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Southern Cross GeoScience

Iron-monosulfide formation and oxidation in acid-sulfate soils

Funding:

  • Australian Research Council (DP0772050 'Unravelling the oxidative geochemistry of nanoparticulate mackinawite in acid-sulfate soil landscapes' Chief Investigators: Burton, Bush, Sullivan)
  • Australian Institute of Nuclear Science & Engineering
  • National Synchrotron Radiation Research Centre (Taiwan)
  • Australian Synchrotron Research Program

Project description:

Poor water quality in acid sulfate soil (ASS) landscapes is a widely recognised international problem. Research and management over the past three decades have focused largely on pyrite oxidation and the release of acid-sulfate leachate into floodplain waterways. However, in addition to iron-disulfides (such as pyrite), ASS landscapes often contain large amounts of iron-monosulfide minerals. The formation and oxidation of iron-monosulfides has a fundamental role in regulating water quality through effects on acidity dynamics and the mobility of iron, sulfur and trace metals (Burton et al., 2006b). The objective of this project is to better understand the formation and oxidation of iron-monosulfides in ASS landscapes.

Iron-monosulfide Figure 1
Figure 1. Mackinawite (FeS) in acid-sulfate soil material. (a) electron diffraction pattern, with transmission electron microscope images of individual FeS nanocrystals.
Iron-monosulfide Figure 2
Figure 2. Changes in (a) XRD and (b) S XANES spectra during oxidation of an FeS-rich acid-sulfate soil material. The labels in (a) are Q = quartz, G = goethite, Sd = siderite, P = pyrite and FeSM denotes the diffraction spacing due to preferred orientation of the (001) plane in nanoparticulate mackinawite. The labels in (b) correspond to the energy of maximum XANES absorption intensity for mackinawite, elemental S and sulfate standards. The circles in (b) represent XANES data points, whilst the solid-line shows the quantitative linear combination fit to the data.

SCGS Team members:

  • Edward Burton
  • Richard Bush
  • Leigh Sullivan

Contact:

For further information contact Dr Ed Burton
ed.burton@scu.edu.au

Relevant publications:

Burton, E.D., Bush, R.T., Sullivan, L.A., Hocking, R.K., Mitchell, D.R.G., Johnston, S.G., Fitzpatrick, R.W., Raven, M., McClure, S., Jang, L.Y. (2009) Iron-monosulfide oxidation in natural sediments: Resolving microbially-mediated S transformations using XANES, electron microscopy and selective extractions. Environmental Science & Technology (In Press).

Burton, E. D., Bush, R. T., Sullivan, L. A., Mitchell, D. R. G. (2008) Schwertmannite transformation to goethite via the Fe(II) pathway: Reaction rates and implications for iron-sulfide formation. Geochimica et Cosmochimica Acta 72, 4551 - 4564.

Burton, E. D., Sullivan, L. A., Bush, R. T., Johnston, S. G., Keene, A. F. (2008) A simple and inexpensive chromium-reducible sulfur method for acid-sulfate soils. Applied Geochemistry 23, 2759 - 2766.

Burton, E. D., Sullivan, L. A., Bush, R. T., Powell, B. (2008) Iron-sulfide and trace element behaviour in sediments of Coombabah Lake, Moreton Bay (Australia). Marine Pollution Bulletin 56, 1353 - 1358.

Burton, E. D., Bush, R. T., Sullivan, L. A., Mitchell, D. R. G. (2007) Reductive transformation of iron and sulfur in schwertmannite-rich accumulations associated with acidified coastal lowlands. Geochimica et Cosmochimica Acta 71, 4456 - 4473.

Burton, E. D., Bush, R. T., Sullivan, L. A. (2006) Sedimentary iron geochemistry in acidic waterways associated with coastal lowland acid sulfate soils. Geochimica et Cosmochimica Acta 70, 5455 - 5468.

Burton, E. D., Bush, R. T., Sullivan, L. A. (2006) Reduced inorganic sulfur speciation in drain sediments from acid-sulfate soil landscapes. Environmental Science & Technology 40, 888 - 893.

Burton, E. D., Bush, R. T., Sullivan, L. A. (2006) Acid-volatile sulfide oxidation in coastal floodplain drains: iron-sulfur cycling and effects on water quality. Environmental Science & Technology 40, 1217 - 1222.

Burton, E. D., Bush, R. T., Sullivan, L. A. (2006) Elemental sulfur in drain sediments associated with acid sulfate soils. Applied Geochemistry 21, 1240 - 1247.