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Research article - Peer-reviewed, 2021

Biogeochemical influences on net methylmercury formation proxies along a peatland chronosequence

Wang, Baolin; Zhong, Shunqing; Bishop, Kevin; Nilsson, Mats B.; Hu, Haiyan; Eklof, Karin; Bravo, Andrea G.; Akerblom, Staffan; Bertilsson, Stefan; Bjorn, Erik; Skyllberg, Ulf;

Abstract

A geographically constrained chronosequence of peatlands divided into three age classes (young, intermediate and old) was used to explore the role of biogeochemical influences, including electron donors and acceptors as well as chemical speciation of inorganic mercury (Hg(II)), on net formation of methylmercury (MeHg) as approximated by the fraction of MeHg to total mercury (THg) in the peat soil. We hypothesized that removing vascular plants would reduce availability of electron donors and thus net MeHg formation. However, we found no effect of the vascular plant removal. The sum of the potential electron donors (acetate, lactate, propionate and oxalate), the electron donation proxy organic C/Organic N, and the potential electron acceptors (Fe(III), Mn and sulfate) in porewater all showed significant correlations with the net MeHg formation proxies in peat soil (MeHg concentration and %MeHg of THg). Thus differences in both electron donor and acceptor availability may be contributing to the pattern of net MeHg formation along the chronosequence. In contrast, Hg(II) concentrations in peat porewater showed small differences along the gradient. A chemical speciation model successfully predicted the solubility of Hg and MeHg in the porewater. The modeling pointed to an enhanced concentration of Hg-polysulfide species in the younger peatlands as a potential factor behind increased Hg(II) solubility and methylation in the more nutrient-rich peatlands. This work contributes to the understanding of Hg and MeHg cycling in peatlands which can help guide mitigation measures to reduce aquatic MeHg biomagnification in peatland dominated landscapes. (C) 2021 The Authors. Published by Elsevier Ltd.

Keywords

Mercury; Methylmercury; Chronosequence; Peatland; Porewater; Hg solubility; Chemical speciation

Published in

Geochimica et Cosmochimica Acta

2021, volume: 308, pages: 188-203
Publisher: PERGAMON-ELSEVIER SCIENCE LTD

Authors' information

Zhong, Shunqing
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Åkerblom, Staffan
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Wang, Baolin
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Bjorn, Erik
Umea University
Guiyang Institute of Geochemistry, CAS
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment
Bravo, Andrea G.
CSIC - Instituto de Ciencias del Mar (ICM)
Zhong, Shunqing
Hengyang Normal University
Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment

Associated SLU-program

Non-toxic environment

UKÄ Subject classification

Geochemistry

Publication Identifiers

DOI: https://doi.org/10.1016/j.gca.2021.06.010

URI (permanent link to this page)

https://res.slu.se/id/publ/113799