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

A combination of field and laboratory studies have been conducted to e xamine 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 syste m receives a substantial input of copper, primarily in particulate for m, from the Ok Tedi copper mine which is located in the head waters of the river system. Release of dissolved copper from mine-derived parti culates is the dominant process occurring in the first 600 km downstre am of the mine site after which there is significant attenuation of di ssolved copper concentrations through adsorption reactions involving r iverine sediments. Speciation measurements show that dissolved copper is present predominantly in the form of DOM complexes. Inorganic coppe r has a much higher adsorptive affinity for natural particulates than copper complexed with DOM. Adsorption kinetics studies strongly sugges t that dissolved and adsorbed copper are not in true thermodynamic equ ilibrium. The combination of release from mine-derived particles, comp lexation by organic matter, adsorption onto particulates and disequili brium between the various forms of copper gives rise to a highly compl ex system.