Chemical Speciation of Dissolved Copper Controlled by Dissolved Organic Matter in Hypersaline Coastal Waters of Kuwait Bay

Copper (Cu) is a biologically important trace metal in marine environments, and its chemical speciation is strongly influenced by interactions with dissolved organic matter (DOM), which can significantly regulate its bioavailability and toxicity. A chemical speciation study of dissolved Cu by adsorptive stripping voltammetry in conjunction with the characterization of DOM by UV-Vis spectrophotometer in the coastal hypersaline waters of Kuwait Bay was carried out in this study. DOM exhibited strong Cu-binding capacity, forming thermodynamically stable Cu-DOM complexes with Log K values ranging from 11.5 ± 0.3 to 14.4 ± 0.5 in the study area. Chemical speciation parameters of Cu-DOM complexes varied with proxies for humic acid (HA) and fulvic acid (FA) concentrations, and with increasing molecular weight of the DOM. These findings suggest that both autochthonous and allochthonous organic matter play vital roles in binding dissolved Cu and controlling Cu2+ ion concentrations (an indicator of bioavailable Cu) in the coastal waters of the northwestern Arabian Gulf off Kuwait.