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Scientific article
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Identification of stoichiometric iron-phosphorus colloids produced in a eutrophic lake

Published inAquatic sciences, vol. 61, no. 2, p. 133-149
Publication date1999
Abstract

Iron-rich colloids formed at the oxic-anoxic interface of a eutrophic lake (Lake Lugano; CH) were characterized by bulk chemical methods and analytical electron microscopy. Fractionation of raw waters showed that non-dissolved iron is particulate above the oxicline and mainly colloidal in the anoxic part of the hypolimnion, while non-dissolved ortho-phosphate is mostly colloidal through the water column. Because of these differences, filtration did not prove helpful for the determination of the role of iron-rich species in the scavenging of ortho-phosphate. On the other hand, analytical electron microscopy revealed that iron-rich nano-granules (ca. 50nm) are associated to the surface of bacterially produced fibrillar polysaccharides. Iron colloids in these complex entities contain important and constant amounts of phosphorus ([PO4]part:[Fe]part = 0.48 ± 0.11, n = 1096 Fe-rich entities analyzed by electron microscopy), which suggests that phosphates are stoichiometrically incorporated into the hydrous iron oxide phase, with a tentative composition Fe2[OOH]1-x[(OH)3]x[PO4], during its genesis.

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Keywords
  • Aquatic colloids
  • Iron
  • Phosphorus
  • Stoichiometric composition
  • Nutrient scavenging
  • Electron microscopy
Citation (ISO format)
LIENEMANN, Charles-Philippe et al. Identification of stoichiometric iron-phosphorus colloids produced in a eutrophic lake. In: Aquatic sciences, 1999, vol. 61, n° 2, p. 133–149. doi: 10.1007/s000270050058
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ISSN of the journal1015-1621
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