Occurrence of copper-complexing ligands in the coastal sediments of eastern Red Sea

The speciation of copper in seawater is greatly influenced by the presence of organic ligands that find their way from various sources. The occurrence of copper-complexing ligands in the coastal sediment of eastern Red Sea and their potential resuspension under the impact of physical parameters such as wind and currents are investigated. The competitive ligand exchange and detection of copper by adsorptive cathodic stripping voltammetry (ACSV) were used to determine the dissolved concentration of copper-complexing ligands and their conditional stability constants after suspension of marine sediments in UV-irradiated seawater. The laboratory experiments of suspended marine sediments in UV-irradiated seawater followed by the measurements of copper in the filtrate have indicated the presence of two ligands with concentrations in the range of 3.53–25.58 nM g−1 for L1 and 8.33–28.35 nM g−1 for L2 whereas the log conditional stability constants ranged between 12.59 and 13.87 for log K 1 and 11.79 and 12.96 for log K 2. Comparison of log K 2 with values for log K of copper complexes with thiols from previous studies suggests that thiols consist of the major part of copper-complexing ligands in the coastal marine sediments of eastern Red Sea. Relatively, positive and good correlations are found for copper-complexing ligands with total copper and organic content in the sediments. Calculation of the flux of copper-complexing ligands and their contribution to the total budget in the coastal water south of Jeddah indicate that the impact of sediments as potential source is less than 13 %. It is therefore that other processes such as in situ production and input from sewage effluents have to be considered to account for the majority of dissolved copper-complexing ligands in the area.