I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[15971, 17888]
Abstract: Rhizosphere soil has distinct physical and chemical properties from bulk soil. However, besides root induced physical changes, chemical changes have not been extensively measured in situ on the pore scale.
In this study we couple structural information, previously obtained using synchrotron X‐ray computed tomography (XCT), with synchrotron X‐ray Fluorescence (SR‐XRF) microscopy and X‐ray Absorption Near‐Edge Structure (XANES) to unravel chemical changes induced by plant roots.
Our results suggest that iron (Fe) and sulfur (S) increase notably in the direct vicinity of the root via solubilization and microbial activity. XANES further shows that Fe is slightly reduced, S is increasingly transformed into sulfate (SO42‐) and that phosphorus (P) is increasable adsorbed to humic substances in this enrichment zone. In addition, the ferrihydrite fraction decreases drastically suggesting the preferential dissolution and the formation of more stable Fe‐oxides. Additionally, the increased transformation of organic S to sulfate indicates that the microbial activity in this zone is increased. These changes in soil chemistry correspond to the soil compaction zone as previously measured via X‐ray CT.
The fact that these changes are co‐located near the root and the compaction zone suggests that decreased permeability due to soil structural changes acts as a barrier creating a zone with increased rhizosphere chemical interactions via surface mediated processes, microbial activity and acidification.
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Oct 2019
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I18-Microfocus Spectroscopy
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Phillip L.
Manning
,
Nicholas P.
Edwards
,
Uwe
Bergmann
,
Jennifer
Anne
,
William
Sellers
,
Arjen
Van Veelen
,
Dimosthenis
Sokaras
,
Victoria M.
Egerton
,
Roberto
Alonso-mori
,
Konstantin
Ignatyev
,
Bart E.
Van Dongen
,
Kazumasa
Wakamatsu
,
Shosuke
Ito
,
Fabien
Knoll
,
Roy A.
Wogelius
Diamond Proposal Number(s):
[12948, 11865, 9488, 8597, 7749]
Open Access
Abstract: Recent progress has been made in paleontology with respect to resolving pigmentation in fossil material. Morphological identification of fossilized melanosomes has been one approach, while a second methodology using chemical imaging and spectroscopy has also provided critical information particularly concerning eumelanin (black pigment) residue. In this work we develop the chemical imaging methodology to show that organosulfur-Zn complexes are indicators of pheomelanin (red pigment) in extant and fossil soft tissue and that the mapping of these residual biochemical compounds can be used to restore melanin pigment distribution in a 3 million year old extinct mammal species (Apodemus atavus). Synchotron Rapid Scanning X-ray Fluorescence imaging showed that the distributions of Zn and organic S are correlated within this fossil fur just as in pheomelanin-rich modern integument. Furthermore, Zn coordination chemistry within this fossil fur is closely comparable to that determined from pheomelanin-rich fur and hair standards. The non-destructive methods presented here provide a protocol for detecting residual pheomelanin in precious specimens.
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May 2019
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[11412]
Open Access
Abstract: Neptunium and uranium are important radionuclides in many aspects of the nuclear fuel cycle and are often present in radioactive wastes which require long term management. Understanding the environmental behaviour and mobility of these actinides is essential in underpinning remediation strategies and safety assessments for wastes containing these radionuclides. By combining state-of-the-art X-ray techniques (synchrotron-based Grazing Incidence XAS, and XPS) with wet chemistry techniques (ICP-MS, liquid scintillation counting and UV-Vis spectroscopy), we determined that contrary to uranium(VI), neptunium(V) interaction with magnetite is not significantly affected by the presence of bicarbonate. Uranium interactions with a magnetite surface resulted in XAS and XPS signals dominated by surface complexes of U(VI), while neptunium on the surface of magnetite was dominated by Np(IV) species. UV-Vis spectroscopy on the aqueous Np(V) species before and after interaction with magnetite showed different speciation due to the presence of carbonate. Interestingly, in the presence of bicarbonate after equilibration with magnetite, an unknown aqueous NpO2+ species was detected using UV-Vis spectroscopy, which we postulate is a ternary complex of Np(V) with carbonate and (likely) an iron species. Regardless, the Np speciation in the aqueous phase (Np(V)) and on the magnetite (111) surfaces (Np(IV)) indicate that with and without bicarbonate the interaction of Np(V) with magnetite proceeds via a surface mediated reduction mechanism. Overall, the results presented highlight the differences between uranium and neptunium interaction with magnetite, and reaffirm the potential importance of bicarbonate present in the aqueous phase.
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Feb 2019
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I18-Microfocus Spectroscopy
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Jennifer
Anne
,
Roya A.
Wogelius
,
Nicholas P.
Edwards
,
Arjen
Van Veelen
,
Michael
Buckley
,
William
Sellers
,
Uwe
Bergmann
,
Dimosthenis
Sokaras
,
Roberto
Alonso-mori
,
Virginia L.
Harvey
,
Victoria M.
Egerton
,
Phillip L.
Manning
Diamond Proposal Number(s):
[9488]
Abstract: Trace element inventories are known to correlate with specific histological structures in bone, reflecting organismal physiology and life histories. By studying trace elements in fossilised bone, particularly in individuals with cyclic bone growth (alternating fast/slow bone deposition), we can improve our understanding of the physiology of extinct organisms. In this study we present the first direct comparison between optical histology (bone tissue identification) and synchrotron-based chemical mapping, quantification, and characterisation of trace elements (biochemistry) within cyclic growth tissues, in this case within bones of a cave hyaena (Crocuta crocuta spelaea). Results show distributions of zinc, an element strongly associated with active ossification and bone growth, correlating with (1) fast-growing tissue of zonal bone (cyclic growth) in an extinct hyaena and (2) secondary osteons (remodelling) in both extant and extinct hyaena. Concentrations and coordination chemistry of zinc within the fossil sample are comparable to those seen in extant bone suggesting that zinc is endogenous to the sample and that the chemistry of bone growth has been preserved for 40 ka. These results demonstrate that the study of trace elements as part of the histochemistry has wide utility for reconstructing growth, diet and other lifestyle factors in archaeological and fossil bone.
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Oct 2018
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B18-Core EXAFS
I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[11865]
Abstract: Endochondral ossification is the process by which bone is deposited during development, growth and repair of the skeleton. The regulation of endochondral ossification is extremely important as developmental flaws can result in severe skeletal abnormalities. However, until recently the limitations of available methodologies have restricted our understanding of this fundamental physiological process. The analysis of chemical elements that are intimately associated with discrete biochemical stages of ossification within bone could provide new insight to such processes at the atomic level. In this study we present detailed characterisation of the elemental inventory within actively ossifying bone during development in mice using synchrotron microfocus X-ray techniques. X-ray fluorescence imaging showed differential distributions of Zn, Sr and Ca, which may be correlated with the processes of cartilage replacement (Zn), active ossification (Sr) and fully ossified tissues (Ca). Quantification of these trace elements confirmed their relative distributions. These results represent the first detailed visualisation of local endochondral ossification processes using trace elemental mapping. Such studies have far reaching applications not only in the medical field, but to our understanding of the evolution of the bony skeleton given that trace element inventories have been shown to be preserved through deep time (millions of years).
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Mar 2017
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I18-Microfocus Spectroscopy
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Nicholas
Edwards
,
Arjen
Van Veelen
,
Jennifer
Anné
,
Phillip
Manning
,
Uwe
Bergmann
,
William
Sellers
,
Victoria
Egerton
,
Dimosthenis
Sokaras
,
Roberto
Alonso-mori
,
Kazumasa
Wakamatsu
,
Shosuke
Ito
,
Roy A.
Wogelius
Diamond Proposal Number(s):
[11865, 12948]
Open Access
Abstract: Melanin is a critical component of biological systems, but the exact chemistry of melanin is still imprecisely known. This is partly due to melanin’s complex heterogeneous nature and partly because many studies use synthetic analogues and/or pigments extracted from their natural biological setting, which may display important differences from endogenous pigments. Here we demonstrate how synchrotron X-ray analyses can non-destructively characterise the elements associated with melanin pigment in situ within extant feathers. Elemental imaging shows that the distributions of Ca, Cu and Zn are almost exclusively controlled by melanin pigment distribution. X-ray absorption spectroscopy demonstrates that the atomic coordination of zinc and sulfur is different within eumelanised regions compared to pheomelanised regions. This not only impacts our fundamental understanding of pigmentation in extant organisms but also provides a significant contribution to the evidence-based colour palette available for reconstructing the appearance of fossil organisms.
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Sep 2016
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[9488, 8597]
Open Access
Abstract: Bone remodelling is a crucial biological process needed to maintain elemental homeostasis. It is important to understand the trace elemental inventories that govern these processes as malfunctions in bone remodelling can have devastating effects on an organism. In this study, we use a combination of X-ray techniques to map, quantify, and characterise the coordination chemistry of trace elements within the highly remodelled bone tissues of extant and extinct Sirenia (manatees and dugongs). The dense bone structure and unique body chemistry of sirenians represent ideal tissues for studying both high remodelling rates as well as unique fossilisation pathways. Here, elemental maps revealed uncorrelated patterning of Ca and Zn within secondary osteons in both extant and fossil sirenians, as well as elevated Sr within the connecting canals of fossil sirenians. Concentrations of these elements are comparable between extant and fossil material indicating geochemical processing of the fossil bone has been minimal. Zn was found to be bound in the same coordination within the apatite structure in both extant and fossil bone. Accurate quantification of trace elements in extant material was only possible when the organic constituents of the bone were included. The comparable distributions, concentrations, and chemical coordination of these physiologically important trace elements indicate the chemistry of bone remodelling has been preserved for 19 million years. This study signifies the powerful potential of merging histological and chemical techniques in the understanding of physiological processes in both extant and extinct vertebrates.
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Mar 2016
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I18-Microfocus Spectroscopy
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Victoria
Egerton
,
R A
Wogelius
,
Mark A.
Norell
,
Nicholas
Edwards
,
William
Sellers
,
Uwe
Bergmann
,
Dimosthenis
Sokaras
,
Roberto
Alonso-mori
,
Konstantin
Ignatyev
,
Arjen
Van Veelen
,
Jennifer
Anné
,
Bart
Van Dongen
,
Fabien
Knoll
,
Phillip
Manning
Diamond Proposal Number(s):
[8597, 9488]
Open Access
Abstract: The preservation of fossils reflects the interplay of inorganic and organic chemical processes, which should be clearly differentiated to make interpretations about the biology of extinct organisms. A new coliiformes bird (mouse bird) from the [similar]50 million year old Green River Formation (Wyoming, USA) has here been analysed using synchrotron X-ray fluorescence and environmental scanning electron microscopy with an attached X-ray energy dispersive system (ESEM-EDS). The concentration and distribution of 16 elements (Si, P, S, Cl, K, Ca, Ti, Mg, Fe, Ni, Cu, Zn, As, Br, Ba, Hg) has been mapped for individual points on the sample. S, Cu and Zn map distinctly within visibly preserved feathers and X-ray Absorption Spectroscopy (XAS) shows that S and Cu within the feathers are organically bound in a similar manner to modern feathers. The morphological preservation of the feathers, on both macro- and microscopic scales, is variable throughout the fossil and the differences in the lateral microfacies have resulted in a morphological preservation gradient. This study clearly differentiates endogenous organic remains from those representing exogenous overprinted geochemical precipitates and illustrates the chemical complexity of the overall taphonomic process.
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Jan 2015
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I18-Microfocus Spectroscopy
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Diamond Proposal Number(s):
[8597]
Abstract: Many exceptionally preserved fossils have long been thought the product of preservation by bacterial autolithification, based largely upon the presence of, micron-sized, spherical or elongate bodies on their surface. This has recently been challenged by studies of similar fossils which cite morphological and geochemical evidence that these structures could be fossilized melanosomes, melanin-containing organelles. We geochemically analysed a tadpole from the Oligocene Enspel Formation, Germany, which displays such spherical bodies on its surface. Pyrolysis gas chromatography mass spectroscopy (Py-GCMS) and Fourier transform infrared spectrometry (FTIR) indicate that the organic remains of the tadpole are original and are not the result of external contamination, shown by the different chemical compositions of the fossil and its enclosing matrix. Py-GCMS also demonstrates the presence of bacterial and plant biomarkers in the matrix but not the tadpole, suggesting that the spherical bodies are unlikely to be bacterial, and also that such fossils do not develop their dark colour from incorporating plant material, as has been suggested. X-ray absorption spectroscopy (XAS) shows high levels of organically bound Zn(II) in the fossilized soft tissue, a metal known to chelate both eu- and pheomelanin. The zinc in the tadpole shows greater similarity to that bound in pheomelanized extant samples than to that in eumelanized ones. Though further geochemical analysis of both pure pheomelanin and bacterial samples is required to completely exclude a bacterial origin, these results are in line with a pheomelanic origin for the spherical bodies on the tadpole.
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Nov 2014
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B18-Core EXAFS
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Diamond Proposal Number(s):
[7799]
Abstract: Iron oxides resulting from the corrosion of large quantities of steel that are planned to be installed throughout a deep geological disposal facility (GDF) are expected to be one of the key surfaces of interest for controlling radionuclide behaviour under disposal conditions. Over the lengthy timescales associated with a GDF, the system is expected to become anoxic so that reduced Fe(II) phases will dominate. Batch experiments have therefore been completed in order to investigate how a model reduced Fe-oxide surface (wüstite, Fe1xO) alters as a function of exposure to aqueous solutions with compositions representative of conditions expected within a GDF. Additional experiments were performed to constrain the effect that highly alkaline solutions (up to pH 13) have on the adsorption behaviour of the uranyl (Formula ) ion onto the surfaces of both wüstite and portlandite [Ca(OH)2; representative of the expected cementitious phases]. Surface co-ordination chemistry and speciation were determined by ex situ X-ray absorption spectroscopy measurements (both X-ray absorption near-edge structure analysis (XANES) and extended X-ray absorption fine structure analysis (EXAFS)). Diffraction, elemental analysis and XANES showed that the bulk solid composition and Fe oxidation state remained relatively unaltered over the time frame of these experiments (120 h), although under alkaline conditions possible surface hydroxylation is observed, due presumably to the formation of surface hydroxyl complexes. The surface morphology, however, is altered significantly with a large degree of roughening and an observed decrease in the average particle size. Reduction of U(VI) to U(IV) occurs during adsorption in almost all cases and this is interpreted to indicate that wüstite may be an effective reductant of U during surface adsorption. This work also shows that increasing the carbonate concentration in reactant solutions dramatically decreases the adsorption coefficients for U on both wüstite and portlandite, consistent with U speciation and surface reactivity determined in other studies. Finally, the EXAFS results include new details about exactly how U bonds to this metal oxide surface.
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Nov 2014
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