Behavior of phosphorus in the sediment of Oum Er-Biaa estuary (Morocco - Atlantic)
The study of the estuary of Oum er-Biâa, located on the moroccan atlantic near the Azemmour city, far 60 km in the south of Casablanca, focus on the hydrogeochemical behavior of phosphorus. In the sediment of the estuary of Oum er-Biâa, total phosphorus was mainly in mineral form (76%-95%), with a predominance of the fraction related to calcium (45%-90%), that was in apatitic form and not mobilizable. The ferric fraction P-Fe (2%-38%) contributed mainly to the biodisponibility of phosphorus in this estuary. The temporal and spatial variations of this fraction were controlled on the one hand, by the characteristics of the sediment (particule fraction < 63 μm and organic matter) and, on the other hand, by the salinity. Indeed, the upstream muddy zone rich in organic matter had a high capacity to uptake the phosphorus (P-Fe and ROP) in march and july. In the downstream sandy zone, the magnetite presented a great importance for the adsorption of phosphorus, specially at high salinity during may and october.