"Spéciation du Phosphore dans des Sédiments Aquatiques Optimisation Analytique Application Environnementale"

Abstract

"In this study, sediments samples were collected at three oueds in the north-east Algeria: oued El-Kebir, oued Boumerzoug and oued Rhumel. The mineralogical composition of the sediments was evaluated by X-ray fluorescence and Infrared analysis. The contents of metals Al, Ca, Fe, Mn, organic matter and total phosphorus were determined. Generally, the studied sediments are characterized by an alkaline pH, a high electrical conductivity and significant contents of organic matter. The X-ray fluorescence shows that the main components of the sediment matrix are calcium in major part, iron, silicon and aluminum. The infrared spectra show the presence of carbonates, goethite and Kaolinite. The evaluation of the phosphorus retention in the sediments of the three oueds was assessed by fractionation and adsorption tests. The obtained results show that phosphorus is mainly in inorganic form with prevalence of calcic fraction. The phosphorus retention depends on the samples composition. The sediments of oued El-Kebir retain more phosphorus than those of oued Boumerzoug and Rhumel. In a relation with the sediments composition and the method of phosphorus determination, a phosphorus extraction scheme is proposed in this study by optimizing the used reagents and the operating conditions. By applying this extraction scheme, the spatiotemporal evolution of phosphorus speciation during the year 2012, was studied in the sediments of the rivers which cross Constantine city: oued Rhumel and its tributary Boumerzoug. In the sediments of the two streams, the results show the predominance of the residual fraction and the importance of phosphorus bound to detrital apatite. The evolution of the exchangeable fraction and that related to authigenic apatite depends on the pH of the sediments. The reducible fraction is characterized by a significant spatiotemporal evolution. At the end of the summer period, the contribution of the residual organic fraction is less significant. Spatiotemporal changes in the distribution and the mobility of phosphorus are recorded in the sediments of oued Rhumel. In those of oued Boumerzoug, phosphorus is more mobile in the winter and spring."