Comparison of Two Methods for the Fractionation of Phosphorus from Sediments of the Lower Oum Rabiaa Basin (Morocco)

This study concerns the characterization of the phosphorus from the sediments of the lower Oum Rabiaa basin (Morocco), characterized by three dams in series (Imfout, Daourat and Sidi Maachou). Two fractionation methods, Bonzongo et al. (1989) and Golterman (1996), were tested in the present study in order to assess the mobile and biologically available fractions. The obtained results demonstrate a substantial difference between the sampled sediments. The presence of three dams in series is responsible for the distribution of phosphorus in the sediments of this section by reducing phosphorus contributions to endorsement. The speciation of phosphorus of sediment shows that the phosphorus was principally present in inorganic form; the fraction Ca-P was higher than that of the Fe-P. In relative terms (% P-fraction in relation to Total-P), the sampled sediments have very similar behaviour, the quantitative differences between samples being strongly correlated to their total phosphorus content. The two methods tested did not give the same results, especially not for the measurement of Fe-P and Ca-P. The Fe-P extracted with the Golterman method using specific chelators was higher than extracted with Bonzongo et al. (1989) using NaOH after an extraction of organic phosphate using H sub(2)O sub(2). Regarding the Ca-P fraction, the results obtained with the Bonzongo method were higher. These differences have serious consequences when the mobile pools of phosphate in sediments are estimated.