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Speciation of aluminum in soils and stream waters: The importance of organic matter

In English

Författare

Summary, in English

Aluminum (Al) is the most common metal in the Earth's crust, and exists mainly in the form of silicates, oxides and hydroxides, or in complexes with natural organic matter (NOM) or inorganic ligands. Since speciation is a key factor for understanding the environmental impact of Al, it is important to determine the chemical forms of Al that predominate in different natural media and under varying geochemical conditions. This study investigated how complexation with NOM influenced the speciation of Al(III) in different environmental samples (isolated aquatic NOM, organic soils and stream waters) using X-ray absorption spectroscopy (XAS) and Infrared (IR) spectroscopy. The combined spectroscopic results showed that Al(III) formed mononuclear complexes with carboxylic functional groups in NOM that were sufficiently stable to suppress the hydrolysis and polymerization of Al(III). These organic Al complexes were favored at slightly acidic pH values between pH 3 and 6 and at decreasing Al concentrations. The XAS results of the organic soils and the stream water samples indicated a variation in the speciation from a predominance of organically complexed Al in the stream waters to a mixture of Al-NOM complexes and precipitated Al phases (Al hydroxides and/or Al silicates) in the organic soils. Although the presented XAS results were limited by relatively low signal-to-noise caused by the low K-edge energy of Al, the combined spectroscopic results provided new and useful information about Al in different environmental samples and showed that NOM and pH are important parameters controlling the speciation of Al. (C) 2015 Elsevier B.V. All rights reserved.

Publiceringsår

2015

Språk

Engelska

Sidor

32-43

Publikation/Tidskrift/Serie

Chemical Geology

Volym

417

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Geochemistry
  • Environmental Sciences

Nyckelord

  • IR spectroscopy
  • XAS
  • Stream water
  • Soil
  • Organic matter
  • Aluminum

Status

Published

Projekt

  • MICCS - Molecular Interactions Controlling soil Carbon Sequestration

Forskningsgrupp

  • Microbial Ecology

ISBN/ISSN/Övrigt

  • ISSN: 0009-2541