Humic substances in the sediments of lake Edku, Egypt : II-its role in the accumulation of trace metals

الملخص AR

-Humic and fulvic acids extracted from Lake Edku sediments are highly enriched in Cu, Zn and Ni and to small extentin Co when compared to the bulk sediment, but depleted in Feand Mn.

The mean concentrations of Cu, Ni, Zn and Co in the humic acid extract were, 359, 208, 188 and 47 p,g g~ 1 while their concentrations in the bulk sediment were 65, 84, 129 and 40 (jcg g _ 1 respectively.

Humic acid showed relatively higher concentrations for all elements except Zn.

The presence of humic acid in solution enhances the transfer of Cu, Cd, Ni and Zn into the suspended matter at pH's higher than 6, through the precipitation of metal-humic acid complexes and adsorption on freshly precipitated humic acid.

Fe showed another mechanism which, most probably, is the formation of colloidal hydrous oxides.