Trace element geochemical associations in the Arabian Gulf

Abstract

A sequential extraction procedure is utilized to determine the geochemical fractionation of Cd, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn in surficial sediments from the NW Arabian Gulf. It has been established that there are no strong variations in the concentration of total trace elements among different locations within the studied area. The mean concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn in the lithogenous fraction were 0.19, 88, 25, 5868, 1158, 456, 10, 116 and 33 μg g −1 respectively, whereas in the non-lithogenous fraction they were 0.17, 6.2, 6.78, 1828, 755, 91, 4, 22 and 3 μg g −1 respectively. In the non-lithogenous fraction the easily or freely leachable and exchangeable fraction is not geochemically significant, thus having only 11% Cu, 9% Mn, 2% V and 3% Zn of the total non-lithogenous metals. The carbonates and Fe-Mn oxides and hydroxides fractions appear to be the most dominant phases in the non-lithogenous fraction containing 100% Cd, 35.5% Cr, 50% Cu, 33% Fe, 80% Mn, 40% Ni, 42.5% Pb, 33% V and 45% Zn in the former and 21% Cr, 35% Cu, 59% Fe, 6% Mn, 14% Ni, 57.5% Pb, 35% V and 45% Zn in the latter. This observation has been attributed to the scavenging affinity of Fe-Mn oxides and to the carbonate-rich sediments of the Arabian Gulf. On the other hand, the organics and sulphides fraction contains the following percentages of the total non-lithogenous metals: 43.5% Cr, 4% Cu, 8% Fe, 5% Mn, 46% Ni, 30% V and 7% Zn.