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Per Persson. Foto.

Per Persson

Dekan

Per Persson. Foto.

Ectomycorrhizal Fungal Transformation of Dissolved Organic Matter : Consequences for Reductive Iron Oxide Dissolution and Fenton-Based Oxidation of Mineral-Associated Organic Matter

Författare

  • Lelde Krumina
  • Michiel Op De Beeck
  • Viktoriia Meklesh
  • Anders Tunlid
  • Per Persson

Summary, in English

Recent studies have shown that dissolved organic matter (DOM) decomposed by ectomycorrhizal (ECM) fungi increases adsorptive properties of organic matter towards soil mineral surfaces. Concomitantly, ECM fungi secrete secondary metabolites with iron reducing capacity that are thought to participate in non-enzymatic Fenton-based decomposition of DOM. The aim of this study was to investigate if the iron reduction induced by the ECM fungus Paxillus involutus during organic matter decomposition was conserved in the decomposed DOM. We explored how the modified DOM reductively dissolved ferrihydrite and goethite nanoparticles and how these processes affected the reactions with H2O2 and the Fenton-based oxidation of mineral-associated organic matter. Culture filtrates were obtained from incubation of the ECM fungus on DOM from forest litter of a spruce forest. This modified DOM was separated by extraction into an ethyl acetate and a water fraction. These fractions were reacted with ferrihydrite and goethite in absence and presence of H2O2. Dissolved Fe2+ and HO• were measured and the reactions at the iron oxide-water interfaces were monitored in real-time with in-situ IR spectroscopy. Experiments showed that decomposition of DOM by P. involutus generated a modified DOM that displayed an increased and persistent reductive capacity. Most of the reductants were isolated in the aromatic- and carboxyl-dominated ethyl acetate fraction but some reduction capacity was also captured in the water fraction mainly containing carbohydrates. Reductive dissolution was more extensive for ferrihydrite than goethite, and this process generated significant oxidation of the DOM-ferrihydrite associations. Oxidation of adsorbed DOM was triggered by H2O2 via heterogenous and homogeneous Fenton reactions. These oxidation processes were favored by ferrihydrite because of a high reduction potential and a high efficiency of heterogeneous Fenton as compared to goethite. An optimal timing between the heterogeneous and homogeneous Fenton processes triggered extensive radical oxidation of the DOM-ferrihydrite associations generating a high concentration of surface-associated oxalate. Overall, the results show that organic matter associated with ferrihydrite may be more susceptible to radical oxidation than on goethite, and that fungal decomposition of DOM in general may have consequences for other important soil processes such as mineral dissolution, adsorption and initiation of radical reactions.

Avdelning/ar

  • Centrum för miljö- och klimatvetenskap (CEC)
  • Mikrobiologisk ekologi
  • BECC: Biodiversity and Ecosystem services in a Changing Climate
  • MEMEG
  • Fysikalisk kemi

Publiceringsår

2022-04-26

Språk

Engelska

Publikation/Tidskrift/Serie

Frontiers in Earth Science

Volym

10

Dokumenttyp

Artikel i tidskrift

Förlag

Frontiers Media S. A.

Ämne

  • Geochemistry

Nyckelord

  • dissolved organic matter (DOM)
  • Fenton reactions
  • ferrihydrite
  • goethite
  • hydroxyl radicals
  • infrared spectroscopy
  • Paxillus involutus
  • reductive dissolution

Status

Published

Forskningsgrupp

  • Microbial Ecology

ISBN/ISSN/Övrigt

  • ISSN: 2296-6463