Iron-Monosulfide Oxidation in Natural Sediments: Resolving Microbially Mediated S Transformations Using XANES, Electron Microscopy, and Selective Extractions

Abstract

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 micromol 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 02 partial pressure of approximately 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 (S8(0)) was a key intermediate S oxidation product Transmission electron microscopy showed the S8(0) to be amorphous nanoglobules, 100-200 nm in diameter. The quantitative importance of S8(0) was confirmed by linear combination XANES spectroscopy, after accounting for the inherent effect of the nanoscale S8(0) particle-size on the corresponding XANES spectrum. Both the selective extraction and XANES data showed that oxidation of S8(0) to SO4(2-) was mediated by microbial activity. In addition to directly revealing important S transformations, the XANES results support the accuracy of the selective extraction scheme employed here.

Review on iron availability in soil: interaction of Fe minerals, plants, and microbes

“…In anaerobic conditions, dissimilatory SO 4 2− reducing bacteria (Desulfotomaculum or Desulfosporosinus) can drive the rapid reductive dissolution of poorly ordered ferric (hydr)oxides, such as ferrihydrite (Stackebrandt et al 1997;Stubner 2002). In addition, sulfidogenesis can also sequester Fe by facilitating the precipitation of Fe-sulfide minerals such as pyrite (Burton et al 2009(Burton et al , 2011. This is one of the most common microbial reactions in anaerobic soils (Fig.…”

Modification of Mackinawite with L-Cysteine: Synthesis, Characterization, and Implications to Mercury Immobilization in Sediment

“…Mackinawite was reported as an effective isolating material for use as a sediment cap (Liu et al, 2009). Although pure mackinawite can immobilize mercury, it has a low stability when exposed to oxidized conditions (Burton et al, 2009;Liu et al, 2008;Wolthers et al, 2005). Under field conditions, the capping material has to be in contact with the oxigenated water column during the capping building.…”

“…Piuille et al (1995) reported that the enzyme pyruvate-ferrodoxin oxyreductase was stable in O 2 (atmospheric air) and the L-cysteine groups seemed to provide the oxidation stability. Some investigators have tested iron sulfide oxidation at environmental pH ranges (Burton et al, 2009;Bourdoiseau et al, 2008). Most of the literature is related to the oxidation of reduced iron sulfide compounds such as pyrite, troilite, and pyrrhotite under acidic conditions, for solving acid mine drainage issues (Moses et al, 2003).…”

“…Mackinawite is considered a precursor to other iron-sulfides (FeS 2 , Fe 1-x S, Fe 1+x S, Fe 3 S 4 ), and should follow the same pattern of oxidation, occurring via intermediate polysulfide species, resulting in FeOOH and elemental S 0 or iron sulfate. Mackinawite oxidation can occur in biotic or abiotic conditions, but is not microbially mediated (Burton et al, 2009). In attempting to improve the oxidation resistance of pyrite, Zhang et al (2003) reported the suppression of pyrite oxidation by about 90%, through the polymerization of diacetylene groups in the lipid tails, producing a cross-linked layer on the mineral surface.…”

Geochemical characteristics of inorganic sulfur in Shijing River, South China

“…8 However, sedimentary sulfide formation and oxidation can cause a rapid deoxygenation and acidification of the overlying water during sediment resuspension, which represents an environmental hazard. [9][10][11] Many procedures have been developed for the determination of acidvolatile sulfur (AVS), elemental sulfur (ES), and chromiumreducible sulfur (CRS) in sediment, and there are many reports of the quantitative measurements of the specificity and efficiency of each procedure for various inorganic and organic sulfur compounds. 3,7 Because it is an important indicator of geochemical processes for the modality of sulfur in sediment, RIS distributions in marine sediment and coastal salt marshes have been estimated.…”