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[Display omitted] • Unaltered lung tissue samples from former asbestos workers were studied. • Combined x-ray tomography and x-ray spectroscopy were exploited. • The 3D morphology and mass density of selected asbestos bodies were revealed. • Quantitative elemental analysis revealed similar composition of the asbestos bodies. • The Fe content in the asbestos bodies was higher than that contained in asbestos. In the lungs, asbestos develops an Fe-rich coating (Asbestos Body, AB) that becomes the actual interface between the foreign fibers and the host organism. Conventional approaches to study ABs require an invasive sample preparation that can alter them. In this work, a novel combination of x-ray tomography and spectroscopy allowed studying unaltered lung tissue samples with chrysotile and crocidolite asbestos. The thickness and mass density maps of the ABs obtained by x-ray tomography were used to derive a truly quantitative elemental analysis from scanning x-ray fluorescence spectroscopy data. The average mass density of the ABs is compatible with that of highly loaded ferritin, or hemosiderin. The composition of all ABs analyzed was similar, with only minor differences in the relative elemental fractions. Silicon concentration decreased in the core-to-rim direction, indicating a possible partial dissolution of the inner fiber. The Fe content in the ABs was higher than that possibly contained in chrysotile and crocidolite. This finding opens two opposite scenarios, the first with Fe coming from the fiber bulk and concentrating on the surface as long as the fiber dissolves, the second where the Fe that takes part to the formation of the AB originates from the host organism Fe-pool. [ABSTRACT FROM AUTHOR]

The number of the Asbestos Bodies (AB), i.e. asbestos that developed an iron-protein coating during its permanence in biological tissues, is one of the most accessible markers of asbestos exposure in individuals. The approaches developed to perform AB count in biological tissues are based on the manual examination of tissue digests or histological sections by means of light or electron microscopies. Although these approaches are well established and relatively accessible, manual examination is time-consuming and can be reader-dependent. Besides, approximations are applied because of the limitations of 2D readings and to speed up manual counts. In addition, sample preparation using tissue digests require an amount of tissue that can only be obtained by invasive surgery or post-mortem sampling. In this paper, we propose a new approach to AB counting based on non-destructive 3D imaging, which has the potential to overcome most of the limitations of conventional approaches. This method allows automating the AB count and determining their morphometry distribution in bulk tissue samples (ideally non-invasive needle biopsies), with minimal sample preparation and avoiding approximations. Although the results are promising, additional testing on a larger number of AB-containing biological samples would be required to fully validate the method. [ABSTRACT FROM AUTHOR]

We report on the synthesis and As adsorption properties of a novel chitosan – iron (oxyhydr)oxide composite material for the remediation of arsenic-contaminated water supplies. FE-SEM, Mössbauer spectroscopy, ICP-OES and synchrotron (Bulk XAS, μXRF) techniques were applied to determine the composition of the new material and investigate the As uptake efficiency and mechanism. The iron (oxyhydr)oxide phase has been identified as a nano-sized goethite, well dispersed in the chitosan matrix, leading to the name ‘chitosan goethite bionanocomposite’ (CGB). The CGB material is prepared in the form of beads of high density and excellent compression strength; the embedding of the goethite nanoparticles in the chitosan matrix allows for the high adsorption capacity of nanoparticles to be realized. CGB beads remove both As(III) and As(V) efficiently from water, over the pH range 5–9, negating the need for pre-oxidation of As(III). Kinetic studies and μXRF analysis of CGB bead sections show that diffusion-adsorption of As(V) into CGB beads is faster than for As(III). Using CGB beads, synthetic high-arsenic water (0.5 mg-As/L) could be purified to world drinking standard level (<0.01 mg-As/L) using only 1.4 g/L CGB. When considered in combination with the advantages of the low-cost of raw materials required, and facile (green) synthesis route, CGB is a promising material for arsenic remediation, particularly in developing countries, which suffer a diversity of socio-economical-traditional constraints for water purification and sanitation. [ABSTRACT FROM AUTHOR]

Sodium montmorillonite (Na–Mt) was synthesized with the aim to investigate the adsorption and diffusion of hydrogen gas in a model smectite at high pressures (up to 90 bar) and non-cryogenic temperature (363 K). Na–Mt samples were synthesized from hydrogels in mild conditions (493 K and autogenous pressure). Two further Na–Mt samples with different levels of structural iron were prepared to investigate the effect of iron on the textural and hydrogen adsorption properties. Structural and elemental analyses confirmed that well crystalline smectite samples were obtained according to the nominal chemical formulae. Nitrogen adsorption–desorption isotherms revealed that the synthesized materials have specific areas in the range 90–120 m 2 /g and are mainly mesoporous. High pressure volumetric measurements showed that hydrogen absorption at 363 K saturated between 40 and 60 bar, reaching 0.2 ± 0.02 wt% (i.e. ∼1.0 mmol/g) at the plateau. Quasi-elastic neutron scattering revealed that hydrogen diffuses inside the clay porous network according to the Fick's law (continuous diffusion), while jump diffusion cannot be excluded at distances lower than 6.3 Å, i.e. less than the one between two Na + exchangeable ions. The hydrogen self-diffusion coefficients in the temperature range 25–300 K were determined to fall in the interval 0.1–1.0 · 10 −7 m 2 s −1 . The results are compared with H 2 (g) adsorption and diffusion in other systems. [ABSTRACT FROM AUTHOR]

The Callovo-Oxfordian clay-rich rock formation is currently considered as host rock barrier in the French geological repository facility for radioactive waste (Meuse/Haute-Marne). After the closure of the facility, hydrogen gas is expected to develop mainly from anaerobic corrosion of steel containers and other iron-containing structures. Gas pressure build-up could impact the safety of the repository. It is therefore important to acquire in-depth knowledge on the interaction between hydrogen gas and surrounding clay rock in terms of uptake ability and diffusion. Hydrogen uptake capacity was evaluated on dried clay rock samples: (i) at 20 K, to allow for hydrogen liquefaction and determine the maximal H 2 uptake of the clay, and (ii) at typical pressure and temperature conditions expected to develop in the repository (up to 363 K and a hydrogen pressure of 40–60 bar). H 2 absorption on the dried raw Callovo-Oxfordian start to saturate at about 30–40 bar, and the average adsorption above 40 bar is about 0.1% in weight. Quasi-elastic neutron scattering spectroscopy was used to study the diffusion mechanism of hydrogen gas in the clay rock at the microscopic scale and to determine hydrogen self-diffusion coefficients in the dry samples in the temperature range 25–300 K. Neutron data suggested that hydrogen diffuses in the dry clay rock according to Fick’s law. The findings reported in this work can help to better understand the behavior of H 2 in clay rock samples. [ABSTRACT FROM AUTHOR]

The interaction of an As-rich natural pyrite (FeS2.08As0.043) with aqueous Se(IV) was investigated as a function of pH, ferrous iron concentration, and reaction time. Arsenic is often the most abundant minor constituent of natural pyrite, and is believed to substitute for S in the pyrite structure. EXAFS measurements confirmed the presence of AsS dianion group, with arsenic in the same local configuration as in the arsenopyrite. Speciation studies indicated that Se(0) was the unique reduction product in the pH range 5.05-8.65 over a reaction period of >1month, while trace amounts of FeSeO3 might be formed at pH⩾6.10. At pH>6.07, the formation of Fe(III)-(oxyhydr)oxide is kinetically favored, and it consumed nearly all the aqueous iron, including the extra added Fe2+, thereby inhibiting the formation of the thermodynamically most stable product: FeSe2. After oxidation by Se(IV), the occurrence of surface S0, significant aqueous sulfur deficit, and excessive leaching of arsenic in solution, indicate the preferential release of As impurity via arsenopyrite oxidation. The data suggest that the polysulfide-elemental sulfur pathway, which prevails in acid-soluble metal sulfides, is an important pathway in the oxidation of As-rich pyrite, in addition to the thiosulfate pathway for acid-insoluble pyrite. Control experiments on As-free natural pyrite further support this mechanism. This study confirms the potential of reductive precipitation to attenuate the mobility of Se in the environment and demonstrates that minor elements commonly present in natural pyrite can play a significant role on its dissolution pathway. [ABSTRACT FROM AUTHOR]

A fundamental step to evaluate the biogeochemical and eco-toxicological significance of Hg dispersion in the environment is to determine speciation of Hg in solid matrices. In this study, several analytical techniques such as scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), sequential chemical extractions (SCEs), and X-ray absorption spectroscopy (XANES) were used to identify Hg compounds and Hg speciation in samples collected from the Mt. Amiata Hg mining district, southern Tuscany, Italy. Different geological materials, such as mine waste calcine (retorted ore), soil, stream sediment, and stream water suspended particulate matter were analyzed. Results show that the samples were generally composed of highly insoluble Hg compounds such as sulphides (HgS, cinnabar and metacinnabar), and more soluble Hg halides such as those associated with the mosesite group. Other moderately soluble Hg compounds, HgCl 2 , HgO and Hg 0 , were also identified in stream sediments draining the mining area. The presence of these minerals suggests active and continuous runoff of soluble Hg compounds from calcines, where such Hg compounds form during retorting, or later in secondary processes. Specifically, we suggest that, due to the proximity of Hg mines to the urban center of Abbadia San Salvatore, the influence of other anthropogenic activities was a key factor for Hg speciation, resulting in the formation of unusual Hg-minerals such as mosesite. [ABSTRACT FROM AUTHOR]

Recent studies demonstrated that synthetic calcite may host considerable amounts of arsenic (As). In this paper, the concentration of As in natural calcite was determined using two novel, specifically designed, sequential extraction procedures. In addition, the oxidation state of As and its distribution between calcite and coexisting Fe-oxyhydroxides was unravelled by μXRF elemental mapping and As K-edge μXAS spectroscopy. Our results conclusively demonstrate that arsenic can be found in natural calcite up to 2 orders of magnitude over the normal crustal As abundances. Because of the large diffusion of calcite in the environment, this phase may exert an important control on As geochemistry, mobility, and bioavailability. [ABSTRACT FROM AUTHOR]

The present work reports a detailed investigation on the speciation of iron in the pigments of decorated pottery fragments of cultural heritage relevance. The fragments come from the Gioiosa Guardia archaeological site in the area of the `Strait of Messina' (Sicily, Southern Italy), and date back to VI-V century BC. The purpose of this study is to characterize the main pigmenting agents responsible for the dark-red coloration of the specimens using non-destructive analytical techniques such as synchrotron radiation X-ray absorption spectroscopy (SR-XAS), a well established technique for cultural heritage and environmental subjects. Absorption spectra were collected at the Fe K-edge on the Italian beamline for absorption and diffraction (BM8-GILDA) at the European Synchrotron Radiation Facility in Grenoble (France). In order to determine the speciation of Fe in the samples, principal component analysis and least-squares fitting procedures were applied to the near-edge part of the absorption spectra (XANES). Details on the local structure around the Fe sites were obtained by analyzing the extended part of the spectra (EXAFS). Furthermore, an accurate determination of the average Fe oxidation state was carried out through analysis of the pre-edge peaks of the absorption spectra. Samples resulted composed of an admixture of Fe2O3 (hematite or maghemite) and magnetite (Fe3O4), occurring in different relative abundance in the dark- and light-colored areas of the specimens. The results obtained are complementary to information previously obtained by means of instrumental neutron activation analysis, Fourier transform infrared absorbance and time-of-flight neutron diffraction. [ABSTRACT FROM AUTHOR]

Abstract: X-ray Absorption Spectroscopy (XAS), X-Ray Diffraction (XRD), Thermo-Gravimetric Analysis (TGA) and Scanning Electron Microscopy–Energy Dispersive Spectroscopy (SEM–EDS) techniques were used to determine the composition and the speciation of Fe and Mn in road dust samples collected in the Traforo del San Bernardo highway tunnel. Principal Component Analysis and Least Square Fitting on the XANES region of the absorption spectra and structural refinements on the EXAFS part of the spectra were applied to obtain complementary information on the speciation, average oxidation state, and local structure of Fe and Mn. XRD indicated the presence of silica, calcite, gypsum, and of various phyllosilicates. TGA analysis confirmed the presence of phyllosilicates and also detected a significant amount of organic phases. These findings indicate the co-presence of particles of natural origin along with the organic phases related to vehicular gas exhausts emission. On the other hand, XAS analysis showed that iron is mainly present in the Fe3O4 and FeCl3 forms, which can be considered to have both anthropic origin, i.e., exhaust emission and salt used to prevent ice formation, respectively. [Copyright &y& Elsevier]

We report on a non-destructive study of Sicilian ceramic fragments of cultural heritage interest, classified as 'proto-majolica' pottery and dating back to the twelfth to thirteen centuries AD. The analytical approach used is based on the employment of two totally non-invasive spectroscopic techniques: X-ray fluorescence (XRF), using a portable energy-dispersive XRF analyser, and X-ray absorption spectroscopy, using synchrotron radiation as a probe (SR-XAS). XRF measurements allowed us to collect elemental and spatially resolved information on major and minor constituents of the decorated coating of archaeological pottery fragments, so providing preliminary results on the main components characterizing the surface. In particular, we assigned to Fe and Mn the role of key elements of the colouring agent. With the aim of obtaining more detailed information, we performed SR-XAS measurements at the Fe and Mn K-edges at the Italian BM08 beamline at the European Synchrotron Radiation Facility (Grenoble, France). The experimental data were analysed by applying principal component analysis and least-squares fitting to the near-edge part of the spectra (X-ray absorption near-edge structure) to determine the samples' speciation. From the overall results, umber, a class of brownish pigments characterized by a mixture of hydrated iron and manganese oxides, has been ascribed as a pigmenting agent. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Biotite is a constituent Fe-bearing mineral of Delta subsoils in India and Bangladesh and has been hypothesized as a primary source of arsenic (As). The adsorption behavior of As onto structural Fe(II, III)-bearing biotite fractions (<50μm) was investigated in the pH range of 4–8 under a CO2-free, anoxic condition (O2 <1ppmv) using X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The batch experiments indicate that As adsorption is strongly pH dependent and that As(V) adsorbs more efficiently than As(III). X-ray Absorption Near-Edge Structure (XANES) spectra show no oxidation or reduction of As by biotite after reaction with As(III) or As(V) solutions for 3days. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopic results suggest that As(III) forms bidentate mononuclear edge-sharing (2E) and bidentate binuclear corner-sharing (2C) surface complexes at pH 7.7 as indicated by average As–Fe bond distances at 3.00±0.02Å and 3.37±0.03Å respectively. The surface speciation retrieved by XPS does not provide any evidence of reduction of As(V) on biotite after 30days further confirming the thermodynamic prediction and the XANES results. This study has therefore significant environmental implications for As contaminated areas, where biotite retards the release of As into reducing groundwater. The changes in soil redox conditions and weathering of biotite may likely contribute to the occurrence of high As in groundwater. [ABSTRACT FROM AUTHOR]

The reductive immobilization of Se(IV) by micrometer-sized (100-200 μm) calcite containing sorbed or coprecipitated Fe(II) was investigated at pH 7 under anoxic conditions (O2 < 1 ppmv) using X-ray absorption near-edge structure (XANES) spectroscopy. The Se(IV) sorption on calcite increased in the presence of sorbed Fe(II) compared to that of Fe-free pure calcite. XANES spectra of Se K-edge shows that nearly half of the total sorbed Se(IV) is reduced to Se(0) by Fe(II) sorbed on calcite within 24 h. The extent of reduction decreases with increasing equilibration time of calcite with Fe(II) solution before Se(IV) addition. The combined results of field emission scanning electron microscopy and X-ray diffraction have shown that needle-shaped red monoclinic elemental Se with diameters of 30-50 nm and lengths of up to 100 nm is precipitated on the calcite surface. Fe(II) coprecipitated calcite does not contribute to Se(IV) reduction within 72 h. Therefore, the reduction capacity of Fe(II) linked to calcite critically depends on its location (either on the surface or in the bulk solid), and less extensively on the pre-equilibration time of calcite with Fe(II) solution. Such understanding is important to predict the transport, transformation, and attenuation of Se in subsurface and in nuclear waste repositories. [ABSTRACT FROM AUTHOR]

• A complex mineralogical assemblage was revealed. • Fe(II) and Fe(III) species were detected in a variety of coordination environments. • The Fe oxidation state and speciation is not affected by water. • Significant changes were evidenced as a function of particle granulometry. • Ashes surface features may prevent direct exposure to mobile and toxic Fe(II). Volcanic ashes particles are subjected to substantial modification during explosive eruptions. The mineralogical and compositional changes have important consequences on the environment and human health. Nevertheless, the relationship between the speciation of iron (Fe) and the mineralogical composition and particle granulometry of the ashes, along with their interaction with water, are largely unknown. In particular, the Fe oxidation state and the possible formation of new Fe-bearing phases in presence of S, Cl, and F in the plume are key points to assess the impact of the ashes. Fragmental material ejected during volcanic activity (tephra) in 2013, was collected on the Mt. Etna (Italy) and investigated using a multi-technique approach that included conventional Electron Paramagnetic Resonance (EPR), high field EPR (HFEPR), EchoEPR, and Fe K-edge X-ray Absorption Spectroscopy (XAS). These element-selective techniques allowed obtaining a detailed information on the oxidation state and coordination environment of Fe, and of its speciation in the ash samples as a function of the granulometry. A complex mineralogical assemblage, consisting of variable amounts of nanometric crystalline Fe inclusions in a glass matrix, and of Fe-oxides and Fe-sulfur phases was revealed. A risk assessment of the ashes is attempted. [ABSTRACT FROM AUTHOR]

Once penetrated into the lungs of exposed people, asbestos induces an in vivo biomineralisation process that leads to the formation of a ferruginous coating embedding the fibres. The ensemble of the fibre and the coating is referred to as asbestos body and is believed to be responsible for the high toxicological outcome of asbestos. Lung tissue of two individuals subjected to prolonged occupational exposure to crocidolite asbestos was investigated using synchrotron radiation micro-probe tools. The distribution of K and of elements heavier than Fe (Zn, Cu, As, and Ba) in the asbestos bodies was observed for the first time. Elemental quantification, also reported for the first time, confirmed that the coating is highly enriched in Fe (~20% w/w), and x-ray absorption spectroscopy indicated that Fe is in the 3+ oxidation state and that it is present in the form of ferritin or hemosiderin. Comparison of the results obtained studying the asbestos bodies upon removing the biological tissue by chemical digestion and those embedded in histological sections, allowed unambiguously distinguishing the composition of the asbestos bodies, and understanding to what extent the digestion procedure altered their chemical composition. A speculative model is proposed to explain the observed distribution of Fe. [ABSTRACT FROM AUTHOR]

One of the main problems related to ferruginous-asbestos bodies (ABs) exposure is their potential pathogenetic role in asbestos-related diseases. The aim of this study was to examine whether purified ABs, might stimulate inflammatory cells. ABs were isolated by exploiting their magnetic properties, therefore avoiding the strong chemical treatment usually employed for this purpose. This latter treatment, which is based upon the digestion of organic matter with concentrated hypochlorite, may markedly modify the AB structure and consequently also their "in vivo" manifestations. ABs were found to induce secretion of human neutrophil granular component myeloperoxidase, as well as stimulate rat mast cell degranulation. Data demonstrated that by triggering secretory processes in inflammatory cells, purified ABs may play a role in the pathogenesis of asbestos-related diseases by continuing and enhancing the pro-inflammatory activity of the asbestos fibers. [ABSTRACT FROM AUTHOR]

The appropriate selection of representative pure compounds to be used as reference is a crucial step for successful analysis of X-ray absorption near edge spectroscopy (XANES) data, and it is often not a trivial task. This is particularly true when complex environmental matrices are investigated, being their elemental speciation a priori unknown. In this paper, an investigation on the speciation of Cu, Zn, and Sb based on the use of conventional (stoichiometric compounds) and non-conventional (environmental samples or relevant certified materials) references is explored. This method can be useful in when the effectiveness of XANES analysis is limited because of the difficulty in obtaining a set of references sufficiently representative of the investigated samples. Road dust samples collected along the bridge connecting Venice to the mainland were used to show the potentialities and the limits of this approach. [ABSTRACT FROM AUTHOR]

Aqua Traiana is an ancient Roman aqueduct, built to supply water to the ancient city of Rome and still working nowadays. This work is focused on the characterization of its mortars, and in particular the binders, to identify the reasons of such a durable resistance. Samples collected inside the aqueduct were analysed by Optical Microscopy (OM) in thin sections, X-ray Powder Diffraction (XRPD), Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS), High Resolution Field Emission Scanning Electron Microscopy (HR-FESEM-EDS), Electron Microprobe (EMPA), Differential Scanning Calorimetry coupled with Thermogravimetric Analysis (DSC-TGA), Fourier-Transform Infrared spectroscopy (FTIR), X-ray Absorption Near Edge Structure (XANES) spectroscopy and N 2 adsorption/desorption measurements. The presence of an amorphous gel-like C-(N,K)-A-S-H binder and the complete absence of calcite in Trajan Age samples constitute a unique case, and may be the reason of the high hydraulicity of the mortar. Establishing how these features were produced could allow them to be replicated in high-durability and high-compatibility restoration mortars. • Ancient mortars from Aqua Traiana are characterised by a multi-analytical approach. • Trajan mortars have pozzolanic aggregate, amorphous gel-like binder without calcite. • The absence of calcite in Trajan samples constitutes a unique case in history. • The amorphous binder gives better hydraulicity and mechanical strength. • High-durability and green mortars could be produced from ancient recipes. [ABSTRACT FROM AUTHOR]

Abstract: The western part of the Chalkidiki peninsula in Northern Greece is a geothermally active area that contains high levels of naturally derived arsenic in its alkaline groundwaters (up to 3760μg/L). Near wells, equilibration of these groundwaters with atmospheric carbon dioxide leads to the precipitation of travertines that contain very high levels of arsenic (up to 913mg/kg). To determine the mechanism of arsenic uptake in these travertines, we analyzed two different types of travertine from this region using both bulk and micro-focused X-ray absorption spectroscopy (XAS and μ-XAS) and micro-focused X-ray fluorescence spectroscopy (μ-XRF). Bulk XAS showed that in all of the studied samples arsenic is present in the pentavalent oxidation state (arsenate). μ-XRF analyses indicated that arsenic is closely associated with the calcite matrix and that it generally does not correlate well with iron. The arsenic K-edge XAS spectra of all samples closely matched each other and closely resembled a reference spectrum for arsenate coprecipitated with calcite (rather than adsorbed or pure calcium arsenate). Iron on the other hand was found to be mainly present as a constituent of clay minerals, of presumably detrital origin, suggesting that iron-(hydr)oxides were not sufficiently abundant to act as major scavengers for arsenic in the Chalkidiki travertines. We estimated that calcite in these travertines could sequester at least 25% of aqueous arsenic in the form of As(V) and thus immobilize a substantial part of arsenic present in the geothermal groundwaters. These results may also be relevant for other areas where geothermal groundwaters carry arsenic to the surface and possibly as well for arsenic geochemistry in other environments with CO2-enriched water. [Copyright &y& Elsevier]

Abstract: Since reductive precipitation is considered as the most effective way to immobilize 79Se, interaction of aqueous Se(IV)/Se(VI) with Fe(II)-bearing minerals has received extensive attention. In contrast to the thermodynamic calculations, as well as the prevalence of iron selenide phases observed in soil, sediments and ore deposits, most laboratory experiments have found that Se(0) was the reaction product. In this study, the interaction of Se(IV)/Se(VI) with FeSe/FeSe2 were investigated. The results demonstrate that FeSe and FeSe2 can be oxidized to Se(0) by Se(IV) with relatively fast kinetics, while reaction between Se(VI) and FeSe/FeSe2 only occurs under limited conditions (i.e. in the presence of high ferrous content and higher pH) with much slower kinetics, and there is no evident reaction in most case. Therefore, reduction of Se(IV) by Fe(II)-bearing minerals, in particular by natural occurring minerals, is envisioned to produce Se(0) at the early stage of experiments, rather than FeSe or FeSe2. Due to the formation of bulk Se(0) and its low solubility, the Fe–Se–O–H2O system will maintain redox disequilibrium in laboratory time-scale. This study also reveals that iron selenides, like iron sulfides, have strong reactivity toward Fe3+. The findings in this study give insight into possible controls on Se redox process. [Copyright &y& Elsevier]

A nanopyrite/greigite composite was synthesized by reacting FeCl3 and NaHS in a ratio of 1:2 (Wei et al. 1996). Following this procedure, the obtained solid phases consisted of 30-50 nm sized particles containing 28% of greigite (Fe2+Fe3+2S4) and 72% pyrite (FeS2). Batch reactor experiments were performed with selenite or selenate by equilibrating suspensions containing the nanosized pyrite-greigite solid phase at different pH-values and with or without the addition of extra Fe2+. XANES-EXAFS spectroscopic techniques revealed, for the first time, the formation of ferroselite (FeSe2) as the predominant reaction product, along with elemental Se. In the present experimental conditions, at pH 6 and in equilibrium with Se0, the solution is oversaturated with respect to ferrosilite. Furthermore, thermodynamic computations show that reaction kinetics likely played a significant role in our experimental system. [ABSTRACT FROM AUTHOR]

Abstract: Hybrid oxide/carbon composite foams and films were prepared from furfuryl alcohol polymers (PFA) via SnCl2 Lewis acid-catalyzed polymerization and pyrolysis. Structure, morphology and absorptive properties of the porous composites and films were investigated by means of SEM microscopy, XRD, BET analysis and UV–vis spectroscopy. The role of the catalyst concentration and of the thermal treatments were highlighted for both systems. Results concerning the composite foams and films showed that the quality of SnO2 coating was improved upon prolonged thermal treatment at 500°C. Furthermore, the growth behaviour of the SnO2/C and the electrical conductivities of films are also discussed. [Copyright &y& Elsevier]

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder affecting motor neurons. Pre‐clinical studies drive the development of animal models that well mimic ALS disorder and enable both the dissection of disease processes and an early assessment of therapy efficacy. A comprehensive knowledge of neuronal and vascular lesions in the brain and spinal cord is an essential factor to understand the development of the disease. Spatial resolution and bidimensional imaging are important drawbacks limiting current neuroimaging tools, while neuropathology relies on protocols that may alter tissue chemistry and structure. In contrast, recent ex vivo studies in mice demonstrated that X‐ray phase‐contrast tomography enables study of the 3D distribution of both vasculature and neuronal networks, without sample sectioning or use of staining. Here we present our findings on ex vivo SOD1G93A ALS mice spinal cord at a micrometric scale. An unprecedented direct quantification of neuro‐vascular alterations at different stages of the disease is shown. [ABSTRACT FROM AUTHOR]

Abstract The impact of seasonal fluctuations linked to monsoon and irrigation generates redox oscillations in the subsurface, influencing the release of arsenic (As) in aquifers. Here, the biogeochemical control on As mobility was investigated in batch experiments using redox cycling bioreactors and As- and SO 4 2−-amended sediment. Redox potential (E h) oscillations between anoxic (−300–0 mV) and oxic condition (0–500 mV) were implemented by automatically modulating an admixture of N 2 /CO 2 or compressed air. A carbon source (cellobiose, a monomer of cellulose) was added at the beginning of each reducing cycle to stimulate the metabolism of the native microbial community. Results show that successive redox cycles can decrease arsenic mobility by up to 92% during reducing conditions. Anoxic conditions drive mainly the conversion of soluble As(V) to As(III) in contrast to oxic conditions. Phylogenetic analyses of 16S rRNA amplified from the sediments revealed the presence of sulfate and iron – reducing bacteria, confirming that sulfate and iron reduction are key factors for As immobilization from the aqueous phase. As and S K-edge X-ray absorption spectroscopy suggested the association of Fe-(oxyhydr)oxides and the importance of pyrite (FeS 2(s)), rather than poorly ordered mackinawite (FeS (s)), for As sequestration under oxidizing and reducing conditions, respectively. Finally, these findings suggest a role for elemental sulfur in mediating aqueous thioarsenates formation in As-contaminated groundwater of the Mekong delta. Graphical abstract Unlabelled Image Highlights • Microbial sulfate reduction was found to contribute to arsenic (As) sequestration. • During anoxic conditions, the conversion of soluble As(V) to As(III) was observed. • The formation of pyrite, rather than mackinawite was observed in redox cycles. • Absorption/desorption of aqueous As on Fe-(oxyhydr)oxides and pyrite was observed. [ABSTRACT FROM AUTHOR]

Abstract: The fabrication and characterization of conductive tracks by laser irradiation on non-conductive multiwalled carbon nanotube/polyethylene (MWCNT/HDPE) composites is reported. Along the irradiated paths the percolation of MWCNTs is occurring, as demonstrated by field emission scanning electron and atomic force microscopies. An increment of the track conductivity of several orders of magnitude is documented by single pass Kelvin probe force and current sensing atomic force microscopies, together with electrical measurements. The structure of conductive paths has been estimated by secondary electron charge contrast imaging. The investigation has been developed from basic characterization up to industrial scale manufacturing. The method is fast, flexible and innovative, because: (i) highly adherent tracks of any selected pattern on a low cost material can be obtained, (ii) the tracks are metal-free, a fact rendering the composite fully recyclable and (iii) the irradiated materials have application for electrical signals transport; (iv) the tracks are also characterized by piezoresistive properties so allowing their employment as pressure sensors. [Copyright &y& Elsevier]

Abstract: Acid waters and sediments of the Tinto Santa Rosa acid stream (Iberian Pyritic Belt; SW, Spain) were analysed to determine the role of sedimentary phases in the behaviour of arsenic. Aqueous arsenic and iron concentrations decreased markedly from the adit mouth to 300m downstream indicating iron minerals precipitation as well as arsenic sorption onto these newly-formed phases. This was confirmed by the high arsenic concentrations observed in bed-stream precipitates, which play a major role in controlling arsenic mobility. To unravel the complex nature of the AMD sediments a combination of techniques including X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), total solid digestions, X-Ray Fluorescence (XRF) and X-Ray Absorption Spectroscopy (XAS) were employed. Results showed that (1) arsenic was present predominantly in its pentavalent state; (2) upstream arsenic was sorbed onto the main phase, schwertmannite, whereas downstream it was chiefly associated with goethite and jarosite; and (3) changes in arsenic speciation with depth were observed in the consolidated terrace sediments, where arsenic appeared primarily associated with schwertmannite in the upper part of the terraces, but with goethite at depth. Arsenic mobilization was controlled by sorption onto newly formed precipitates (schwertmannite, goethite and jarosite), causing natural arsenic attenuation. [Copyright &y& Elsevier]

Abstract: Mn-K edge EXAFS and XANES spectra of La0.87Na0.13MnO3 manganite films with different thicknesses (750, 250, 125 and 50Å), have been acquired at RT. In the 50Å film a shift of the Fermi level downward in energy is found if compared to the other films. In addition, the density of the empty minority spin states is decreased. This finding has been attributed to the presence of some Mn ions experiencing a different local chemical environment that results in the breaking of some DE paths, and in addition to an Anderson localisation of the charge carriers. This last conclusion can explain both the strongly insulating nature and the spin glass like behaviour of the magnetic response of the 50Å film, and has been corroborated by the results of the EXAFS analysis. [Copyright &y& Elsevier]