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Browsing by Author "Howard, DL"

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Biofilm-enhanced adsorption of strong and weak cations onto different microplastic sample types: use of spectroscopy, microscopy and radiotracer methods
(Elsevier, 2019-07-01) Johansen, MP; Cresswell, T; Davis, J; Howard, DL; Howell, NR; Prentice, E
The adsorption of metals and other elements onto environmental plastics has been previously quantified and is known to be enhanced by surface-weathering and development of biofilms. However, further biofilm-adsorption characterisation is needed with respect to the fate of radionuclides. This study uses spectroscopy, microscopy and radiotracer methods to investigate the adsorption capacity of relatively strong and weak cations onto different microplastic sample types that were conditioned in freshwater, estuarine and marine conditions although marine data were limited. Fourier-transform infrared spectroscopy confirmed that surface oxidation chemistry changes induced by gamma irradiation were similar to those resulting from environmental exposures. Microscopy elemental mapping revealed patchy biofilm development, which contained Si, Al, and O, consistent with microbial-facilitated capture of clays. The plastics+biofilm of all sample types had measurable adsorption for Cs and Sr radiotracers, suggesting environmental plastics act broadly as a sink for the key pervasive environmental radionuclides of 137Cs and 90Sr associated with releases from nuclear activities. Adsorption onto high-density polyethylene plastic types was greater than that on polypropylene. However, in most cases, the adsorption rates of all types of plastic+biofilm were much lower than those of reference sediments and roughly consistent with their relative exchangeable surface areas. Crown Copyright © 2019 Published by Elsevier Ltd.
Characterisation of anthropogenic radioactive particles from former weapon test sites in Australia
(South Pacific Environmental Radioactivity Association, 2018-11-06) Young, EL; Johansen, MP; Child, DP; Hotchkis, MAC; Howell, NR; Pastuovic, Z; Howard, DL; Palmer, T; Davis, J
Former nuclear test sites on Australian territories such as those at Maralinga and the Montebello islands have been remediated to varying extents but wide-spread radioactivity still remains. Fission and neutron-activation products at the test sites have been decaying over time but long-lived radioisotopes such as uranium and plutonium persist within the environment, predominantly in the form of discrete particles. These particles vary widely in composition depending upon the detonation characteristics and local geology, and are widely dispersed around each site. Radioactive particles are the dominant form of radionuclides at the former test sites and the future distribution of radioactive contaminants in the environment at these sites is largely dependent upon their fate and behaviour. The weathering of particles in the environment and the potential release of the radioactivity they contain is influenced by a range of factors including particle morphology, elemental composition and chemical form, and the prevailing environmental conditions. Radioactive particles have been isolated from soils and sediments from Australian test sites and characterised using photostimulated luminescence (PSL)-autoradiography, scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS), Synchrotron X-ray fluorescence microscopy (XFM) and particle-induced X-ray emission (PIXE). The characteristics of the particles and potential implications for their long term fate will be discussed in the context of the techniques applied and the environments in which the particles were found.
Cultural heritage project at Australian Nuclear Science and Technology Organisation (ANSTO)
(Springer Nature, 2022-01-25) Salvemini, F; White, R; Levchenko, VA; Smith, AM; Pastuovic, Z; Stopic, A; Luzin, V; Tobin, MJ; Puskar, L; Howard, DL; Davis, J; Avdeev, M; Gatenby, S; Kim, MJ; Grazzi, F; Sheedy, K; Olsen, SR; Raymond, CA; Lord, C; Richards, C; Bevitt, JJ; Popelka-Filcoff, RS; Lenehan, CE; Ives, S; Dredge, P; Yip, A; Brookhouse, MT; Austin, AG
The Australian Nuclear Science and Technology Organization (ANSTO) is the home of Australia’s most significant landmark and national infrastructure for research. ANSTO operates one of the world’s most modern nuclear research reactors, OPAL; a comprehensive suite of neutron beam instruments; the Australian Synchrotron; the Electron Microscope Facility; and the Center for Accelerator Science. Over the years, the suite of nuclear methods available across ANSTO’s campuses has been increasingly applied to study a wide range of heritage materials. Since 2015 the strategic research project on cultural heritage was initiated in order to promote access to ANSTO’s capabilities and expertise, unique in the region, by cultural institution and researchers. This chapter offers a compendium of ANSTO nuclear capabilities most frequently applied to cultural heritage research. A series of innovative, interdisciplinary, and multi-technique studies conducted in close collaboration with Australian museums, institutions, and universities is also showcased. It includes research on dating Aboriginal Australian rock art and fingerprinting the sources of ochre pigments; rediscovering the technological knowledge in the making of early coinage and ancient weapons; virtually unwrapping the content of votive mummies from ancient Egypt; and investigating and restoring the original layer of a painting that can be explored by the museum audience in a novel type of exhibition based on an immersive, interactive, and virtual environment. © 2022 Springer Nature Switzerland AG
Direct imaging of endogenous biometal distributions within millimetre-scale organisms at micrometre resolution – x-ray fluorescence tomography
(Australian Microscopy and Microanalysis Society, 2016-02-04) de Jonge, MD; Ruben, G; Mayo, SS; Ryan, CG; Kirkham, R; Howard, DL; Paterson, DJ
First-row transition metals are required for all forms of life on earth. The high reactivity of these elements means that an array of mechanisms has evolved to regulate key processes governing their transport and binding action. Tracking metals within biological tissue is non-trivial; tagging approaches suffer from lack of specificity, and can fail to find strongly-bound species; in addition, tags can interfere with normal biochemistry. Electron microscopy provides stupendous resolution, but probes miniscule volumes due to the short penetration of electrons. With μM sensitivity, X-ray Fluorescence Microscopy (XFM) can probe endogenous metal concentrations at resolutions at the μm length scale. Elemental maps are quantitative. With penetration depth and depth of field well matched at around 0.5 mm, the method can be up-scaled to 3-D visualisations via tomography. Here we report on our application of X-ray fluorescence tomography of Zn, Cu, Fe, and Mn in C. elegans and discuss recent progress in developing self-absorption corrections that will enable accurate mapping of light elements.
Fast high-resolution synchrotron micro-XRF mapping of annually laminated stalagmites
(Copernicus GmbH, 2019-04-11) Borsato, A; Frisia, S; Hellstrom, JC; Treble, PC; Johnson, K; Howard, DL; Greig, A
Annual lamination in trace elements content allows to improve speleothem chronology as well as to extract paleoclimate information about fluctuations of the seasonal signal through time. Given the relatively slow growth and textural heterogeneity intrinsic in most speleothems, only high-resolution mapping techniques provide a viable approach to resolve trace elements variability at annual to sub-annual scale. Synchrotron radiation X-ray fluorescence microscopy (SR-μXRF) is, to date, the ideal technique as it provides quantitative, non-destructive fast scanning of large samples at the necessary high spatial resolution (0.5 – 5 μm). Here we present SR-μXRF investigation of U/Th dated stalagmites from caves in different geographic and climate setting including semi-arid (Flinders Ranges, South Australia), temperate (Central Italy) and tropical humid (Cook Islands, Northern Laos) climates. SR-μXRF analyses were coupled with high-resolution petrographic observation and LA-ICP-MS elemental analyses in order to verify the XRF elemental quantification and to test the relationship between fabric and trace element incorporation. All the analysed stalagmites revealed faint to sharp annual lamination in Sr, and, occasionally, in other elements such as Br, Cu and Zn. In climate setting characterised by strong seasonal contrast stalagmites often exhibit fabric changes at annual to centennial scale that are reflected in the internal porosity as well as in the incorporation of trace elements. Fabric control and spatial heterogeneity is also evident in the intensity of the annual cycles and, in some cases, the amplitude of Sr cycles vary considerably from one line scan to the adjacent ones. This poses the question of the significance and reproducibility of trace element analyses in speleothems characterised by fabric heterogeneity. © Author(s) 2019. CC Attribution 4.0 license.
Geomaterials in the age of megapixel imaging
(Australian Microscopy and Microanalysis Society, 2016-02-04) Brugger, J; Etschmann, BE; Li, K; Michaut, P; Donner, E; Howard, DL
Geological samples are extremely diverse and share a tendency for heterogeneity and complexity. This is especially true for ores and for environmental samples, which result from complex processes in dynamic environments. In recent years, a number of tools that enable imaging element distribution in geological samples at 1-50μm-resolution and over cm2 areas have seen rapid development and have become readily available. The application of synchrotron-based X-ray fluorescence mapping has been limited to addressing key questions because of low availability and high cost. However, recent advances in X-ray fluorescence detector technology are bringing new possibilities to petrology. Millisecond dwell times allow collection of thin-section-size maps in hours, and improvement in data analysis produces quantitative elemental maps. The technique can be combined with XANES imaging to provide additional information about element speciation (e.g., As oxidation state). We illustrate applications of M(egapixel)-μXRF for ore petrology (commodities: Au, Pt, U, Cu, Ge, Ti, REE, Nb), coal petrology, and environmental samples. Examples of outcomes include: (i) the distribution of μm-sized Pt-rich grains and Ti-mobility during schistosity formation at the Fifield Pt prospect (Australia); (ii) confirmation of the two-stage Ge-enrichment in the Barrigão deposit (Portugal), with demonstration of the presence of Ge in solid solution in the early chalcopyrite; (iii) enrichment of U during late dissolution-reprecipitation reactions in the Cu-rich ores of the Moonta and Wallaroo IOCG deposits (Australia); (iv) history of REE-Ti-Nb-(As) mobility during amphibolite to greenschist facies metamorphism in the Binntal Valley, Switzerland; (v) contrasting distribution of As, Ge and W in Ge-rich coals across the Globe; and (vi) evolution of the distribution and speciation of Cu upon aging of biosolids.
Havre 2012 pink pumice is evidence of a short-lived, deep-sea, magnetite nanolite-driven explosive eruption
(Goldschmidt, 2022-07-16) Knafelc, J; Byran, SE; Jones, MWM; Gust, D; Mallmann, G; Cathey, H; Berry, A; Ferré, EC; Howard, DL
The Havre 2012 deep-sea eruption produced a massive pumice raft (~1.2 km3) at the sea surface from a volcano that sits 900 mbsl (~9.6 MPa) in the Kermadec Arc. Lava flows/domes and a field of sunken seafloor pumice were also emplaced across the summit during the eruption. Havre raft and seafloor pumice are considered to have erupted contemporaneously and as part of an effusive eruption due their similarity in appearance and bulk chemistry. A distinctive feature of the raft is the common occurrence of pink pumice. Pink pumice has been reported from subaerial explosive eruptions, and results from high-temperature atmospheric iron-oxidation (> 700 °C). The pink raft pumice therefore poses problems given the deep water setting that is assumed to prevent eruption explosivity and the effusive eruption model for the 2012 eruption. Here, pink pumice is experimentally produced by heating white Havre raft pumice for several minutes in air at temperatures between 675-900°C (Fig. 1). The degree of reddening in experimental pumices increases with increased temperatures and times, resulting in a similar spectrum of colouration observed in natural pink raft pumice. The origin of the pink colouration was then investigated using several microanalytical techniques including X-ray Fluorescence Microscopy (XFM), Fe X-ray Absorption Near Edge structures (Fe-XANES), EPMA, rock magnetics, and TEM imaging. We found that white and pink raft pumice contain abundant magnetite nanolites/microlites and higher amounts of hematite in the pink pumice. In contrast, no magnetite nanolites or hematite occurs in the seafloor pumice. Magnetite nanolites line vesicle walls of pink raft pumice where the colour is microscopically localized. This provides evidence the magnetite nanolites are oxidizing to hematite and also acted as nucleation sites for enhanced volatile exsolution. Our results demonstrate a short-lived but powerful explosive eruption phase occurred during the 2012 eruption that penetrated the water column allowing hot pyroclasts to oxidize in air (Fig. 2). In light of these results the known depth limits for explosive eruptions (~10 MPa) in the marine realm need to be reassessed and we suggest pink pumice can be an indicator of magnetite nanolite-driven explosive eruptions.
Palaeolithic cave art in Borneo
(Springer Nature, 2018-11-11) Aubert, M; Setiawan, P; Oktaviana, AA; Brumm, A; Sulistyarto, PH; Saptomo, EW; Istiawan, B; Ma'rifat, TA; Wahyuono, VN; Atmoko, FT; Zhao, JX; Huntley, J; Taçon, PSC; Howard, DL; Brand, HEA
Figurative cave paintings from the Indonesian island of Sulawesi date to at least 35,000 years ago (ka) and hand-stencil art from the same region has a minimum date of 40 ka1. Here we show that similar rock art was created during essentially the same time period on the adjacent island of Borneo. Uranium-series analysis of calcium carbonate deposits that overlie a large reddish-orange figurative painting of an animal at Lubang Jeriji Saléh—a limestone cave in East Kalimantan, Indonesian Borneo—yielded a minimum date of 40 ka, which to our knowledge is currently the oldest date for figurative artwork from anywhere in the world. In addition, two reddish-orange-coloured hand stencils from the same site each yielded a minimum uranium-series date of 37.2 ka, and a third hand stencil of the same hue has a maximum date of 51.8 ka. We also obtained uranium-series determinations for cave art motifs from Lubang Jeriji Saléh and three other East Kalimantan karst caves, which enable us to constrain the chronology of a distinct younger phase of Pleistocene rock art production in this region. Dark-purple hand stencils, some of which are decorated with intricate motifs, date to about 21–20 ka and a rare Pleistocene depiction of a human figure—also coloured dark purple—has a minimum date of 13.6 ka. Our findings show that cave painting appeared in eastern Borneo between 52 and 40 ka and that a new style of parietal art arose during the Last Glacial Maximum. It is now evident that a major Palaeolithic cave art province existed in the eastern extremity of continental Eurasia and in adjacent Wallacea from at least 40 ka until the Last Glacial Maximum, which has implications for understanding how early rock art traditions emerged, developed and spread in Pleistocene Southeast Asia and further afield. © 2018 Springer Nature Limited
Polycrystalline materials analysis using the Maia pixelated energy-dispersive x-ray area detector
(Cambridge University Press, 2017-09-26) Kirkwood, HJ; De Jonge, MD; Howard, DL; Ryan, CG; van Riessen, GA; Hofmann, F; Rowles, MR; Paradowska, AM; Abbey, B
Elemental, chemical, and structural analysis of polycrystalline materials at the micron scale is frequently carried out using microfocused synchrotron X-ray beams, sometimes on multiple instruments. The Maia pixelated energy-dispersive X-ray area detector enables the simultaneous collection of X-ray fluorescence (XRF) and diffraction because of the relatively large solid angle and number of pixels when compared with other systems. The large solid angle also permits extraction of surface topography because of changes in self-absorption. This work demonstrates the capability of the Maia detector for simultaneous measurement of XRF and diffraction for mapping the short- and long-range order across the grain structure in a Ni polycrystalline foil. Copyright © International Centre for Diffraction Data 2017
Quantifiying the fire imprint in speleothem oxygen and carbon isotope records
(American Geophysical Union (AGU), 2022-12-14) Baker, AA; Campbell, M; Treble, PC; Adler, L; McDonough, LK; Howard, DL
Speleothems are an emerging archive of past fires. Fires primarily leave an imprint in speleothem calcite from ash-derived water-soluble trace elements transported from the surface to the cave in percolation waters. But what about the influence of fire on speleothem oxygen and carbon isotopes? Oxygen and carbon isotopes are the most widely used speleothem geochemical proxies, generally interpreted as archives of past climatic and environmental change. The link between speleothem oxygen and carbon isotopes and fire, however, is still unclear. Field monitoring before and after recent fires provides some clues to the possible fire effect on speleothem oxygen isotope composition. Recent papers present evidence that cave percolation water can have oxygen isotope composition that is enriched in oxygen-18 post-fire, due to partial evaporation of soil water and loss of shade cover. There is also evidence indicating that post-fire, percolation waters have greater variability in oxygen-18 when there is complete evaporation of soil water. To better understand the influence of fire on speleothem oxygen and carbon isotopes, we have sampled ~10 mm from the tops of actively-depositing stalagmites from cave systems at Yanchep, Western Australia. The sampled material contains calcite that has formed over the last ~50 years, during which numerous fires have occurred at the site. The data spans the period of satellite monitoring, allowing fire size and intensity to be determined. We use synchrotron x-ray fluorescence imaging to map the trace element composition of the stalagmites, and use this to identify the fire imprint of the ash-derived water-soluble elements in the stalagmite calcite. Using this as a time marker of the fires, we quantify the magnitude and duration of any post-fire changes in stalagmite oxygen and carbon stable isotope composition. We identify whether changes in oxygen or carbon isotopes are replicated between stalagmites and between fire events, and compare the extent to which the post-fire imprint in stalagmite oxygen and carbon isotopes is significant compared to climatic and hydrological controls on these isotopes. This information will inform paleoclimate studies where shifts in speleothem oxygen and carbon isotopes due to fires may be misinterpreted to result from changes in climate and hydrology. Full Abstract Are wildfires increasing in number, intensity or spatial extent compared to the past? Before the era of satellite imaging, we have to rely on geological and biological archives of past fires. One such archive is cave stalagmites. However, they are normally used as an archive of past climate through the analysis of oxygen isotopes contained within their calcite. And wildfire can affect the oxygen isotope composition of the water percolating from the surface to the cave through the burnt environment. To what extent does wildfire affect the stalagmite climate archive? Here, we compare stalagmite records from caves in a region in Western Australia that has burnt many times in recent decades. We identify the fire imprint in the stalagmite calcite using synchrotron mapping of ash-derived elements. And we line these fire events up with the stable isotope record in the same sample. That way we can quantify the fire imprint in the stalagmite oxygen isotope record for the first time. This will allow future researchers to take this into consideration when interpretating stalagmite oxygen isotope records from fire-prone regions.
Research in art and archaeology: capabilities and investigations at the Australian Synchrotron
(Taylor & Francis, 2019-11-26) Brand, HEA; Howard, DL; Huntley, J; Kappen, P; Masimenko, A; Paterson, DJ; Puskar, L; Tobin, MJ
In the Australian Synchrotron's short history, we have made some important advances in instruments and capabilities that can be employed to study art and archaeology. In this article, we describe the capabilities at the Australian Synchrotron that are well-suited to investigating art, archaeology, and cultural heritage. We also present some case studies that demonstrate the breadth and impact of science that has been performed by researchers using these capabilities. Synchrotron radiation has many advantages that make it ideally suited to investigating art, archaeology and cultural heritage. The broad spectrum of radiation that can be employed and, in particular, the penetrating nature of the radiation at hard X-ray energies give the ability to conduct 3D reconstruction with tomography. In many cases, the techniques can be non-destructive and performed in situ. The intense infrared radiation allows infrared microscopy at diffraction-limited resolution and the recently developed attenuated total internal reflection mode can probe the surface of very delicate samples. In the following, we describe the relevant beamlines, their capabilities, and then illustrate with some key examples of research, from paleobotany to the investigation of paintings. © 2019 Informa UK Limited
Simultaneous X-ray diffraction, crystallography and fluorescence mapping using the Maia detector
(Elsevier, 2018-02-01) Kirkwood, HJ; de Jonge, MD; Muránsky, O; Hofmann, F; Howard, DL; Ryan, CG; van Riessen, GA; Rowles, MR; Paradowska, AM; Abbey, B
Interactions between neighboring grains influence the macroscale behavior of polycrystalline materials, particularly their deformation behavior, damage initiation and propagation mechanisms. However, mapping all of the critical material properties normally requires that several independent measurements are performed. Here we report the first grain mapping of a polycrystalline foil using a pixelated energy-dispersive X-ray area detector, simultaneously measuring X-ray fluorescence and diffraction with the Maia detector in order to determine grain orientation and estimate lattice strain. These results demonstrate the potential of the next generation of X-ray area detectors for materials characterization. By scanning the incident X-ray energy we investigate these detectors as a complete solution for simultaneously mapping the crystallographic and chemical properties of the sample. The extension of these techniques to broadband X-ray sources is also discussed. © 2017 Acta Materialia Inc. Published by Elsevier Ltd.
Strontium mineralization of shark vertebrae
(Nature Publishing Group, 2016-07-18) Raoult, VV; Peddemors, VM; Zahra, D; Howell, NR; Howard, DL; de Jonge, MD; Williamson, JE
Determining the age of sharks using vertebral banding is a vital component of management, but the causes of banding are not fully understood. Traditional shark ageing is based on fish otolith ageing methods where growth bands are assumed to result from varied seasonal calcification rates. Here we investigate these assumptions by mapping elemental distribution within the growth bands of vertebrae from six species of sharks representing four different taxonomic orders using scanning x-ray fluorescence microscopy. Traditional visual growth bands, determined with light microscopy, were more closely correlated to strontium than calcium in all species tested. Elemental distributions suggest that vertebral strontium bands may be related to environmental variations in salinity. These results highlight the requirement for a better understanding of shark movements, and their influence on vertebral development, if confidence in age estimates is to be improved. Analysis of shark vertebrae using similar strontium-focused elemental techniques, once validated for a given species, may allow more successful estimations of age on individuals with few or no visible vertebral bands. © 2016 Macmillan Publishers Limited
Studying biological coordination chemistry: a useful role for low latency, energy-dispersive photon counting XRF detectors
(Australian Microscopy and Microanalysis Society, 2016-02-04) James, S; de Jonge, MD; McColl, G; Burke, R; Paterson, DJ; Howard, DL; Hare, D
Day to day cellular function is fundamentally dependent on electron transfer reactions mediated by transition metals, often iron and/or copper. The biological consequences of this metal-catalysed redox chemistry arise from biochemical context generated via the multi-scale organisation of biological systems, i.e. the local concentration of metal → the nature of the donor atoms and bonding environment within the ligand → the location and abundance of the ligand within the cell → the suite of metal-ligand complexes comprising a cell’s metallome → the differences between one cell’s instance of it’s metallome compared to another within and between tissues. Biochemical insight must be anchored to the structural biology of the cell. In this view, understanding metallobiology requires us to interrogate the coordination environment of biological metal-ligand complexes in situ, and the lack of suitable probes limits our appreciation for the role metallobiology plays in health and disease. Ideally, such probes must exhibit extremely high specificity, sensitivity, and spatial resolution; requirements met by scanning X-ray fluorescence microscopy (XFM) and X-ray Emission Near Edge Structure (XENES). Advances in energy-dispersive detector technology have enormously enhanced the efficiency and speed of data acquisition when performing XFM and XENES measurements. When using the Maia detector system installed at the Australian Synchrotron XFM beamline the distribution of biometals can be mapped at rates in excess of 3 M pix / hr. This speed reduces imaging dose whilst maintaining counting statistics. Exploiting these technical advances we have undertaken a multi-pronged assault on characterising elemental distribution and speciation in a variety of whole- organism biological systems, including Caenorhabditis elegans and Drosophila melanogaster. We have utilised projective elemental mapping and 3D visualisations of elemental distributions to assess the distribution of chemical speciation through XENES imaging and tomography. The complementarity of these studies demonstrates that volumetric chemical speciation is achievable with the right instrumentation and approach to measurement but projective imaging can still provide a window into fundamental biological processes. Opportunities and challenges associated with visualizing in situ biometal speciation will be discussed.
Tandem probe analysis mode for synchrotron XFM: doubling throughput capacity
(American Chemical Society (ACS), 2022-03-22) Doolette, CL; Howard, DL; Afshar, N; Kewish, CM; Paterson, DJ; Huang, J; Wagner, S; Santner, J; Wenzel, WW; Raimondo, T; De Vries Van Leeuwen, AT; Hou, L; van der Bom, F; Weng, H; Kopittke, PM; Lombi, E
Synchrotron-based X-ray fluorescence microscopy (XFM) analysis is a powerful technique that can be used to visualize elemental distributions across a broad range of sample types. Compared to conventional mapping techniques such as laser ablation inductively coupled plasma mass spectrometry or benchtop XFM, synchrotron-based XFM provides faster and more sensitive analyses. However, access to synchrotron XFM beamlines is highly competitive, and as a result, these beamlines are often oversubscribed. Therefore, XFM experiments that require many large samples to be scanned can penalize beamline throughput. Our study was largely driven by the need to scan large gels (170 cm2) using XFM without decreasing beamline throughput. We describe a novel approach for acquiring two sets of XFM data using two fluorescence detectors in tandem; essentially performing two separate experiments simultaneously. We measured the effects of tandem scanning on beam quality by analyzing a range of contrasting samples downstream while simultaneously scanning different gel materials upstream. The upstream gels were thin (<200 μm) diffusive gradients in thin-film (DGT) binding gels. DGTs are passive samplers that are deployed in water, soil, and sediment to measure the concentration and distribution of potentially bioavailable nutrients and contaminants. When deployed on soil, DGTs are typically small (2.5 cm2), so we developed large DGTs (170 cm2), which can be used to provide extensive maps to visualize the diffusion of fertilizers in soil. Of the DGT gel materials tested (bis-acrylamide, polyacrylamide, and polyurethane), polyurethane gels were most suitable for XFM analysis, having favorable handling, drying, and analytical properties. This gel type enabled quantitative (>99%) transmittance with minimal (<3%) flux variation during raster scanning, whereas the other gels had a substantial effect on the beam focus. For the first time, we have (1) used XFM for mapping analytes in large DGTs and (2) developed a tandem probe analysis mode for synchrotron-based XFM, effectively doubling throughput. The novel tandem probe analysis mode described here is of broad applicability across many XFM beamlines as it could be used for future experiments where any uniform, highly transmissive sample could be analyzed upstream in the "background"of downstream samples. © 2022 The Authors. Published by American Chemical Society.
A technique for preparing undecalcified osteochondral fresh frozen sections for elemental mapping and understanding disease etiology
(Springer Nature, 2022-07-09) Fan, XW; Lee, KM; Jones, MWM; Howard, DL; Crawford, R; Prasadam, I
The anatomy of the osteochondral junction is complex because several tissue components exist as a unit, including uncalcified cartilage (with superficial, middle, and deep layers), calcified cartilage, and subchondral bone. Furthermore, it is difficult to study because this region is made up of a variety of cell types and extracellular matrix compositions. Using X-ray fluorescence microscopy, we present a protocol for simultaneous elemental detection on fresh frozen samples. We transferred the osteochondral sample using a tape-assisted system and successfully tested it in synchrotron X-ray fluorescence. This protocol elucidates the distinct distribution of elements at the human knee’s osteochondral junction, making it a useful tool for analyzing the co-distribution of various elements in both healthy and diseased states. © The Author(s) 2022 - Open Access under a Creative Commons Attribution 4.0 International License,
Towards the development of fire proxies in speleothems using geochemical signatures in ashes from bushfires
(Australasian Quaternary Association Inc., 2022-12-06) Campbell, M; McDonough, LK; Naeher, S; Treble, PC; Grierson, P; Sinclair, D; Howard, DL; Baker, AA
Our knowledge of past fire regimes is limited by short observational records. Proxy archives (such as sediment cores, ice cores, speleothems, and tree scars) are used to extend these records and develop a better understanding of past fire regimes. Recently, stalagmites (i.e., cave deposits), have been shown to record past fire events, and it is possible that they include other attributes of the fire regime (e.g. burn severity). Stalagmite fire proxies are both chemical (e.g. oxygen isotope composition of calcite, and nutrient and trace metal concentrations), and physical (e.g. growth rate, fabric). Trace metals and nutrients are leached from ash and subsequently transported to the stalagmite via hydrological pathways. We collected ash from four Australian karst sites which experienced fires in recent years (2019 and 2022). Ash chemical composition was determined by analysis of leachates (inorganic chemistry) and by analysis of the ash itself (organic biomarker concentrations of a subset of the ash dataset). The concentrations of inorganic components (e.g. of trace metals strontium and magnesium) show a clear difference between more- and less-combusted materials, as inferred by ash colour. Common fire biomarker concentrations (e.g. polycyclic aromatic hydrocarbons and levoglucosan) showed no clear relationship with inferred burn severity. Together, this has implications for the use of both organic and inorganic fire proxies in stalagmites and other sedimentary proxy archives. Inorganic ash geochemistry results will be used to contextualise changes in stalagmite geochemistry from Western Australian stalagmites (as measured by LA-ICP-MS and Synchrotron micro-XFM) which experienced bushfires during the satellite era. We aim to determine whether stalagmite chemistry can be used as a proxy for burn severity.
Towards the development of fire proxies in speleothems using geochemical signatures in ashes from bushfires
(Australasian Quaternary Association Inc., 2022-12-06) Campbell, M; McDonough, LK; Naeher, S; Treble, PC; Grierson, P; Sinclair, D; Howard, DL; Baker, AA
Our knowledge of past fire regimes is limited by short observational records. Proxy archives (such as sediment cores, ice cores, speleothems, and tree scars) are used to extend these records and develop a better understanding of past fire regimes. Recently, stalagmites (i.e., cave deposits), have been shown to record past fire events, and it is possible that they include other attributes of the fire regime (e.g. burn severity). Stalagmite fire proxies are both chemical (e.g. oxygen isotope composition of calcite, and nutrient and trace metal concentrations), and physical (e.g. growth rate, fabric). Trace metals and nutrients are leached from ash and subsequently transported to the stalagmite via hydrological pathways. We collected ash from four Australian karst sites which experienced fires in recent years (2019 and 2022). Ash chemical composition was determined by analysis of leachates (inorganic chemistry) and by analysis of the ash itself (organic biomarker concentrations of a subset of the ash dataset). The concentrations of inorganic components (e.g. of trace metals strontium and magnesium) show a clear difference between more- and less-combusted materials, as inferred by ash colour. Common fire biomarker concentrations (e.g. polycyclic aromatic hydrocarbons and levoglucosan) showed no clear relationship with inferred burn severity. Together, this has implications for the use of both organic and inorganic fire proxies in stalagmites and other sedimentary proxy archives. Inorganic ash geochemistry results will be used to contextualise changes in stalagmite geochemistry from Western Australian stalagmites (as measured by LA-ICP-MS and Synchrotron micro-XFM) which experienced bushfires during the satellite era. We aim to determine whether stalagmite chemistry can be used as a proxy for burn severity.

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