotron X-ray microfluorescence (SXRF) and computed-microtomography (CMT). A. murale hyperaccumulated Ni and Co (> 1000 microg g(-1) dry weight) from mixed-metal systems. Zinc was not hyperaccumulated. Elevated Co or Zn concentrations did not alter Ni accumulation or localization. SXRF images showed uniform Ni distribution in leaves and preferential localization of Co near leaf tips/margins. CMT images revealed that leaf epidermal tissue was enriched with Ni but devoid of Co, that Co was localized in the apoplasm of leaf ground tissue and that Co was sequestered on leaf surfaces near the tips/margins. Cobalt-rich mineral precipitate(s) form on leaves of Co-treated A. murale. Specialized biochemical processes linked with Ni (hyper)tolerance in A. murale do not confer (hyper)tolerance to Co. A. murale relies on a different metal storage mechanism for Co (exocellular sequestration) than for Ni (vacuolar sequestration).

Diagnostic value of prealbumin and retinol-binding protein in acute and chronic liver diseases

Prealbumin (PA) and retinol-binding protein (RBP) serum concentrations have been determined in 161 patients with different chronic and acute liver diseases and in 49 healthy controls. Their possible role in clinical practice as liver markers of hepatic biosynthesis in comparison with other traditional tests: albumin, pseudocholinesterase and clotting factors II, VII and X associated activity (Hepato-Quick) was investigated. PA and RBP were always highly intercorrelated and significantly decreased in acute viral hepatitis, steatosis, chronic persistent and active hepatitis, cirrhosis, hepatic tumors and primary biliary cirrhosis. Among the different tests, PA and RBP presented the best values of specificity (0.98 and 0.97, respectively), sensitivity (0.77 and 0.73) and positive (0.99) and negative prediction (0.57 and 0.46). In chronic liver diseases PA and RBP distinguished more efficiently than the other biosynthetic markers among diseases with different degree of severity. In acute viral hepatitis the behavior of PA and RBP, followed for 4 consecutive weeks, was similar to that of Hepato-Quick and better than the other tests in reflecting the clinical course of the disease.