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Mechanisms of Methyl Mercury Net Degradation in Alder Swamps: The Role of Methanogens and Abiotic Processes
Umeå University, Faculty of Science and Technology, Department of Chemistry.ORCID iD: 0000-0001-9570-8738
2018 (English)In: Environmental Science and Technology Letters, E-ISSN 2328-8930, Vol. 5, no 4, p. 220-225Article in journal (Refereed) Published
Abstract [en]

Wetlands are common net producers of the neurotoxin monomethylmercury (MeHg) and are largely responsible for MeHg bioaccumulation in aquatic food-webs. However, not all wetlands net produce MeHg; notable exceptions are black alder (Alnus glutinosa) swamps, which net degrade MeHg. Here we report the mechanisms of MeHg demethylation in one such swamp (EHT), shown to be a sink for MeHg during four consecutive years. The potential demethylation rate constant (k(d) ) in soil incubations was similar to 3 times higher in the downstream (EHT-D: k(d) similar to 0.14 d(-1)) as compared to the upstream part of the swamp (EHT-U: k(d) 0.05 d(-1)). This difference concurred with increased stream and soil pH, and a change in plant community composition. Electron acceptor and inhibitor addition experiments revealed that abiotic demethylation dominated at EHT-U while an additional and equally large contribution from biotic degradation was observed at EHT-D, explaining the increase in MeHg degradation. Biotic demethylation (EHT-D) was primarily due to methanogens, inferred by a decrease in k(d) to autoclaved levels following selective inhibition of methanogens. Though methanogen-specific transcripts (mcrA) were found throughout the wetland, transcripts clustering with Methanosaetaceae were exclusive to EHT-D, suggesting a possible role for these acetoclastic methanogens in the degradation of MeHg.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018. Vol. 5, no 4, p. 220-225
National Category
Environmental Sciences Geochemistry
Identifiers
URN: urn:nbn:se:umu:diva-147312DOI: 10.1021/acs.estlett.8b00081ISI: 000430022300006OAI: oai:DiVA.org:umu-147312DiVA, id: diva2:1206688
Available from: 2018-05-17 Created: 2018-05-17 Last updated: 2018-06-09Bibliographically approved

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Björn, Erik

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CiteExportLink to record
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  • apa
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