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Project details

Title: Derwent Estuary Study 1992-1994
Id: 197
Acronym: Derwent Estuary Study
Investigator(s): John Hunter
(Former) CSIRO Division of Oceanography - Hobart [details]

Description (full): The history of development along the shores of Hobart's Derwent estuary made the river and bay system a natural choice for study by CSIRO's Coastal Zone Program. Contaminants such as metals and organic compounds have been accumulating for much of this century from the effluent discharges of industrial and urban activities. By the 1970s, the community was alarmed at the state of the river: chemical analyses indicated dangers to human health from eating filter-feeding shellfish such as oysters; some metals were above levels recommended by the National Health and Medical Research Council; some beaches were dangerously polluted. In a detailed study by CSIRO's Division of Marine Research in 1992, chemists took water samples at the surface, near the bottom and sometimes in between every three months for nearly two years. The surveys provided a clear indication of inputs of some metals such as zinc, mercury and cadmium to surface waters in the middle reaches of the estuary. However, the input of most of these trace metals appeared to have decreased over the last 20 years. Pulp fibre is the main major source of organic pollutant in the upper estuary, and sewage in the middle and lower reaches. A method of tracing sewage-derived organics by using biomarkers, which was developed for the Sydney Outfall and Port Phillip Bay studies, is also being used in the Derwent. High concentrations of sewage have been detected where the river opens up into the estuary. Biomarker techniques have also shown that stormwater is a major source of hydrocarbons entering the estuary as either road run-off or industrial effluent. While physical modelling creates a picture of the estuary's dynamics, the nature of most chemical processes is that in reality they will behave differently in different environments and often cannot be treated as inert substances transported by the river currents. To accommodate this, the next stage of study by CSIRO is to link a model that predicts the behaviour of the chemical substances in an estuary to the physical models. The linked models will not only predict the movement of water and particles but will also include data on chemical processes in aquatic systems and the factors influencing chemical reactivity. To validate this model, scientists use advanced analytical techniques that provide accurate measurements of trace elements and chemical compounds referenced to baseline levels in unpolluted aquatic systems. This is the barometer against which the potential for chronic damage to an ecosystem is also measured.
Years: 1992 to 1994
Remarks: WWW page available at

List of surveys that this project was on.

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Survey InvestigatorDescription
Derwent Estuary Survey (1992-1994)

J. Hunter (CSIRO) As part of the CSIRO Coastal Zone Program, a multi-disciplinary study was undertaken of the Derwent Estuary in SE Tasmania, including a comprehensive suite of physical and chemical observiations and their incorporation into models of the hydrodynamics and the fate of chemical compounds in terms of sources, sinks, transport and reactivities.
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