From 6-8 December 2011 a CSIRO team collected water and sediment samples to determine the concentrations of trace metals in Port Curtis, Gladstone, Queensland.
The sampling – conducted midway between neap and spring tides, and while dredging was underway in the Harbour – provides a three-day snapshot only and does not take into account water quality changes over time or at other times.
This study, funded by the Gladstone Ports Corporation, was independently carried out by CSIRO and used very sensitive monitoring and analysis techniques that are able to determine the actual concentrations of many metals in the Harbour.
CSIRO conducted a previous similar study in Gladstone Harbour in 2004/5 which enabled some comparison of results.
CSIRO’s report found:
- No evidence of increased dissolved metal concentrations in the areas of Port Curtis that are being dredged.
- The concentrations of dissolved arsenic, cadmium, cobalt, chromium, copper, manganese, nickel, lead and zinc were below the ANZECC/ARMCANZ marine water quality guideline trigger values that apply in Australia at all 21 sites sampled and the concentrations were relatively low compared to other industrialised harbours.
- Dissolved aluminium concentrations were above the ANZECC/ARMCANZ (2000) environmental concern level (ECL) of 0.5 µg/L at the majority of sites sampled. It should be noted that there is no reliable guideline value for aluminium in marine waters in Australia and the ECL value is a highly conservative value based on very limited toxicity data. There are no water quality guidelines that apply for aluminium in marine waters in Europe or North America. From the current data set, it was not possible to attribute a specific source of the dissolved aluminium.
- Dissolved copper and nickel concentrations were higher in December 2011 compared to previous CSIRO surveys in 2004/5.
- Total metal concentrations in the seafloor sediment samples were below ANZECC guideline values for all metals (where guidelines apply) apart from arsenic.
- Few identifiable trends in concentrations across the Harbour, which means that no hot spots of high metal concentrations were found.
- Metals in suspended sediments were not elevated.
Dredging Today Staff, May 9, 2012; Image: westernbasinportdevelopment