I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[10327, 12760, 22244]
Open Access
Abstract: Mineral dust is the largest source of aerosol iron (Fe) to the offshore global ocean, but acidic processing of coal fly ash (CFA) in the atmosphere could be an important source of soluble aerosol Fe. Here, we determined the Fe speciation and dissolution kinetics of CFA from Aberthaw (United Kingdom), Krakow (Poland), and Shandong (China) in solutions which simulate atmospheric acidic processing. In CFA PM10 fractions, 8 %–21.5 % of the total Fe was found to be hematite and goethite (dithionite-extracted Fe), and 2 %–6.5 % was found to be amorphous Fe (ascorbate-extracted Fe), while magnetite (oxalate-extracted Fe) varied from 3 %–22 %. The remaining 50 %–87 % of Fe was associated with other Fe-bearing phases, possibly aluminosilicates. High concentrations of ammonium sulfate ((NH4)2SO4), often found in wet aerosols, increased Fe solubility of CFA up to 7 times at low pH (2–3). The oxalate effect on the Fe dissolution rates at pH 2 varied considerably, depending on the samples, from no impact for Shandong ash to doubled dissolution for Krakow ash. However, this enhancement was suppressed in the presence of high concentrations of (NH4)2SO4. Dissolution of highly reactive (amorphous) Fe was insufficient to explain the high Fe solubility at low pH in CFA, and the modelled dissolution kinetics suggest that other Fe-bearing phases such as magnetite may also dissolve relatively rapidly under acidic conditions. Overall, Fe in CFA dissolved up to 7 times faster than in a Saharan dust precursor sample at pH 2. Based on these laboratory data, we developed a new scheme for the proton- and oxalate-promoted Fe dissolution of CFA, which was implemented into the global atmospheric chemical transport model IMPACT (Integrated Massively Parallel Atmospheric Chemical Transport). The revised model showed a better agreement with observations of Fe solubility in aerosol particles over the Bay of Bengal, due to the initial rapid release of Fe and the suppression of the oxalate-promoted dissolution at low pH. The improved model enabled us to predict sensitivity to a more dynamic range of pH changes, particularly between anthropogenic combustion and biomass burning aerosols.
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May 2022
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I18-Microfocus Spectroscopy
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Abstract: Benthonic fauna (earthworms, nematodes) are widely studied species in soil ecotoxicology due to their strong metal accumulation ability and potential role in terrestrial ecosystems. Study of toxic metal(loid)s behavior in benthonic fauna such as earthworms, which inhabit contaminated soils and sediments, has great significance in ecotoxicological research. This chapter reviews the uses and applications of microprobe-X-ray fluorescence to analyze toxic metal(loid)s and their distribution in benthonic fauna species including sample preparation methods and analytical conditions. The following two methods can retain the original structure of the samples: sample preparation for dehydration; and sample preparation for hydration. The chapter provides an overview of achievements in toxic elements imaging and elaborated the accumulation and storage mechanism of heavy metals through insights into distribution characteristics and behavior of toxic elements present in these species. The application areas of benthic organisms can be significantly broadened, with viable uses in phytoremediation and ecological risk assessment using microprobe-XRF imaging techniques.
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Apr 2022
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[16025]
Open Access
Abstract: Assessing element speciation and solubility control mechanisms in multi-contaminated soils poses great challenges. In this study, we examined the speciation and mechanisms controlling the solubility of As and Zn in a soil historically contaminated with As, Cu, Cr, and Zn salts used for wood preservation. The leaching behavior of dissolved species, particles, and colloids was studied in an irrigation experiment with intact soil columns. Batch experiments were used to study the solubility of dissolved species as a function of pH (2–8). The speciation of As and Zn in bulk soil and leached particles was studied with microscale X-ray fluorescence (μ-XRF) and extended X-ray absorption fine structure (EXAFS) spectroscopy. Chemical speciation and solubility were evaluated by geochemical modelling. μ-XRF of bulk soil and particles showed that As and Zn were correlated in space. Bulk- and μ-EXAFS of As and Zn, in combination with calculated ion activity products of possible As-Zn minerals, suggested a koritnigite (ZnHAsO4·H2O) phase controlling the dissolved fraction of As(V) and Zn with an apparent log Ksp of −21.9 ± 0.46. This phase lowered the solubility of As by almost two orders of magnitude in soil at pH > 5, and could therefore be of great importance at other multi-contaminated sites.
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Apr 2022
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I18-Microfocus Spectroscopy
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Sarah
Gosling
,
Doriana
Calabrese
,
Jayakrupakar
Nallala
,
Charlene
Greenwood
,
Sarah
Pinder
,
Lorraine
King
,
Jeffrey
Marks
,
Donna
Pinto
,
Thomas
Lynch
,
Iain D.
Lyburn
,
E. Shelley
Hwang
,
Cruk
Grand Challenge Precision Consortium
,
Keith
Rogers
,
Nicholas
Stone
Diamond Proposal Number(s):
[21565, 25414, 27300]
Open Access
Abstract: Ductal carcinoma in situ (DCIS) is frequently associated with breast calcification. This study combines
multiple analytical techniques to investigate the heterogeneity of these calcifications at the micrometre
scale. X-ray diffraction, scanning electron microscopy and Raman and Fourier-transform infrared spectroscopy were used to determine the physicochemical and crystallographic properties of type II breast calcifications located in formalin fixed paraffin embedded DCIS breast tissue samples. Multiple calcium phosphate phases were identified across the calcifications, distributed in different patterns. Hydroxyapatite was
the dominant mineral, with magnesium whitlockite found at the calcification edge. Amorphous calcium
phosphate and octacalcium phosphate were also identified close to the calcification edge at the apparent
mineral/matrix barrier. Crystallographic features of hydroxyapatite also varied across the calcifications, with
higher crystallinity centrally, and highest carbonate substitution at the calcification edge. Protein was also
differentially distributed across the calcification and the surrounding soft tissue, with collagen and β-pleated
protein features present to differing extents. Combination of analytical techniques in this study was essential
to understand the heterogeneity of breast calcifications and how this may link crystallographic and physicochemical properties of calcifications to the surrounding tissue microenvironment.
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Mar 2022
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I14-Hard X-ray Nanoprobe
I18-Microfocus Spectroscopy
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Abstract: New mineralogical studies of Lafayette reveal that it contains a notably variable abundance of martian carbonate. Four percent was identified in mesostasis (3.2%) and olivine-hosted (0.8%) fractures in one polished section, but only 0.2% of both textural types in another. The Lafayette carbonates are Mg0.0-2.0Cc13.2-38.6Sd17.7-81.9Rh3.1-42.9. They have undergone variable but extensive amounts of dissolution and replacement as the nakhlite secondary fluid evolved, associated with the precipitation of ferric saponite in olivine fractures and a serpentine-like phyllosilicate in the mesostasis. The mesostasis carbonate has undergone the highest degree of corrosion and replacement. TEM analysis has shown the presence of Fe-(hydr)oxide (likely ferrihydrite) nanoparticles on olivine-hosted carbonates which can be linked to the cessation of more extensive carbonate dissolution at those sites. The mesostasis serpentine-like mineral has been described here on the basis of WDS and EDX analyses, HRTEM and Fe-K XANES, as odinite, a ferric, 0.7 nm d001-spacings phyllosilicate mineral with a characteristic 1:1 serpentine-like structure. The carbonate dissolution stage and then formation of Fe-(hydr)oxide nanoparticles occurred under circumneutral-alkaline conditions 7 < pH < 10. This range of pH is also where the general dissolution mechanism switched from a proton-promoted, to a water hydrolysis reaction associated with a reduction in the dissolution rates. As dissolution rates were reduced and the fluid had cooled to ≤50°C, the precipitation of the ferric saponite and odinite, a phyllosilicate associated with temperatures of ∼25°C, dominated over the carbonate dissolution. The extensive dissolution of such crustal carbonate across the upper martian crust, producing bicarbonate and carbon dioxide, and the coupled formation of ferric phyllosilicates, would lead to the formation of CH4 in substantial amounts via a Fischer-Tropsch type reaction. The results of our study illustrate a process to explain the relatively low abundance of detected carbonate on Mars and a likely source for some of the methane on Mars.
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Feb 2022
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I13-2-Diamond Manchester Imaging
I18-Microfocus Spectroscopy
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Sam
Keyes
,
Arjen
Van Veelen
,
Dan
Mckay Fletcher
,
Callum
Scotson
,
Nico
Koebernick
,
Chiara
Petroselli
,
Katherine
Williams
,
Siul
Ruiz
,
Laura
Cooper
,
Robbie
Mayon
,
Simon
Duncan
,
Marc
Dumont
,
Iver
Jakobsen
,
Giles
Oldroyd
,
Andrzej
Tkacz
,
Philip
Poole
,
Fred
Mosselmans
,
Camelia
Borca
,
Thomas
Huthwelker
,
David L.
Jones
,
Tiina
Roose
Open Access
Abstract: Phosphorus (P) is essential for plant growth. Arbuscular mycorrhizal fungi (AMF) aid its uptake by acquiring sources distant from roots in return for carbon. Little is known about how AMF colonise soil pore-space, and models of AMF-enhanced P-uptake are poorly validated. We used synchrotron X-ray computed tomography (SXRCT) to visualize mycorrhizas in soil, and synchrotron X-ray fluorescence (XRF/XANES) elemental mapping for phosphorus (P), sulphur (S) and aluminium (Al), in combination with modelling. We found that AMF inoculation had a suppressive effect on colonisation by other soil fungi and identified differences in structure and growth rate between hyphae of AMF and nonmycorrhizal fungi. Results showed that AMF co-locate with areas of high P and low Al, andpreferentially associate with organic-type P species in preference to Al-rich inorganic P. We discovered that AMF avoid Al-rich areas as a source of P. S-rich regions correlated with higher hyphal density and an increased organic-associated P-pool, whilst oxidized S-species were found close to AMF hyphae. Increased S oxidation close to AMF suggested the observed changes were microbiome-related. Our experimentally-validated model led to an estimate of P-uptake by AMF hyphae that is an order of magnitude lower than rates previously estimated; a result with significant implications for modelling of plant-soil-AMF interactions.
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Jan 2022
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[4940]
Open Access
Abstract: In order to provide important details concerning the adsorption reactions of Sr, batch reactions and a set of both ex situ and in situ Grazing Incidence X-ray Absorption Fine Structure (GIXAFS) adsorption experiments were completed on powdered TiO2 and on rutile(110), both reacted with either SrCl2 or SrCO3 solutions. TiO2 sorption capacity for strontium (Sr) ranges from 550 ppm (SrCl2 solutions, second order kinetics) to 1400 ppm (SrCO3 solutions, first order kinetics), respectively, and is rapid. Sr adsorption decreased as a function of chloride concentration but significantly increased as carbonate concentrations increased. In the presence of carbonate, the ability of TiO2 to remove Sr from the solution increases by a factor of ~4 due to rapid epitaxial surface precipitation of an SrCO3 thin film, which registers itself on the rutile(110) surface as a strontianite-like phase (d-spacing 2.8 Å). Extended X-ray Absorption Fine Structure (EXAFS) results suggest the initial attachment is via tetradental inner-sphere Sr adsorption. Moreover, adsorbates from concentrated SrCl2 solutions contain carbonate and hydroxyl species, which results in both inner- and outer-sphere adsorbates and explains the reduced Sr adsorption in these systems. These results not only provide new insights into Sr kinetics and adsorption on TiO2 but also provide valuable information concerning potential improvements in effluent water treatment models and are pertinent in developing treatment methods for rutile-coated structural materials within nuclear power plants.
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Dec 2021
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I14-Hard X-ray Nanoprobe
I18-Microfocus Spectroscopy
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Abstract: This thesis focuses on the mineralogical study of altered martian meteorites and the development of a novel wet-chemistry instrument. X-ray spectroscopy and electron microscopy have been used to investigate the secondary mineralogy of martian meteorites and their associated fluids. Martian analogue brines were investigated with transmission spectroscopy in order to address the technique’s capabilities for detecting dilute, astrobiologically significant fluids.
The newly-found martian shergottite, Northwest Africa (NWA) 10416, bears a distinctive colouration in its olivine megacrysts which is suggestive of hydrous alteration. The meteorite has been petrographically characterised and the origin of its alteration has been determined as terrestrial. Oxygen isotope analysis and the observation of secondary phases within shock features using Transmission Electron Microscopy (TEM) have indicated a terrestrial fluid. Synchrotron X-ray Absorption Spectroscopy (XAS), X-ray Diffraction (XRD) and Electron Probe Micro-Analysis (EPMA) have allowed its characterisation as a low-temperature, possibly acidic, fluid.
Analysis of the martian nakhlite, Lafayette, has been performed in order to assess the extent of carbonate dissolution by a hydrothermal martian fluid. Textures determined by Scanning Electron Microscopy (SEM) and TEM, and compositions determined by EPMA and XAS have displayed the variable nature of this dissolution and allowed the identification of the mesostasis phyllosilicate as odinite. This work has illustrated a process in which martian crustal fluids can dissolve carbonates and produce substantial amounts of methane, informing our understanding of martian atmospheric methane.
The capabilities of transmission spectroscopy when detecting organic martian analogue brines have been assessed to further the development of the wet-chemistry instrument, ASPIRE. Transmission spectroscopy was unsuccessful in detecting the likely low organic concentrations (ppb) expected in potentially habitable martian aqueous environments. However, future avenues of research have been suggested for consideration, including investigation into the potential of reflectance spectroscopy and calibration of ASPIRE to mineralogical-free regions within the infrared region.
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Dec 2021
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I18-Microfocus Spectroscopy
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Open Access
Abstract: Portlandite [Ca(OH)2] is a potentially dominant solid phase in the high pH fluids expected within the cementitious engineered barriers of Geological Disposal Facilities (GDF). This study combined X-ray Absorption Spectroscopy with computational modelling in order to provide atomic-scale data which improves our understanding of how a critically important radionuclide (U) will be adsorbed onto this phase under conditions relevant to a GDF environment. Such data are fundamental for predicting radionuclide mass transfer. Surface coordination chemistry and speciation of uranium with portlandite [Ca(OH)2] under alkaline groundwater conditions (ca. pH 12) were determined by both in situ and ex situ grazing incidence extended X-ray absorption fine structure analysis (EXAFS) and by computational modelling at the atomic level. Free energies of sorption of aqueous uranyl hydroxides, [UO2(OH)n]2–n (n = 0–5) with the (001), (100) and (203) or (101) surfaces of portlandite are predicted from the potential of mean force using classical molecular umbrella sampling simulation methods and the structural interactions are further explored using fully periodic density functional theory computations. Although uranyl is predicted to only weakly adsorb to the (001) and (100) clean surfaces, there should be significantly stronger interactions with the (203/101) surface or at hydroxyl vacancies, both prevalent under groundwater conditions. The uranyl surface complex is typically found to include four equatorially coordinated hydroxyl ligands, forming an inner-sphere sorbate by direct interaction of a uranyl oxygen with surface calcium ions in both the (001) and (203/101) cases. In contrast, on the (100) surface, uranyl is sorbed with its axis more parallel to the surface plane. The EXAFS data are largely consistent with a surface structural layer or film similar to calcium uranate, but also show distinct uranyl characteristics, with the uranyl ion exhibiting the classic dioxygenyl oxygens at 1.8 Å and between four and five equatorial oxygen atoms at distances between 2.28 and 2.35 Å from the central U absorber. These experimental data are wholly consistent with the adsorbate configuration predicted by the computational models. These findings suggest that, under the strongly alkaline conditions of a cementitious backfill engineered barrier, there would be significant uptake of uranyl by portlandite to inhibit the mobility of U(VI) from the near field of a geological disposal facility.
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Nov 2021
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[24321]
Abstract: Looking for new green and environmentally friendly bio sorbents for metal removal from polluted wastewater, the present study investigates the potential new bio sorbent for Cd(II) removal from wastewater namely, the mechanism and uptake capacity of Cd(II) by brown algae, Fucus vesiculosus from the Irish Sea. This work takes a comprehensive approach involving the combination of qualitative and quantitative information collected from macro to atomistic scale, in a direct and non-destructive manner. Our results demonstrate that Cd(II) is adsorbed on the algal surface based on carboxylic of alginate groups. Effective Cd(II) adsorption is achieved at pH conditions between 5 and 7, at which the uptake occurs rapidly (∼2 h), with increasing Cd(II) concentration. Cd maximum uptake capacity (i.e., 1.203 mmol Cd g−1 dried algae) in first adsorption cycle show superior uptake as opposed to other species. Quantitatively the bio sorbent has an increasing uptake capacity (more than two folds) in the second cycle, after metal elution and biomass surface sites functioning. Desorption of Cd(II) and the regeneration of the biomass is effectively achieved with HCl (10 mM) and EDTA (1 mM), but they can only be used for two cycles, before the efficiency decreases. Microprecipitation occurs at high pH (>9) when using NaOH as an eluent. Results from this work shed new light on understanding Cd(II) binding mechanisms on Fucus v., providing crucial information for further process optimization, pilot testing, scaling up and implementation as a clean, environmentally friendly biotechnology applied to wastewater treatments.
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Oct 2021
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