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

Sequential extraction defines fractions of phosphorus of distinct natures a nd properties in sediments. The organic fraction is partially characterised , sometimes regarded as refractory and stable in spite of variations observ ed in situ. The unidentified fractions are generally judged complex forms a ssociated with the humic substances. The organic forms of phosphorus were e xtracted by alkaline solution, following extraction of the inorganic and hy drolysable organic forms in an acid solution. In the sediment of an eutroph ic coastal lagoon, organic phosphorus extracted with NaOH accounts for 18% of total phosphorus and 79% of the organic fraction. In order to better cha racterise the organic phosphorus in the sediments, the GPC chromatography t echnique was used. Thus several distinct organic fractions were observed: c ondensed humic acids, with a low phosphorus content, and molecules of molec ular compactness, such as fulvic acid which contains the majority of the ph osphorus.