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XAS study of iron speciation in soils and waters from a boreal catchment

Author:
  • Anneli Sundman
  • Torbjorn Karlsson
  • Hjalmar Laudon
  • Per Persson
Publishing year: 2014
Language: English
Pages: 93-102
Publication/Series: Chemical Geology
Volume: 364
Document type: Journal article
Publisher: Elsevier

Abstract english

Iron (Fe) is a key element, strongly influencing the biogeochemistry of soils, sediments and waters, but the knowledge about the variety of Fe species present in these systems is still limited. In this work we have used X-ray absorption spectroscopy (XAS) to study the speciation of Fe in soils and waters from a boreal catchment in northern Sweden. The aim was to better understand the controls of Fe speciation across different, but adjacent landscape elements including soil, soil solution, groundwater and stream water draining catchments with contrasting land characteristics. Our results showed that all samples contained mixtures of Fe(II) and Fe(III). The soils consisted of Fe phyllosilicates, Fe (hydr) oxides and Fe complexed by natural organic matter (NOM). All aqueous samples contained Fe(II)- and Fe(III)-NOM complexes, often in combination with Fe(III) (hydr) oxides that were associated with NOM. The variation in contribution from Fe-NOM and Fe (hydr) oxides was controlled by pH and total concentrations of NOM. The XAS spectra suggested formation of mononuclear Fe-NOM complexes consisting of chelate ring structures, but it could not be determined whether they originated solely from Fe(III)- or from a mixture of Fe(II)/Fe(III)-NOM complexes. Our collective results showed that the Fe speciation was highly variable across the different landscape elements and streams. This variation was manifested both in the distribution between mononuclear Fe-NOM complexes and Fe (hydr) oxides associated with NOM and between Fe(II) and Fe(III). These results highlight the complexity of Fe speciation in natural environmental systems and thus the challenges in interpreting Fe reactivity. (C) 2013 Elsevier B.V. All rights reserved.

Keywords

  • Earth and Related Environmental Sciences
  • Fe speciation
  • XAS
  • Stream water
  • Soil solutions
  • Ground water
  • Krycklan
  • catchment

Other

Published
  • MICCS - Molecular Interactions Controlling soil Carbon Sequestration
  • ISSN: 0009-2541
Per Persson
E-mail: per [dot] persson [at] biol [dot] lu [dot] se

Professor

MEMEG

+46 46 222 17 96

+46 70 266 38 79

E-C350

50

Professor

Centre for Environmental and Climate Research (CEC)

+46 46 222 17 96

+46 70 266 38 79

D350

Ekologihuset, Sölvegatan 37, Lund

50