Microbial- and thiosulfate-mediated dissolution of mercury sulfide minerals and transformation to gaseous mercury

Adiari Vázquez-Rodríguez, Colleen M. Hansel, Tong Zhang, Carl Lamborg, Cara M. Santelli, Samuel Webb, Scott Brooks

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Mercury (Hg) is a toxic heavy metal that poses significant human and environmental health risks. Soils and sediments, where Hg can exist as the Hg sulfide mineral metacinnabar (ß-HgS), represent major Hg reservoirs in aquatic environments. Metacinnabar has historically been considered a sink for Hg in all but severely acidic environments, and thus disregarded as a potential source of Hg back to aqueous or gaseous pools. Here, we conducted a combination of field and laboratory incubations to identify the potential for metacinnabar as a source of dissolved Hg within near neutral pH environments and the underpinning (a)biotic mechanisms at play. We show that the abundant and widespread sulfur-oxidizing bacterium Thiobacillus extensively colonized metacinnabar chips incubated within aerobic, near neutral pH creek sediments. Laboratory incubations of axenic Thiobacillus cultures lead to the release of metacinnabar-hosted Hg(II) and subsequent volatilization to Hg(0). This dissolution and volatilization was greatly enhanced in the presence of the sulfur intermediate, thiosulfate, which served a dual role by enhancing HgS dissolution and providing an additional metabolic substrate for Thiobacillus. These findings reveal a new coupled abiotic-biotic pathway for the transformation of metacinnabar-bound Hg(II) to Hg(0), while expanding the sulfide substrates available for neutrophilic chemosynthetic bacteria to Hg-laden sulfides. They also point to mineral-hosted Hg as an underappreciated source of gaseous elemental Hg to the environment.

Original languageEnglish (US)
Article number596
JournalFrontiers in Microbiology
Volume6
Issue numberMAY
DOIs
StatePublished - 2015

Keywords

  • Mercury
  • Mercury sulfide dissolution
  • Metacinnabar
  • Sulfur chemosynthesis
  • Sulfur metabolism
  • Sulfur oxidation
  • Thiobacillus
  • Thiosulfate

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