Sequential fractionation of phosphorus in sediments of El-Fayum lakes—Egypt

The amounts and forms of potentially mobile phosphorus (P) in surface sediments of Qarun and Wadi El-Rayan lakes were evaluated during winter and summer using a sequential chemical extraction. Five sedimentary P fractions were separately quantified: loosely sorbed P (NH₄Cl-P), iron-associated P (BD-P), calcium- bound P (HCl-P), metal oxide bound P (NaOH-P), and residual P (organic and refractory P). The results indicated that the fractional composition of the examined lakes was different while the total P concentrations were approached. The inorganic P in the surface sediment mainly consisted of Ca-P followed by Fe-P in Qarun Lake, while Al-P took the second order in Wadi El-Rayan lakes. The ranks order of the different P extracts were HCl-P > residual-P ≈ NaOH-P > NH₄Cl-P > BD-P and residual-P > NH₄Cl-P > HCl-P > NaOH-P > BD-P for Qarun and Wadi El-Rayan lakes, respectively.