Showing items 1 - 4 of 4

Iron(III) accumulations in inland saline waterways, Hunter Valley, Australia : Mineralogy, micromorphology and pore-water geochemistry

- Isaacson, Lloyd, Burton, Edward, Bush, Richard, Mitchell, David, Johnston, Scott, Macdonald, Bennett, Sullivan, Leigh, White, Ian

  • Authors: Isaacson, Lloyd , Burton, Edward , Bush, Richard , Mitchell, David , Johnston, Scott , Macdonald, Bennett , Sullivan, Leigh , White, Ian
  • Date: 2009
  • Type: Text , Journal article
  • Relation: Applied Geochemistry Vol. 24, no. 10 (2009), p. 1825-1834
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  • Description: Discharge of Fe(II)-rich groundwaters into surface-waters results in the accumulation of Fe(III)-minerals in salinized sand-bed waterways of the Hunter Valley, Australia. The objective of this study was to characterise the mineralogy, micromorphology and pore-water geochemistry of these Fe(III) accumulations. Pore-waters had a circumneutral pH (6.2-7.2), were sub-oxic to oxic (Eh 59-453 mV), and had dissolved Fe(II) concentrations up to 81.6 mg L-1. X-ray diffraction (XRD) on natural and acid-ammonium-oxalate (AAO) extracted samples indicated a dominance of 2-line ferrihydrite in most samples, with lesser amounts of goethite, lepidocrocite, quartz, and alumino-silicate clays. The majority of Fe in the samples was bound in the AAO extractable fraction (FeOx) relative to the Na-dithionite extractable fraction (FeDi), with generally high FeOx:FeDi ratios (0.52-0.92). The presence of nano-crystalline 2-line ferrihydrite (Fe5HO3·4H2O) with lesser amounts of goethite (α-FeOOH) was confirmed by scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX), and transmission electron microscopy (TEM) coupled with selected area electron diffraction (SAED). In addition, it was found that lepidocrocite (γ-FeOOH), which occurred as nanoparticles as little as ∼5 lattice spacings thick perpendicular to the (0 2 0) lattice plane, was also present in the studied Fe(III) deposits. Overall, the results highlight the complex variability in the crystallinity and particle-size of Fe(III)-minerals which form via oxidation of Fe(II)-rich groundwaters in sand-bed streams. This variability may be attributed to: (1) divergent precipitation conditions influencing the Fe(II) oxidation rate and the associated supply and hydrolysis of the Fe(III) ion, (2) the effect of interfering compounds, and (3) the influence of bacteria, especially Leptothrix ochracea. © 2009 Elsevier Ltd. All rights reserved.

Iron-monosulfide oxidation in natural sediments : Resolving microbially mediated S transformations using XANES, electron microscopy, and selective extractions

- Burton, Edward, Bush, Richard, Sullivan, Leigh, Hocking, Rosalie, Mitchell, David, Johnston, Scott, Fitzpatrick, Rob W., Raven, Mark, McClure, Stuart, Jang, Lingyun

  • Authors: Burton, Edward , Bush, Richard , Sullivan, Leigh , Hocking, Rosalie , Mitchell, David , Johnston, Scott , Fitzpatrick, Rob W. , Raven, Mark , McClure, Stuart , Jang, Lingyun
  • Date: 2009
  • Type: Text , Journal article
  • Relation: Environmental Science and Technology Vol. 43, no. 9 (2009), p. 3128-3134
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  • Description: Iron-monosulfide oxidation and associated S transformations in a natural sediment were examined by combining selective extractions, electron microscopy and S K-edge X-ray absorption near-edge structure (XANES) spectroscopy. The sediment examined in this study was collected from a waterway receiving acid-sulfate soil drainage. It contained a high acid-volatile sulfide content (1031 μ mol g-1), reflecting an abundance of iron-monosulfide. The iron-monosulfide speciation in the initial sediment sample was dominated by nanocrystalline mackinawite (tetragonal FeS). At near-neutral pH and an O 2 partial pressure of ∼0.2 atm, the mackinawite was found to oxidize rapidly, with a half-time of 29 ± 2 min. This oxidation rate did not differ significantly (P < 0.05) between abiotic versus biotic conditions, demonstrating that oxidation of nanocrystalline mackinawite was not microbially mediated. The extraction results suggested that elemental S (S0 8) was a key intermediate S oxidation product. Transmission electron microscopy showed the S0 8 to be amorphous nanoglobules, 100-200 nm in diameter. The quantitative importance of S0 8 was confirmed by linear combination XANES spectroscopy, after accounting for the inherent effect of the nanoscale S0 8 particle-size on the corresponding XANES spectrum. Both the selective extraction and XANES data showed that oxidation of S0 8 SO4 2- was madiated by microbial activity. In addition to directly revealing important S transformations, the XANES results support the accuracy of the selective extraction scheme employed here. © 2009 American Chemical Society.

Schwertmannite transformation to goethite via the Fe(II) pathway : Reaction rates and implications for iron-sulfide formation

- Burton, Edward, Bush, Richard, Sullivan, Leigh, Mitchell, David

  • Authors: Burton, Edward , Bush, Richard , Sullivan, Leigh , Mitchell, David
  • Date: 2008
  • Type: Text , Journal article
  • Relation: Geochimica et Cosmochimica Acta Vol. 72, no. 18 (2008), p. 4551-4564
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  • Description: Schwertmannite (Fe8O8(OH)6SO4) is a common Fe(III)-oxyhydroxysulfate mineral in acid-sulfate systems, where its formation and fate strongly influence water quality. The present study examines transformation of schwertmannite to goethite (FeOOH), as catalyzed by interactions with Fe(II) in anoxic aquatic environments. This study also evaluates the role of the Fe(II) pathway in influencing the formation of iron-sulfide minerals in such environments. At pH > 5, the rates of Fe(II)-catalyzed schwertmannite transformation were several orders of magnitude faster than transformation in the absence of Fe(II). Complete transformation of schwertmannite occurred within only 3-5 h at pH > 6 and Fe(II)(aq) ≥ 5 mmol L-1. Model calculations indicate that the Fe(II)-catalyzed transformation of schwertmannite to goethite greatly decreases the reactivity of the Fe(III) pool, thereby favoring SO4-reduction and facilitating the formation of iron-sulfide minerals (particularly mackinawite, tetragonal FeS). Examination of in situ sediment geochemistry in an acid-sulfate system revealed that the rapid Fe(II)-catalyzed transformation was consistent with an abrupt shift from an acidic Fe(III)-reducing regime with abundant schwertmannite near the sediment surface, to a near-neutral mackinawite-forming regime where goethite was dominant. This study demonstrates that the Fe(II) pathway exerts a major influence on schwertmannite transformation and iron-sulfide formation in anoxic acid-sulfate systems. These findings have important implications for understanding acidity dynamics and trace element mobility in such systems. © 2008 Elsevier Ltd. All rights reserved.

The use of intra-articular platelet rich plasma for the symptomatic management of osteoarthritis of the knee : a pilot study

- Sibillin, Olivia, Mitchell, David, Harris, Greg, Harvey, Jack, Spencer, Polly, Spencer, Luke

  • Authors: Sibillin, Olivia , Mitchell, David , Harris, Greg , Harvey, Jack , Spencer, Polly , Spencer, Luke
  • Date: 2022
  • Type: Text , Journal article
  • Relation: ANZ Journal of Surgery Vol. 92, no. 5 (2022), p. 1178-1183
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  • Description: Background: Osteoarthritis of the knee is a chronic inflammatory condition resulting in significant patient disability, with intra-articular platelet rich plasma (PRP) injections having shown potential to improve symptomatic outcomes. This retrospective cohort pilot study aimed to observe whether PRP injections were beneficial in the symptomatic management of knee osteoarthritis in an Australian population, based on patient reported outcomes. An additional aim was to observe for an association between the number of injections and patient characteristics, such as body mass index, age, sex and radiologically determined severity of the disease. Methods: The cohort was drawn from those who attended Ballarat Orthopaedic and Sports Medicine for PRP injections and who had completed the appropriate pre- and post-injection Western Ontario and McMaster Universities Arthritis Index (WOMAC) questionnaire. WOMAC scores were analysed to observe for any difference following a course of PRP injections. Results: The data suggest that the use of PRP improved patient reported WOMAC scores. Additionally, it was shown that two injections had a greater effect than one injection, with a third injection providing no further benefit. Finally, there was an association with lower WOMAC scores post PRP therapy amongst male participants compared to female participants. Conclusion: These results suggest two PRP injections are optimal for the symptomatic management of knee osteoarthritis, identifying a need for further prospective research in this Australian population. © 2022 Royal Australasian College of Surgeons.
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