Phosphorus and organic matter in wetland sediments: analysis through gel permeation chromatography (GPC)

Issue		Agron. Sustain. Dev. Volume 20, Number 5, July-August 2000 Nature and functions of the organic matter in the environment


Page(s)		567 - 576
DOI		10.1051/agro:2000151

DOI: 10.1051/agro:2000151

Agronomie 20 (2000) 567-576

Phosphorus and organic matter in wetland sediments: analysis through gel permeation chromatography (GPC)

Rodolphe Gilbin - Elena Gomez - Bernadette Picot

Département Sciences de l'Environnement et Santé Publique, UMR CNRS 5556, Faculté de Pharmacie, 15 av. Ch. Flahault, 34060 Montpellier Cedex 2, France

(Received 20 September 1999; revised 29 February 2000; accepted 16 May 2000)

Abstract:

Sequential extraction defines fractions of phosphorus of distinct natures and properties in sediments. The organic fraction is partially characterised, sometimes regarded as refractory and stable in spite of variations observed in situ. The unidentified fractions are generally judged complex forms associated with the humic substances. The organic forms of phosphorus were extracted by alkaline solution, following extraction of the inorganic and hydrolysable organic forms in an acid solution. In the sediment of an eutrophic coastal lagoon, organic phosphorus extracted with NaOH accounts for 18% of total phosphorus and 79% of the organic fraction. In order to better characterise the organic phosphorus in the sediments, the GPC chromatography technique was used. Thus several distinct organic fractions were observed: condensed humic acids, with a low phosphorus content, and molecules of molecular compactness, such as fulvic acid which contains the majority of the phosphorus.

Keywords: phosphorus / organic matter / sediment / wetland / gel permeation chromatography

Résumé:

Interactions du phosphore et de la matière organique dans le sédiment d'une zone humide. Des extractions séquentielles permettent de définir des fractions de phosphore de nature et de propriétés distinctes dans les sédiments. La fraction organique est partiellement caractérisée, parfois considérée comme réfractaire et stable malgré des variations quantitatives observées in situ. Les fractions non identifiées sont généralement assimilées à des formes complexes associées aux substances humiques. Des formes organiques du phosphore ont été extraites par une solution alcaline, après extraction des formes inorganiques et des formes organiques hydrolysables en milieu acide. Dans le sédiment d'une lagune côtière eutrophe, elles représentent 18 % du phosphore total et 79 % de la fraction organique. Dans le but de mieux caractériser la nature du phosphore organique des sédiments, nous avons utilisé la technique de chromatographie de perméation sur gel. Ceci a permis de définir plusieurs fractions organiques distinctes : des acides humiques condensés contenant peu de phosphore et des molécules de plus faible encombrement moléculaire, de type acide fulvique, contenant la majorité du phosphore.

Mots clé : phosphore / matière organique / sédiment / zone humide / chromatographie de perméation sur gel

Communicated by Isabelle Lamy

Correspondence and reprints: Bernadette Picot
dsesp@crit.univ-montp2.fr

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