PARTITIONING AND COMPLEXATION OF COPPER IN THE FLY RIVER, PAPUA-NEW-GUINEA

A combination of field and laboratory studies have been conducted to examine the role of complexation by dissolved organic matter (DOM) and partitioning onto suspended sediments in controlling the distribution and speciation of copper in the Fly River, Papua New Guinea. The system receives a substantial input of copper, primarily in particulate form, from the Ok Tedi copper mine which is located in the head waters of the river system. Release of dissolved copper from mine-derived particulates is the dominant process occurring in the first 600 km downstream of the mine site after which there is significant attenuation of dissolved copper concentrations through adsorption reactions involving riverine sediments. Speciation measurements show that dissolved copper is present predominantly in the form of DOM complexes. Inorganic copper has a much higher adsorptive affinity for natural particulates than copper complexed with DOM. Adsorption kinetics studies strongly suggest that dissolved and adsorbed copper are not in true thermodynamic equilibrium. The combination of release from mine-derived particles, complexation by organic matter, adsorption onto particulates and disequilibrium between the various forms of copper gives rise to a highly complex system.