Heavy metals fractionation and risk assessment in surface sediments of Qarun and Wadi El-Rayan Lakes, Egypt.

This study establishes a baseline for trace metal speciation in Qarun and Wadi El-Rayan lakes. A five-step sequential extraction procedure was applied for the speciation of the Fe, Mn, Zn, and Cu in sediment samples collected at Qarun and Wadi El-Rayan lakes. Mn and Cu were the most mobile metals, whereas the residue fraction maintained the highest concentrations of Zn and Fe (≈ 60 %).

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 (NH(4)Cl-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.