Dissolved trace metal distributions in Port Jackson estuary (Sydney Harbour), Australia

Concentrations of dissolved metals (Cd, Cu, Ni, Mn and Zn) were determined for summer and winter, under low-flow conditions in Port Jackson, a microtidal, well-mixed estuary in south-east Australia. Mean concentrations of Cd (0.04±0.02 µg/l), Ni (0.86±0.40 µg/l), Mn (20.0±25 µg/l) and Zn (6.47±2.0 µg/l) were below water quality guidelines. Concentrations of Cu (1.68±0.37 µg/l), however, slightly exceeded recommended values. Dissolved Ni and Mn behaved mostly conservatively, whereas Cd, Cu and Zn showed mid-estuarine maxima. Peaks in Cd, Cu and Zn concentrations were located in the upper estuary, independent of the salinity and suspended particulate matter loading, and were consistent with anthropogeni- c inputs of metals in the estuary. Concentrations of dissolved Cu were highest in summer, whereas concentrations of Cd, Ni and Mn were significant- ly lower in summer than winter (P[le ]0.05). The increase in temperature and biological activity during summer explained the seasonal variation. The sequence of log Kd values (20-30 salinity) was Mn > Zn > Cu > Ni. These results give unique information concerning the contemporaneous distribution of dissolved trace metals in the Port Jackson estuary and they provide a data set against which the long-term contamination may be assessed.