Source of heavy metals in sediments of the Port Jackson estuary, Australia

The Port Jackson estuary has a highly urbanised and industrialised catchmen t and is central to Sydney, which with a population of approximately 4 mill ion, comprises almost a quarter of Australia's population. The estuary has a long history of contamination which has resulted in extensive areas of po lluted sediments mainly associated with the most industrialised/commerciali sed parts of the catchment. The highest concentrations of sedimentary heavy metals occur at the headwaters of embayments and tributaries in the estuar y, especially in the central city region where gradients decline rapidly aw ay from canals. High total suspended solids, elevated concentrations of hea vy metals in sediment and in particulates in canals draining large catchmen ts are evidence that drainage from these areas is a major source of contami nants to this estuary. Another possible important point source of heavy met als is leachates from reclamation areas, whereas licenced polluters do not impact on a regional scale. Of the diffuse sources, atmospheric contributio ns may be substantial, but storm water drains with small catchments and sew er overflows have no observable impression on the regional distribution of heavy metals in surficial sediments. Biological effects criteria suggest th at heavy metal concentrations in sediments are sufficiently high to adverse ly affect biota over large areas of Port Jackson. Large volumes of contamin ated sediment and a continuing supply of heavy metals to the estuary will m ake remediation difficult. (C) 1999 Elsevier Science B.V. All rights reserv ed.