Role of Ester Sulfate and Organic Disulfide in Mercury Methylation in Peatland Soils

Caroline E. Pierce, Olha S. Furman, Sarah L. Nicholas, Jill Coleman Wasik, Caitlin M. Gionfriddo, Ann M. Wymore, Stephen D. Sebestyen, Randall K. Kolka, Carl P.J. Mitchell, Natalie A. Griffiths, Dwayne A. Elias, Edward A. Nater, Brandy M. Toner

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


We examined the composition and spatial correlation of sulfur and mercury pools in peatland soil profiles by measuring sulfur speciation by 1s X-ray absorption near-edge structure spectrocopy and mercury concentrations by cold vapor atomic fluorescence spectroscopy. Also investigated were the methylation/demethylation rate constants and the presence of hgcAB genes with depth. Methylmercury (MeHg) concentration and organic disulfide were spatially correlated and had a significant positive correlation (p < 0.05). This finding is consistent with these species being products of dissimilatory sulfate reduction. Conversely, a significant negative correlation between organic monosulfides and MeHg was observed, which is consistent with a reduction in Hg(II) bioavailability via complexation reactions. Finally, a significant positive correlation between ester sulfate and instantaneous methylation rate constants was observed, which is consistent with ester sulfate being a substrate for mercury methylation via dissimilatory sulfate reduction. Our findings point to the importance of organic sulfur species in mercury methylation processes, as substrates and products, as well as potential inhibitors of Hg(II) bioavailability. For a peatland system with sub-μmol L–1 porewater concentrations of sulfate and hydrogen sulfide, our findings indicate that the solid-phase sulfur pools, which have a much larger sulfur concentration range, may be accessible to microbial activity or exchanging with the porewater.

Original languageEnglish (US)
Pages (from-to)1433-1444
Number of pages12
JournalEnvironmental Science and Technology
Issue number2
StatePublished - Jan 18 2022

Bibliographical note

Funding Information:
Funding from the National Science Foundation Graduate Research Fellowship supported Caroline Pierce. Funding from the US Department of Energy (DOE) and USDA Forest Service Northern Research Station supported O.S.F. A portion of the work performed at Oak Ridge National Laboratory was sponsored by the DOE Office of Biological and Environmental Research, Office of Science (OBER), as part of the Mercury Science Focus Area which is managed by UT-Battelle LLC for the DOE under contract DE-AC05-00OR22725. We thank Nate Aspelin for assistance with porewater sampling; Michael Ottman, Michelle Natarajan, Trudy Bolin, and Tianpin Wu for beamtime assistance at the APS 9-BM; Yongfeng Hu, Qunfeng Xiao, and Aimee Maclennan for beamtime assistance at the CLS SXRMB; Sona Psarska, Reba Van Beusekom, and Mikhail Mack for assistance with MeHg measurements; and Kevin Ng, Steven Chang, and Haiyong Huang for assistance with the methylation and demethylation rate assays. Funding for the methylation and demethylation rate assays were provided by the Natural Sciences and Engineering Research Council of Canada. Acid volatile sulfur concentrations were measured at the St. Croix Watershed Research Station, Science Museum of Minnesota. A portion of the work was conducted at (1) the APS, a DOE user facility operated for the DOE Office of Science by Argonne National Laboratory under Contract no. DE-AC02-06CH11357, and (2) the CLS, which is supported by the Canadian Foundation for Innovation, Natural Sciences and Engineering Research Council of Canada, the University of Saskatchewan, the Government of Saskatchewan, Western Economic Diversification Canada, the National Research Council Canada, and the Canadian Institutes of Health Research. The SPRUCE experiment is supported by the DOE OBER and is a collaborative research between Oak Ridge National Laboratory and the USDA Forest Service. USDA Forest Service funds support the long-term research program at the Marcell Experimental Forest and the participation of R.K.K. and S.D.S. in this research. N.A.G. was supported by DOE OBER.

Publisher Copyright:
© 2022 The Authors. Published by American Chemical Society


  • methylmercury
  • peatland
  • sulfur XANES

PubMed: MeSH publication types

  • Journal Article
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.


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