Heavy metals in a contaminated Australian estuary—Dispersion and accumulation trend |
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| Authors: | PS Roy EA Crawford |
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| Institution: | 1. Geological Survey of N.S.W., Department of Mineral Resources, P.O. Box 5288, G.P.O., Sydney 2001 Australia;2. 18 Kameruka Road, Northbridge, N.S.W. 2063 Australia |
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| Abstract: | Very high concentrations of Zn, Pb, Cu and Cd occur in the muddy bottom sediments of Lake Macquarie, a saline coastal lagoon in southeastern Australia. The trace metals emanate from industrial sources, especially a lead-zinc smelter, at the northern end of the lake. Individual metal concentrations decrease progressively away from the source area but at differing rates; Zn is most mobile and Cd appears to be deposited first. They approach natural background levels in the southern part of the lake. Mn shows a reverse trend but Ni, Co, Ag and Fe rarely rise above background levels.Shallow cores in the lake bed penetrated a metal enriched surface zone 15–35 cm thick underlain by uncontaminated sediments with natural (background) metal concentrations. Sedimentation rates determined from radiocarbon ages on shells in the cores mainly range between 0·15 and 0·5 mm yr?1. Over the 85 years since industrialization commenced, less than 5 cm of mud has accumulated on the lake bed. Bioturbation is invoked to account for the depth to which the sediment has been enriched in heavy metals. |
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| Keywords: | heavy metals dispersion estuaries contamination sedimentation rates bioturbation Australia |
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