B18-Core EXAFS
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Diamond Proposal Number(s):
[37736]
Open Access
Abstract: 99Tc is a long-lived radioactive fission product whose subsurface mobility is governed by redox conditions. Under oxic conditions, soluble Tc(VII)O4– is mobile, whereas under reducing conditions, poorly soluble Tc(IV) phases limit transport. Microcosm studies have frequently reported TcO2-like solids and, less consistently, Tc(IV)-sulfides. The stability of Tc(IV)-sulfides under environmentally relevant conditions remains unclear. Here, we used flowing sediment columns representative of the Sellafield subsurface to examine Tc speciation and stability over ∼1 year. Under reducing conditions, >90% of added TcO4– (400 μg) was retained under both Fe(III)- and sulfate-reducing conditions. X-ray absorption spectroscopy showed TcO2-like phases dominated in Fe(III)-reducing columns, while Tc(IV)-sulfides dominated after sustained sulfate reduction. Sequential extractions indicated that Tc in sulfidic sediments was more recalcitrant (≤23% released by weak acids) than in Fe(III)-reducing systems (∼60% released). With oxic groundwater pumping, effluent Tc sourced from the sediments rose rapidly. Over 160 days, the sulfidic columns remobilized ∼25% of their Tc inventory compared to ∼50% in Fe(III)-reducing columns. The Tc(IV)-sulfides also gradually oxidized to form TcO2 phases. While Tc(IV)-sulfides may enhance Tc retention under reducing conditions, TcO2 phases more likely govern 99Tc mobility during long-term redox cycling. Our findings provide new constraints for modeling Tc fate at contaminated sites and in radioactive waste disposal.
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Dec 2025
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Open Access
Abstract: In recent years, elevated concentrations of arsenic (As) have been detected in the Tertiary detrital aquifer of Madrid. A significant number of areas where waste from old mining operations, rich in metals and metalloids, accumulate may partially explain contamination events by toxic elements. In these environments, colloidal particles can act as nanovectors for the dispersion of As, enhancing its migration and contamination of surrounding soils. This work studies the mobilization of As-rich colloids from a waste zone of an old mining operation in the Community of Madrid. These wastes, mainly composed of arsenopyrite [FeAsS] ([As] = 0.2 g kg-1), are deposited near a natural stream and exposed to environmental conditions. In order to follow the mobility of As-rich colloids, the combined techniques of asymmetric flow field flow fractionation and inductively coupled plasma mass spectrometry (AF4-ICP-MS) are used to obtain the size distribution of the colloidal fraction and associated As, while X-ray absorption spectroscopy (XAS) techniques are utilized for the study of the chemical speciation of As in the solid phase. In addition, geochemical modeling allows prediction of the thermodynamically favored phases in each of the studied areas. The mobilization of colloidal As from mining waste to water and soil located up to 1 km from the source of contamination is described. The essential role of colloidal Fe oxyhydroxides as As mobilizing nanovectors is also highlighted.
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Dec 2025
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I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[21441, 18594]
Abstract: Vanadium (V) is a widespread trace element in the environment. At high concentration, due to anthropogenic emission such as mining activities and fossil fuels, it can be toxic to marine systems and terrestrial plants. However, the geochemical behaviour of V remains poorly understood. Here, this study aimed to understand the molecular scale V speciation, adsorption behaviour and bonding mechanisms of V(V) onto hematite as a function of geochemical factors (pH, ionic strength, and V(V) concentration), applying a multi-technique approach comprising aqueous chemical analysis and XAS supported by ATR-FTIR and PHREEQC geochemical speciation calculations. From these data, tetrahedral monovanadate formed a corner-sharing bidentate surface complex at 1.20 mM V(V) and pH 9 and 0.12 mM V(V) at all pH, while octahedral decavanadate formed at a V(V) concentration of 1.20 mM and pH < 7. The dominant coordination environment changed gradually from a mixture of octahedrally and tetrahedrally coordinated V at pH 3 to tetrahedral monovanadate at pH 9. These results demonstrate the marked effects of pH and initial V concentration on V(V) speciation at hematite surfaces, in turn affording predictions of the environmental behaviour of heavy metals released during a variety of anthropogenic activities (e.g. mining) across a range of geochemical conditions. It is envisioned these results will contribute to strategies for the treatment of lands contaminated with heavy metals predominantly through adsorption processes (e.g. mine sites).
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Dec 2025
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Abstract: To address concerns about the ever-increasing release of photocatalytic engineered cerium oxide nanoparticles (nCeO2) into freshwaters, field experiments were conducted to evaluate their impacts on diatom-dominated assemblages of phytoplankton and phytobenthos from UK streams. Outcomes were compared to those obtained in laboratory toxicity tests on the freshwater diatom Fistulifera pelliculosa. Exposure to an environmentally relevant concentration (0.05 mg/L nCeO2) led to two significant stimulatory responses in photosynthetic performance, averaging ~15%, in phytobenthos, compared to a single minor inhibitory response (~7%) in phytoplankton, relative to controls. At supra-environmental exposures (5.0 mg/L nCeO2) two significant inhibitory responses (~13%) were measured in photosynthetic performance, in phytoplankton and only one (~11%) for phytobenthos, relative to controls. No significant impacts were detected in the benthic diatom Fistulifera pelliculosa at the same two concentrations, their release of copious extracellular polymeric substances likely reduced direct contact with nCeO2. Many diatoms contribute to the pool of natural organic matter in aquatic ecosystems through release extracellular polymeric substances (EPS). Phytobenthic cells embedded in the EPS matrix, may have received less exposure to nCeO2 than the phytoplankton. We consider the extent to which media-dependent nanoparticle characteristics and behaviour, including Ce3+/Ce4+ ratios, zeta-potential, hydrodynamic diameter, the polydispersity index, nanoparticle stabilisation and nanoparticle settlement may account for the observed differences. We propose that EPS-secreting diatoms would make ideal model species for future laboratory toxicity testing of newly emerging nanoparticle sub-types, as they generate environmentally realistic conditions, in artificial culture media, more closely representing those experienced by natural assemblages of phytoplankton and phytobenthos.
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Nov 2025
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B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS
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Diamond Proposal Number(s):
[33415, 34976]
Open Access
Abstract: Electro-oxidation is one of the most promising and eco-friendly technologies for water decontamination. However, its industrial application is still limited by the high cost, poor faradaic efficiency, low durability, and potential toxicity of common high-power oxidation anodes. These challenges have been addressed by developing a novel composite comprising a mixed metal oxide (NiMnO3) and reduced graphene oxide (rGO). The NiMnO3–rGO anode allowed the fast and complete removal of phenol. Among different highly porous substrates, graphite felt (GF) led to the highest energy efficiency, since the GF/NiMnO3–rGO anode yielded 100% phenol removal within only 30 min at a current density as low as 10 mA cm−2, which was accompanied by 85% COD removal at 120 min. This anode demonstrated excellent stability, maintaining 100% phenol removal efficiency across five consecutive cycles while also showing low energy consumption (60–65 Wh (kg COD)−1). Operando X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) analysis provided mechanistic insights. It is demonstrated that rGO shifts the ˙OH production pathway towards the lattice oxygen mechanism (LOM), in contrast to the adsorbate evolution mechanism (AEM) observed for NiMnO3 alone. This mechanistic shift supports the enhanced stability and sustained electrocatalytic activity, contributing to the high performance of the GF/NiMnO3–rGO composite anode in the context of a more sustainable technology for treating organic contaminants.
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Oct 2025
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I18-Microfocus Spectroscopy
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Ian T.
Burke
,
Patrizia
Onnis
,
Alex L.
Riley
,
Catherine J.
Gandy
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Violeta
Ramos
,
Gavyn K.
Rollinson
,
Patrick
Byrne
,
Richard A.
Crane
,
Karen A.
Hudson-Edwards
,
Elin
Jennings
,
William M.
Mayes
,
J. Frederick W.
Mosselmans
,
Adam P.
Jarvis
Diamond Proposal Number(s):
[29808, 31675]
Open Access
Abstract: The erosion of legacy coastal municipal solid waste landfill sites will result in the dispersion of particulate material into nearby ecosystems with potential for effects on marine populations. Information on the speciation and solid phase associations of metal(loid) contaminants will help to predict contaminant behaviour and better understand ecosystem risks. Here, we investigate the solid phase composition of, and metal(loid) leaching from, fine fraction materials recovered from three actively eroding coastal landfill sites. High concentrations of a range of potentially toxic elements (As, Cd, Cr, Cu, Pb, Ni and Zn) were present in multiple samples, but metal(loid) leaching rates were very low (≪1 wt%) in both deionised water and seawater solutions. Therefore, particulate dispersion is the most likely mode of contaminant transport occurring at these sites. The fine fraction materials were dominated by fine sand sized (63–180 μm) quartz grains and silt sized (<63 μm) matrix components, which were likely to be poorly retained on beaches and easily transported offshore. Four priority contaminants (As, Cu, Pb and Zn) were found to occur primarily in adsorbed or precipitate forms, as either coatings on other particles or as discrete <10 μm particles. Dilution of these fine-grained contaminated particles within natural pelitic sediments will likely reduce the overall ecosystems impacts; but the risks to filter and bottom feeding organisms, and the potential for biomagnification across trophic levels are poorly understood.
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Oct 2025
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I22-Small angle scattering & Diffraction
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María Calles
García
,
Hugo
Salazar
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Sylvia
Britto
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Oleksandr
Tomchuk
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Pedro M.
Martins
,
Arunava
Pradhan
,
Fernanda
Cássio
,
Senentxu Lanceros
Mendez
,
Koro
De La Caba
,
Pedro
Guerrero
,
Viktor
Petrenko
,
Roberto Fernández
De Luis
Diamond Proposal Number(s):
[42059]
Open Access
Abstract: Access to clean water in isolated regions remains a major challenge, particularly due to contamination by the five most prevalent heavy metals: Hg(II), Pb(II), Cd(II), As(III/V), and Cr(VI). Traditional sorbents are limited in their ability to capture all the “big five” heavy metals, since they occur as cationic, neutral, or anionic species under standard conditions. To address this challenge, we have integrated a thiol rich Zr(IV)- Metal-Organic Framework (MOF), namely BCM-1, into a soy protein (SPI) and chitin (CHI) sponge in order to engineer a 3D-hybrid water filter. The components and the composite systems were thoroughly characterised by conventional means. Additionally, neutron imaging was used to reveal the 3D-interconnected micro- to macroporous structure of the filters, while Small-Angle X-ray Scattering (SAXS) confirmed the presence of BCM-1 as monodisperse nanoparticles. The 3D-sponge combines mechanical stability, high permeability, and broad chemical affinity, allowing the efficient removal of all five heavy metals through simple adjustments of its activation conditions. Adsorption experiments demonstrated over 90 % removal for most target metals depending if the hybrid-sponge is employed as synthesised, or after activating at pH = 1. When tested with 1 ppm solutions, they exhibit adsorption efficiencies for Hg(II), Pb(II), Cd(II), As(V), and Cr(VI) of 60.8/100 %, 94.4/74.8 %, 15.7/69.1 %, 100/38.2 %, 5.7/100 %, and 13.5/97.4 %, before and after the activation of the 3D-sponge, respectively. The metrics are consistently maintained over three adsorption/desorption cycles in surface water samples. On the whole, this work provides a scalable and sustainable approach to combine biopolymers and MOFs for real-world water remediation applications and highlights the key role of their protonation state on their absorptive properties.
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Oct 2025
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I15-1-X-ray Pair Distribution Function (XPDF)
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Diamond Proposal Number(s):
[34797]
Open Access
Abstract: MOF@COF composites have emerged as a promising class of engineered materials with unique functionalities, combining the high porosity and tunability of metal-organic frameworks (MOFs) with the chemical and mechanical stability of covalent-organic frameworks (COFs). While their advantageous properties are well-recognized, their structural intricacies and the nature of the interfacial interactions remain insufficiently explored. In this study, a Fe-MOF@COF composite is presented, exhibiting dual functionalities for the efficient removal of organic pollutants from water. The enhanced performance is attributed to the unique properties of the MOF-COF interface, where synergistic interactions between the two porous materials play a critical role. Advanced synchrotron techniques were employed to probe interfacial interactions at the atomic and molecular levels. These findings underscore the potential of Fe-MOF@COF composite as a highly effective material for water remediation, providing deeper insights into their structural behavior and interfacial properties.
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Aug 2025
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B18-Core EXAFS
I14-Hard X-ray Nanoprobe
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You Cheng
Khng
,
Gianni F.
Vettese
,
Satoshi
Utsunomiya
,
Joyce W. L.
Ang
,
Jessica M.
Walker
,
Julia
Parker
,
Thomas
Neil
,
Katherine
Morris
,
Liam
Abrahamsen-Mills
,
Mirkka
Sarparanta
,
Gareth T. W.
Law
Diamond Proposal Number(s):
[31916, 31395]
Open Access
Abstract: Uranium dioxide (UO₂) particles can be released from mines, nuclear fuel manufacturing, reactor accidents, and weapons use. They pose inhalation risks, yet their behavior in the human lung remains poorly understood. This study investigates the long-term chemical alteration and dissolution of µm-sized UO₂ particles in two model lung fluids: Simulated Lung Fluid (SLF) and Artificial Lysosomal Fluid (ALF), representing extracellular and intracellular lung environments, respectively. Particles were exposed to each fluid at 37°C for up to 180 days (SLF) and 900 days (ALF). In SLF, UO₂ showed low apparent solubility (<2% U released to solution), but solid-phase analyses revealed significant oxidation of U(IV) (~50%) and formation of autunite-like sheets on the UO2 surface. Secondary phase formation may lessen overall UO2 dissolution, promoting long-term particle retention, whilst modifying particle chemical toxicity and cell uptake. In contrast, Monte Carlo simulations indicate that the SLF-induced surface alteration would reduce (>50%) external radiation dose from the particles. In contrast, UO₂ readily dissolved in ALF (~75% uranium released to solution in 60 days, ~100% by 900 days). There was no evidence of secondary phase formation in ALF, but extensive particle matrix dissolution/disaggregation was observed by 30 days. Fragmentation of the UO2 polycrystalline matrix may lead to release of smaller UO₂ crystallites, which could translocate more readily. Overall, this work provides new mechanistic insight into the fate of inhaled UO₂ under physiologically relevant conditions, highlighting a possible need to consider particle reactivity and alteration processes in health risk assessments.
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Aug 2025
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B18-Core EXAFS
I14-Hard X-ray Nanoprobe
I20-Scanning-X-ray spectroscopy (XAS/XES)
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Diamond Proposal Number(s):
[25930, 24074, 21441]
Open Access
Abstract: Uranium (U) is a natural radioactive metal and a persistent environmental pollutant. Characterising the influence of arbuscular mycorrhizal fungi (AMF) on U bioaccumulation and partitioning in plants is crucial to understand U soil-to-plant transfer mechanisms. High resolution elemental mapping, spectroscopy and microscopy techniques were conducted on uranyl nitrate dosed Plantago lanceolata roots colonised with Rhizophagus irregularis. U-rich particles accumulated within the root cells, with higher abundance in epidermal and outer cortex cells of mycorrhizal root samples than in non-mycorrhizal roots. Electron microscopy determined two different crystalline U phases, an acicular crystal and a novel rounded aggregate formation, the latter of which was only found within the mycorrhizal root cells. Multiple imaging and spectroscopic techniques enabled the dominant elements with these U biominerals to be determined. Co-localisation between U, phosphorus and oxygen indicated the dominance of U-phosphate biominerals, but metals including calcium and zinc were also found to co-localise. The most dominant U compound was uranyl orthophosphate, likely accompanied by autunite. This study demonstrates alteration in U localisation and U particle morphology within Plantago roots as a direct consequence of AMF colonisation. This knowledge will allow more accurate U food-chain transfer modelling and better assessment of AMF-assisted phytoremediation feasibility.
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Jun 2025
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