Technical Report No. 6
Dr Jochen Müller, Renee Muller, Katrina Goudkamp, Dr Munro Mortimer
Department of the Environment and Heritage, May 2004
ISBN 0 642 54998 2
This study was a component of the National Dioxins Program tasked to quantify and assess the concentrations and relative chemical compositions of dioxin-like chemicals in Australia’s aquatic environment.
The project involved the collection and analysis for dioxin-like chemicals in aquatic sediment cores from 62 sampling locations. Collections were made by a team of sampling personnel using a standard sampling protocol, from locations representative of major catchments based on the National Pollution Inventory. The study was deliberately designed to avoid collecting samples in immediate proximity to known or likely sources of contamination with dioxin-like chemicals. A range of samples was collected from each of freshwater, estuarine and marine locations. Where practical, samples were collected from locations within the same catchment from the non-impacted upper catchment through estuary to marine environment, covering different land-use influences classified as remote, agricultural and urban/industrial. In addition to sediment samples, bivalve samples were collected, when available from the locations from which sediment samples were collected. Fish were also obtained through local commercial fishing industries with an emphasis on local catch of table species.
Chemical analysis of sediment and biota samples was conducted by the Australian Government Analytical Laboratories (AGAL), and a series of quality assurance/quality control (QA/QC) procedures were incorporated into the study, including replicate sampling, replicate analysis and an interlaboratory comparison of analysis using an overseas laboratory highly regarded for its experience in the analysis of dioxin-like chemicals in environmental samples. The QA/QC procedure suggested that the reproducibility of the chemical analysis was good, and that the identification of individual dioxin-like chemicals and quantification of their concentrations in sediment samples was reliable. The analysis of sampling replicates, or samples collected at different sites within the same water body representing similar exposure to dioxin-like chemicals, demonstrated that the greatest uncertainty in the results is likely to relate to variability at specific sampling locations rather than uncertainty in chemical analysis.
The concentrations of dioxin-like chemicals in the sediment and biota samples were assessed both in terms of the concentrations of PCDD/PCDF and PCB and their toxic equivalents. In addition, the patterns of component chemicals were evaluated, and assessments of concentration and patterns were made with respect to geographic location and land-use types.
Dioxin-like chemicals were found in all Australian aquatic sediments analysed, with middle bound concentrations ranging from 0.002 to 520 pg TEQ g-1 dm. Highest concentrations were found in the sediments sampled from the Parramatta River estuary (100 and 520 pg TEQ g-1 dm) and the western section of Port Jackson (78 and 130 pg TEQ g-1 dm), in close proximity to historical manufacturing point sources around Homebush Bay. In addition, elevated concentrations were also found in other estuarine waters of Sydney (Botany Bay) as well as the estuaries in or near Brisbane, Melbourne, Hobart, Perth and Wollongong.
Considering all sediment samples, the median concentrations were 0.2, 2.3 and 0.12 pg TEQ g-1 dm in sediments from freshwater, estuarine and marine locations, respectively. However, statistical analysis showed that median concentrations across marine, freshwater and estuarine sampling locations did not differ significantly. By contrast, urban/industrial sampling locations had significantly greater concentrations of dioxin-like chemicals than samples from remote and agricultural locations. It is also noteworthy that the elevated concentrations in urban/industrial areas were also evident if data were expressed on a total organic carbon basis.
Homologue and congener profiles for the PCDD/PCDF were strongly dominated by OCDD with the 1,2,3,4,6,7,8-heptachloro dibenzodioxin usually the congener with the second highest concentration. The source or formation processes by which such a higher chlorinated dominance could occur remains unresolved despite intensive studies by others. For most sediment samples, PCDD/PCDF dominated the mixture of dioxin-like chemicals present, accounting for more than 80% of the total TEQ. However, a range of samples such as those from the Brisbane River, the Torrens River or from Western Australia showed contributions of PCB exceeding 50%. This suggests local sources of PCB have influenced the compound profiles at those sampling locations.
The middle bound concentrations of dioxin-like chemicals in 18 bivalves samples ranged from 0.0043 pg TEQ g-1 fm to about 1.2 pg TEQ g-1 fm when expressed using fish toxic equivalent factors, with the greatest concentrations in samples from Port Jackson and the Yarra estuary.
Dioxin-like chemicals were also analysed in 23 fish samples from around the country and middle bound concentrations ranged from 0.0053 pg TEQFISH g-1 fm to about 0.49 pg TEQFISH g-1 fm. The level of dioxin-like chemicals was highest in a fish sample obtained from the Sydney/Port Jackson area.
Overall, the results from this study showed that the concentrations of dioxin-like chemicals in the aquatic environment (sediments, bivalves and fish) are in most cases less than published levels for other industrialised countries. However, the concentrations in sediments at a few areas and particularly in the lower Parramatta estuary and the western part of Port Jackson are substantially elevated. The bivalve results followed a similar pattern to the sediment results confirming the existence of areas with elevated environmental exposure levels of dioxin-like chemicals. However, the fish analysed in this study were unaffected, with consistently low levels of dioxin-like chemicals found.