The effect of redox potential on the stability of some heavy metals in the bottom sediments of the Gulf of Suez, Egypt

الملخص EN

The relationship between pH and Eh values and the content of some heavy metals in 27 bottom sediments from the Gulf of Suez has been studied.

The sediment samples are mainly composed of carbonate-sand and silt.

Three main factors control the behaviour of the examined metals in sediments.

Factor 1 represents a pH-Eh factor that reveals the influence of redox potential on these metals in sediment.

Carbonates are insoluble at high pH and Eh values and hence the metals in the carbonate debris are stable under such redox conditions.

The strong positive loadings on mud (silt and clay), organic carbon, iron and manganese indicate to the close relationship of these components in the marine environment.

The inverse relationship between these components and pH and Eh, indicates that the decay of organic matter tends to lower the pH of the sedimentsbut not far below pH 7.35and consumes the oxygen, and hence lowers the Eh too.

The process of organic matter decay may release part of the iron and manganese content that is associated with organic debris.

Factor 2 is a pH factor that clearly reveals the relationship of pH with iron, copper, zinc and cobalt.

The increase of pH is associated with similar increases in the content of these metals in sediments.

This factor shows that these metals are more stable in the solid phase under more alkaline conditions.

Factor 3 is a metal-carbonate factor where cadmium, nickel, cobalt and lead are mainly present in the carbonate constituents of the sediments.