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

Hagvall, Kristoffer; Persson, Per LU and Karlsson, Torbjorn (2015) In Chemical Geology 417. p.32-43
Abstract
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
IR spectroscopy, XAS, Stream water, Soil, Organic matter, Aluminum
in
Chemical Geology
volume
417
pages
32 - 43
publisher
Elsevier
external identifiers
  • wos:000365098800004
  • scopus:84944058930
ISSN
0009-2541
DOI
10.1016/j.chemgeo.2015.09.012
project
MICCS - Molecular Interactions Controlling soil Carbon Sequestration
language
English
LU publication?
yes
id
10607b3f-276a-45f5-9fd4-4df16b46651e (old id 8370671)
date added to LUP
2015-12-17 11:31:30
date last changed
2017-11-19 03:03:58
@article{10607b3f-276a-45f5-9fd4-4df16b46651e,
  abstract     = {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.},
  author       = {Hagvall, Kristoffer and Persson, Per and Karlsson, Torbjorn},
  issn         = {0009-2541},
  keyword      = {IR spectroscopy,XAS,Stream water,Soil,Organic matter,Aluminum},
  language     = {eng},
  pages        = {32--43},
  publisher    = {Elsevier},
  series       = {Chemical Geology},
  title        = {Speciation of aluminum in soils and stream waters: The importance of organic matter},
  url          = {http://dx.doi.org/10.1016/j.chemgeo.2015.09.012},
  volume       = {417},
  year         = {2015},
}