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Methylmercury formation in boreal wetlands in relation to chemical speciation of mercury(II) and concentration of low molecular mass thiols

Liem-Nguyen, Van and Skyllberg, Ulf and Bjorn, Erik (2021). Methylmercury formation in boreal wetlands in relation to chemical speciation of mercury(II) and concentration of low molecular mass thiols. Science of the Total Environment. 755 , 142666
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Abstract

Methylmercury (MeHg) is a neurotoxin formed from inorganic divalent mercury (Hg-II) via microbial methylation, and boreal wetlands have been identified as major sources of MeHg. There is however a lack of studies investigating the relationship between the chemical speciation of Hg-II and MeHg formation in such environments, in particular regarding to role of thiol compounds. We determined Hg-II methylation potentials, k(meth), in boreal wetland soils using two Hg-II isotope tracers: Hg-198(OH)(2)(aq) and Hg-II bonded to thiol groups in natural organic matter, Hg-200(II)-NOM(ads), representing Hg-II sources with high and low availability for methylation. The Hg-198(OH)(2)(aq) tracer was consistently methylated to a 5-fold higher extent than Hg-200(II)-NOM(ads), independent of environmental conditions. This suggests that the concentration of Hg-II in porewater was a decisive factor for Hg-II methylation. A comprehensive thermodynamic speciation model (including Hg-II complexes with inorganic sulfide (H2S), polysulfides (H2Sn), thiols associated with natural organic matter (NOM-RSH) and specific low molecular mass thiols (LMM-RSH) provided new insights on the speciation of Hg-II in boreal wetland porewaters, but did not demonstrate any clear relationship between k(meth) and the calculated chemical speciation. In contrast, significant positive relationships were observed between k(meth) and the sum of LMM thiol compounds of biological origin. We suggest two possible mechanisms underlying these correlations: 1) LMM thiols kinetically control the size and composition of the HgII pool available for microbial uptake, and/or 2) LMM thiols are produced by microbes such that the correlation reflects a relation between microbial activity and MeHg formation. (C) 2020 The Author(s). Published by Elsevier B.V.

Authors/Creators:Liem-Nguyen, Van and Skyllberg, Ulf and Bjorn, Erik
Title:Methylmercury formation in boreal wetlands in relation to chemical speciation of mercury(II) and concentration of low molecular mass thiols
Series Name/Journal:Science of the Total Environment
Year of publishing :2021
Volume:755
Article number:142666
Number of Pages:9
Publisher:ELSEVIER
ISSN:0048-9697
Language:English
Publication Type:Journal article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Environmental Sciences (social aspects to be 507)
Keywords:Mercury methylation, Soil, Bioavailability, Thermodynamics, Kinetics
URN:NBN:urn:nbn:se:slu:epsilon-p-110349
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-110349
Additional ID:
Type of IDID
DOI10.1016/j.scitotenv.2020.142666
Web of Science (WoS)000600786700069
ID Code:21819
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Ecology and Management
Deposited By: SLUpub Connector
Deposited On:01 Feb 2021 13:23
Metadata Last Modified:01 Feb 2021 13:31

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