Geochemical cycling and speciation of copper in waters and sediments of Macquarie Harbour, Western Tasmania

The factors determining the concentration and speciation of copper in the waters and sediments of Macquarie Harbour, Tasmania were investigated. This harbour is the most extensively copper-contaminated estuarine water body in Australia owing to current and historical inputs of metal-rich waters and sediments from the nearby Mount Lyell copper mine. The dissolved copper concentrations in the harbour water column were highly variable (4–560 μg l −1) and displayed a north to south gradient, decreasing with distance from the King River, which carries the inputs from the mine. The most significant process affecting dissolved copper concentrations was the neutralisation of acidic river waters with seawater and the resulting coprecipitation with iron oxyhydroxide flocs. Approximately 60% of the riverine dissolved copper input was removed from solution by this process. Particulate copper concentrations in surficial benthic sediments were high in most regions of the harbour (typically 0.5–1 mg g −1). In the north, sediments were dominated by fine, mine-derived material and showed uniform particulate copper concentrations with depth. Sediment acid-volatile sulphide concentrations were highest (11–142 μmol g −1) in the southern harbour and were barely detectable in the northern harbour region (