Observations on heavy metal geochemical association in marine sediments of the Jordan Gulf.of Aqaba

Abstract

The geochemical fractionation of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in surface sediments from the northeastern portion of the Gulf of Aqaba has been determined by the use of a sequential extraction procedure. The results obtained indicate that there are variations in the concentrations of trace elements among the selected locations within the study area. In the lithogenous (L) fraction, the mean concentrations of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were 1.1, 10.3, 47.6, 2.6, 6775, 112.6, 19.0, 32.5, and 16.5 μg g −1 respectively. In the non-lithogenous (NL) fraction the exchangeable or easily leachable fraction is geochemically insignificant, being less than 9% of the total non-lithogenous fraction. The carbonate-bound fraction appears to be the least dominant phase in the non-lithogenous fraction. By comparison the Fe-Mn oxides-bound fractions are the most dominant phases in the non-lithogenous fraction containing 65–83% Cd, 38–88% Co, 20–79% Cr, 61–80% Cu, 47–80% Ni, 36–82% Pb, 66–73% Zn, 36–74% Mn, and 23–60% Fe. This is attributed to the strong scavenging capabilities of Fe-Mn oxides to many trace elements. The organic fraction of the sediments contains the next highest percentage of trace elements as it contains the following percentages of the total non-lithogenous metals: 0–10% Cd, 0–58% Co, 8–80% Cr, 14–36% Cu, 0–47% Ni, 0–57% Pb, 19–35% Zn, 18–64% Mn, and 39–77% Fe. The variations are due to the type and grain size of sediments; organic matter contents; distance and location of the sampling site from the major sources of pollution.