Opposing spatial trends in methylmercury and total mercury along a peatland chronosequence trophic gradient

Abstract

Peatlands are abundant elements of boreal landscapes where inorganic mercury (IHg) can be transformed into bioaccumulating and highly toxic methylmercury (MeHg). We studied fifteen peatlands divided into three age lasses (young, intermediate and old) along a geographically constrained chronosequence to determine the role of biogeochemical factors and nutrient availability in controlling the formation of MeHg. In the 10 cm soil layer just below the average annual growing season water table, concentrations of MeHg and %MeHg (of total Hg) were higher in younger, more mesotrophic peatlands than in older, more oligotrophic peatlands. In contrast, total mercury (THg) concentrations were higher in the older peatlands. Partial least squares (PLS) analysis indicates that the net MeHg production was positively correlated to trophic demands of vegetation and an increased availability of potential electron acceptors and donors for Hg methylating microorganisms. An important question for further studies will be to elucidate why there is less THg in the younger peatlands compared to the older peatlands, even though the age of the superficial peat itself is similar for all sites. We hypothesize that ecosystem features which enhance microbial processes involved in Hg methylation also promote Hg reduction that makes previously deposited Hg more available for evasion back to the atmosphere. (C) 2020 Elsevier B.V. All rights reserved.

Keywords

Peatland; Mercury; Methylation; Methylmercury; Chronosequence

Published in

Science of the Total Environment
2020, volume: 718, article number: 137306
Publisher: ELSEVIER

SLU Authors

• Wang, Baolin

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

• Nilsson, Mats

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

• Eklöf, Karin

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

• Ehnvall, Betty

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

• Åkerblom, Staffan

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

• Bertilsson, Stefan

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    
  • Uppsala University

• Skyllberg, Ulf

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

• Bishop, Kevin

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

Associated SLU-program

Acidification

Global goals (SDG)

SDG6 Clean water and sanitation

UKÄ Subject classification

Environmental Sciences

Publication identifier

• DOI: https://doi.org/10.1016/j.scitotenv.2020.137306

Permanent link to this page (URI)

https://res.slu.se/id/publ/105392