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Sammanfattning

Despite the societal demand for restoring drained boreal peatlands, a firm understanding of how drainage and restoration (through rewetting) affect the biogeochemistry of these ecosystems is missing. In addition to the intended ecosystem services, restoration may result in undesired effects and potential environmental threats, such as mercury (Hg) methylation. It is important to note that prolonged drainage can alter the peat properties, which makes the effects of restoration difficult to predict.This thesis evaluates how drainage and restoration impact physical and chemical peat properties and net methylmercury (MeHg) formation. For each drained and restored peatland, a corresponding undisturbed natural reference peatland was sampled. Each peatland was sampled to a depth of 50 cm and analysed for carbon (C), nitrogen (N), δ13C, δ15N, organic matter content (OM), and dry bulk density (BD). The restored peatlands (and the natural peatlands) involved additional measurements of sulphur (S) XANES, along with the groundwater level and concentrations of inorganic mercury (IHg) and MeHg.Peatland drainage was found to significantly alter the physical and chemical peat properties. The drained and restored peatlands, when compared with natural reference peatlands, were characterised by increased BD and C and N contents in OM, along with decreased OM contents, C:N ratios, and δ13C. Despite restoration efforts, the groundwater level of the restored peatlands remained five centimetres deeper than what was observed for natural reference peatlands. Although restoration failed to replicate the water table levels and redox conditions in natural peatland sites, the drainage and subsequent restoration increased concentrations of IHg and MeHg, as well as %MeHg of total Hg. The cumulative mass of MeHg and IHg in the top 50 cm of peat also increased after drainage and restoration. Thus, increasing the risk of MeHg and IHg export from peatlands to adjacent streams and lakes.

Nyckelord

boreal peatlands; peatland restoration; peat properties; carbon cycle; nitrogen cycle; peat decomposition; mercury methylation

Publicerad i

Acta Universitatis Agriculturae Sueciae
2025, nummer: 2025:27
Utgivare: Swedish University of Agricultural Sciences

SLU författare

UKÄ forskningsämne

Skogsvetenskap
Miljövetenskap
Multidisciplinär geovetenskap

Publikationens identifierare

  • DOI: https://doi.org/10.54612/a.2dd04kk3ti
  • ISBN: 978-91-8046-462-8
  • eISBN: 978-91-8046-512-0

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/132967