Distribution and behaviour of some heavy metals in the surface sediments of al-Arbaeen lagoon, Jeddah, Red Sea Coast

Abstract EN

-Analysis of surface sediments from Al-Arbaeen Lagoon shows that the sediments consist mainly of soft mud that is dark in colour, rich in organic matter, and associated with high concentrations of hydrogen sulphide.

These characteristics indicate that the lagoon basin is a low energy, anoxic, sulphidic sedimentary environment.

The concentrations of Fe, Mn, Zn, Pb, Ni, Cr, Co, Cu and organic carbon are higher in the lagoon sediments than the background levels of these elements measured in remote unpolluted marine sediments This is due to the large input of anthropogenic waste into the lagoon.

Data indicate that the behaviour of Fe, Mn, Co and Cr are strongly influenced by redox reactions and seem to exist as sulphide minerals such as pyrite or are associated with iron sulphide minerals.

Zn and Cu show a preferential association with the organic carbon.

Ni and Pb do not show any definite association with different geochemical phases of the sediments.

Diagenetic remobilization of some metals and precipitation with iron sulphide minerals and organic carbon appear to be the possible mechanisms explaining the heterogeneous distribution of these metals produced by redox reactions in the lagoon’s surface sediments.