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Arsenic microdistribution and speciation in toenail clippings of children living in a historic gold mining area

- Pearce, Dora, Dowling, Kim, Gerson, Andrea, Sim, Malcolm, Sutton, Stephen, Newville, Matthew, Russell, Robert, McOrist, Gordon

  • Authors: Pearce, Dora , Dowling, Kim , Gerson, Andrea , Sim, Malcolm , Sutton, Stephen , Newville, Matthew , Russell, Robert , McOrist, Gordon
  • Date: 2010
  • Type: Text , Journal article
  • Relation: Science of the Total Environment Vol. 408, no. 12 (2010), p. 2590-2599
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  • Description: Arsenic is naturally associated with gold mineralisation and elevated in some soils and mine waste around historical gold mining activity in Victoria, Australia. To explore uptake, arsenic concentrations in children's toenail clippings and household soils were measured, and the microdistribution and speciation of arsenic in situ in toenail clipping thin sections investigated using synchrotron-based X-ray microprobe techniques. The ability to differentiate exogenous arsenic was explored by investigating surface contamination on cleaned clippings using depth profiling, and direct diffusion of arsenic into incubated clippings. Total arsenic concentrations ranged from 0.15 to 2.1

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.
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