Major and trace metals of the nearshore sediments of Farasan Islands, southern Red Sea, Saudi Arabia

Abstract

The Farasan Islands (FI) are coral-group islands located in the southern Red Sea platform of Saudi Arabia. Thirty nine sediment samples were collected from nearshore of the FI and investigated in regard to their major and trace metals. The concentration trends of metals were in the following order: Ca>Mg>K>Fe>Cu>Mn>Cd>Pb>Zn>Ni indicating typical warm, marine overprints for these metals with dominance of high-Mg calcite. The PCA indicated that the Ca, Mg and K were the dominant metals in the nearshore sediments of the FI. The concentrations of Fe and Mn showed unexpected low values (450 ± 434 and 12.2 ± 9) in comparison with those of the eastern Red Sea coast. However, Cu concentration is similar to that of the Red Sea lagoonal system. Anthropogenic activities were noted in the Khor As Sailah embayment as indicated by high concentration peaks of Fe, Mn, K, Cu, Cd, Ni and Pb. The R-mode hierarchical clustering divided the metals and sediments into 4 associations. The associations of Cd–K–Pb–Cu and Sand–CaCO3 are independent from the influence of OC and sediment grain size and they could be derived from biogenic substances. The Mud-Fe–Mn–Ni–OC indicated a high adsorptive capacity of mud and OC for heavy metals. The Ca–Mg–Zn-Gravel highlighted the indiscriminate interference of Mg2+ and Zn2+ ions into the lattice of calcite or the effect of bacteria and algal biosorption on the fixation of heavy metals. The metals in the FI are independent of riverine inputs, so they could be used as a natural background for metals in the nearshore sediments of the Red Sea.