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Per Persson. Foto.

Per Persson

Dekan

Per Persson. Foto.

High sulfate concentration enhances iron mobilization from organic soil to water

Författare

  • Caroline Björnerås
  • Martin Škerlep
  • Dimitrios Floudas
  • Per Persson
  • Emma S. Kritzberg

Summary, in English

Widespread increases in iron (Fe) concentrations are contributing to ongoing browning of northern freshwaters, but the driver/s behind the trends are not known. Fe mobilization in soils is known to be controlled by redox conditions, pH, and DOC availability for complexation. Moreover, high sulfate concentrations have been suggested to constrain Fe in transition from soil to water, and declining sulfate deposition to have the opposite effect. We studied the effect of these Fe mobilization barriers in a microcosm experiment, applying high (peak S deposition) and low (present day) sulfate treatments and oxic versus anoxic conditions to boreal (O horizon) soil slurries. We hypothesized that anoxic conditions would favor Fe release. On the contrary we expected high sulfate concentrations to suppress Fe mobility, through FeS formation or by lowering pH and thereby DOC concentrations. Anoxia had positive effects on both Fe and DOC concentrations in solution. Contrasting with our hypothesis, Fe concentrations were enhanced at high sulfate concentrations, i.e. increasing acidity in high sulfate treatments appeared to promote Fe mobilization. Establishment of the basidiomycete fungus Jaapia ochroleuca in the oxic treatments 44 days into the experiment had a major impact on Fe mobilization by increasing total Fe concentrations in solution. Thus, anoxia and acidity, along with fungi mediated mobilization, were important in controlling Fe release from soil to the aqueous phase. While Fe is often assumed to precipitate as Fe(oxy)hydroxides in the transition from anoxic to oxic water in the riparian zone, Fe from anoxic treatments remained in solution after introduction of oxygen. Our results do not support reduced atmospheric S deposition as a driver behind increasing Fe concentrations in boreal freshwaters, but confirm the importance of reducing conditions—which may be enhanced by higher soil temperature and moisture—for mobilization of Fe across the terrestrial-aquatic interphase.

Avdelning/ar

  • BECC: Biodiversity and Ecosystem services in a Changing Climate
  • Molekylär ekologi och evolution
  • Enhet akvatisk ekologi
  • Centrum för miljö- och klimatvetenskap (CEC)
  • Akvatisk ekologi

Publiceringsår

2019-09

Språk

Engelska

Sidor

245-259

Publikation/Tidskrift/Serie

Biogeochemistry

Volym

144

Issue

3

Dokumenttyp

Artikel i tidskrift

Förlag

Springer

Ämne

  • Soil Science

Nyckelord

  • Boreal soil
  • Brownification
  • Dissolved organic carbon
  • Iron biogeochemistry
  • Jaapia ochroleuca
  • Reduced atmospheric S deposition

Status

Published

Projekt

  • MICCS - Molecular Interactions Controlling soil Carbon Sequestration

Forskningsgrupp

  • Molecular Ecology and Evolution Lab
  • Aquatic Ecology

ISBN/ISSN/Övrigt

  • ISSN: 0168-2563