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Abstract: Although oil and gas (O&G) derived produced waters and drill cuttings are known to contain enhanced levels of naturally occurring radium-228 (228Ra) and radium-226 (226Ra), most relevant ecological impact assessments have excluded radiological hazards and focus on other important contaminants, such as hydrocarbons and metals. Also, due to restricted access to the delimiting safety zone around operational O&G platforms, the few previous radioecological risk assessment studies have been conducted using seawater samples collected far from the main discharge point and applying default dilution and transfer factors to estimate concentrations of contaminants in biota. In this case study, sediment cores were collected close to a former O&G platform, Northwest Hutton (NWH), that used to be in the UK North Sea (61.11N, 1.31E). The sediment materials were analysed by gamma spectrometry and ICP-MS to confirm the presence of particles enriched in natural radioactivity. Benthic macrofaunal assemblages in the surrounding seabed were also characterised and one of the dominant species was selected for additional nano-hard X-Ray Fluorescence (nano-XRF) imaging to confirm the exposure pathways and refine the radioecological risk assessment using the ERICA tool. This novel approach for estimating dose rates was found to be less conservative than more traditional approaches using the ERICA default concentration ratio for 228Ra and 226Ra. The dose rate estimations were confirmed to be significantly lower than the ERICA screening level of 10μGy/h, in agreement with findings from previous studies.

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Abstract: Understanding the interactions between metal-based nanoparticles and biological systems in complex environments (e.g., the human body, soils, and marine settings) remains challenging, especially at the single-cell and nanoscale levels. Capturing the dynamics of these interactions, such as metal distribution, nanoparticle growth, or degradation, in their native state (in vivo) is particularly difficult. Here, we demonstrate the direct measurement of iron content in hydrated, magnetite-biomineralizing magnetotactic bacteria using synchrotron-based nanobeam–scanning X-ray fluorescence microscopy combined with a liquid cell environment. In addition to X-ray fluorescence imaging, we collected iron chemical speciation information from individual bacteria in liquid using X-ray absorption spectroscopy. To follow biomineralization in situ, we developed a microfluidic device to track magnetite nanoparticle formation over several hours under the X-ray beam. This approach highlights the potential of X-ray fluorescence microscopy in liquid cell setups to provide elemental and chemical insights into biological processes at the single-cell level. Combining X-ray nanobeam techniques with liquid cell devices will enable more “on-chip” experiments on metals in biological contexts to be conducted at the synchrotron.

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Abstract: One of the key parameters defining the healthy functioning of soil is its structure. The organization of mineral particles, organic matter (OM), water, and air into a complex matrix of soil aggregates plays a particularly important role in long-term carbon (C) storage, as C compounds can be ‘hidden’ within the aggregate structure, shielding them from decomposers. Soil aggregation is a dynamic process influenced by physical, chemical, and biological factors; however, the individual and combined effects of these factors on the formation and turnover of aggregates are not well understood. The aim of this study was to examine the incorporation of fresh litter inputs with differing physicochemical properties, including their carbon-to-nitrogen (C/N) ratio—maize (C/N = 12) and straw (C/N = 103)—into aggregates formed de novo from mineral soil, with or without the presence of microbiota. Using rare-earth element oxides, we labeled structures formed during a four-week incubation with a single litter type and traced their incorporation into newly formed aggregates after mixing the soils and incubating them for a subsequent seven-week period. We found that, regardless of quality, litter was the most important factor driving soil aggregation during the initial stages of the process. The presence of both litter types together further enhanced aggregate formation. Contrary to our hypothesis, and likely due to the short time frame of the experiment, neither microbial abundance nor community composition significantly affected overall aggregation. However, further visualization of the different litter-associated structures across the cross-sections of the aggregates from various size fractions using synchrotron radiation-based X-ray fluorescence nanospectroscopy (SR-nanoXRF) enabled us to estimate potential influence of the microbes via their preferred litter type. Specifically, contrary to our expectations the bulk analysis showed that bacteria-favoured low C/N ratio maize litter had a stronger effect on both overall aggregation and the formation of macroaggregates, which we initially hypothesized would be supported by the high C/N ratio straw litter preferred by fungi. However, further analysis of the XRF intensity maps confirmed an increasing incorporation of straw-associated soils into >250 μm structures, likely facilitated by fungal growth and hyphal enmeshing. Phospholipid fatty acid analysis further corroborated this, showing a relatively higher abundance of fungi in macroaggregates in straw-containing soil. We also implemented semi-variogram analysis on the XRF maps, which allowed us to estimate the size and distribution of straw- and maize-associated structures within the aggregates. We found that while microaggregates were more commonly formed from individual litter-associated structures, larger aggregates (> 250 μm) were newly made from de-aggregated soil. In conclusion, our study provides insights into the initial stages of aggregate formation following litter additions and the development of associated microbial communities. The spatial analysis enabled by SR-nanoXRF allowed us to visualize internal aggregate structures, shedding light on processes that cannot be fully understood through bulk analysis alone.

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Abstract: Long-standing challenges including notorious side reactions at the Zn anode, low Zn anode utilization, and rapid cathode degradation at low current densities hinder the advancement of aqueous zinc-ion batteries (AZIBs). Inspired by the critical role of capping agents in nanomaterials synthesis and bulk crystal growth, a series of capping agents are employed to demonstrate their applicability in AZIBs. Here, it is shown that the preferential adsorption of capping agents on different Zn crystal planes, coordination between capping agents and Zn2+ ions, and interactions with metal oxide cathodes enable preferred Zn (002) deposition, water-deficient Zn2+ ion solvation structure, and a dynamic cathode-electrolyte interface. Benefiting from the multi-functional role of capping agents, dendrite-free Zn plating and stripping with an improved Coulombic efficiency of 99.2% and enhanced long-term cycling stability are realized. Remarkable capacity retention of 91% is achieved for cathodes after more than 500 cycles under a low current density of 200 mA g−1, marking one of the best cycling stabilities to date. This work provides a proof-of-concept of capping agents in manipulating electrochemical behaviors, which should inspire and pave a new avenue of research to address the challenges in practical energy storage beyond AZIBs.

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Abstract: Magnesium (Mg) – based alloys are becoming attractive materials for medical applications as temporary bone implants for support of fracture healing, e.g. as a suture anchor. Due to their mechanical properties and biocompatibility, they may replace titanium or stainless-steel implants, commonly used in orthopedic field. Nevertheless, patient safety has to be assured by finding a long-term balance between metal degradation, osseointegration, bone ultrastructure adaptation and element distribution in organs. In order to determine the implant behavior and its influence on bone and tissues, we investigated two Mg alloys with gadolinium contents of 5 and 10 wt percent in comparison to permanent materials titanium and polyether ether ketone. The implants were present in rat tibia for 10, 20 and 32 weeks before sacrifice of the animal. Synchrotron radiation-based micro computed tomography enables the distinction of features like residual metal, degradation layer and bone structure. Additionally, X-ray diffraction and X-ray fluorescence yield information on parameters describing the bone ultrastructure and elemental composition at the bone-to-implant interface. Finally, with element specific mass spectrometry, the elements and their accumulation in the main organs and tissues are traced. The results show that Mg-xGd implants degrade in vivo under the formation of a stable degradation layer with bone remodeling similar to that of Ti after 10 weeks. No accumulation of Mg and Gd was observed in selected organs, except for the interfacial bone after 8 months of healing. Thus, we confirm that Mg-5Gd and Mg-10Gd are suitable material choices for bone implants.