Synchrotron X-ray absorption spectroscopy reveals antimony sequestration by reduced sulfur in a freshwater wetland sediment
William W. Bennett A C , Kerstin Hockmann B , Scott G. Johnston B and Edward D. Burton BA Environmental Futures Research Institute, Griffith School of Environment, Griffith University Gold Coast campus, Qld 4215, Australia.
B Southern Cross Geoscience, Southern Cross University, Lismore, NSW 2480, Australia.
C Corresponding author. Email: w.bennett@griffith.edu.au
Environmental Chemistry 14(6) 345-349 https://doi.org/10.1071/EN16198
Submitted: 5 December 2016 Accepted: 6 July 2017 Published: 28 November 2017
Journal Compilation © CSIRO 2017 Open Access CC BY-NC-ND
Environmental context. Antimony is an environmental contaminant of increasing concern, due to its growing industrial usage in flame retardants, lead alloys, glass, ceramics and plastics. Here we show, using X-ray absorption spectroscopy, that antimony may be trapped in wetland sediments by reduced sulfur. This finding has implications for the management and remediation of wetlands contaminated with antimony.
Abstract. The biogeochemistry of antimony (Sb) in wetland sediments is poorly characterised, despite their importance as contaminant sinks. The organic-rich, reducing nature of wetland sediments may facilitate sequestration mechanisms that are not typically present in oxic soils, where the majority of research to date has taken place. Using X-ray absorption spectroscopy (XAS), we present evidence of antimony speciation being dominated by secondary antimony–sulfur phases in a wetland sediment. Our results demonstrate that, by incorporating a newly developed SbIII–organic sulfur reference standard, linear combination fitting analysis of antimony K-edge XAS spectra and robust statistical assessment of fit quality allows the reliable discrimination of SbIII coordination environments. We found that a contaminated wetland sediment in New South Wales, Australia, contained 57 % of the total antimony as SbIII–phases, with 44 % present as a highly-disordered antimony phase, likely consisting of SbIII complexed by organic sulfur (e.g. thiols) or an amorphous SbIII sulfide (e.g. SbS3). The methodological approach outlined in this study and our identification of the importance of reduced sulfur in sequestering antimony has implications for future research in the area of antimony biogeochemistry, and for the management of both natural and artificial wetlands contaminated with antimony.
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