HYDROLOGY, SEDIMENTOLOGY AND THE FATE AND DISTRIBUTION OF COPPER IN MINE-RELATED DISCHARGES IN THE FLY RIVER SYSTEM, PAPUA-NEW-GUINEA

Sediments from mined overburden and ore residues are discharged to the Ok Tedi, a tributary of the Fly River system and the largest of Papua New Guinea's rivers. The sediments are enriched with copper. About 60% of the input has a particle size of < 100 μm and is transported as a suspended-load throughout the entire length of the river, a distance of over 1000 river kilometers. Upon reaching the coast, the sediments are deposited in the quieter coastal waters. The water chemistry of the system is dominated by calcium and bicarbonate ions, leading to little variation in the pH of water in the river channels. These factors, together with high dissolved organic carbon and high alkalinity, dominate the distribution coefficient of copper in the system. The copper associated with the sediments largely remains in particulate form in the river system. Laboratory experiments show that, in the estuarine environment, some release of copper is likely. © 1990.