Contaminant pathways in Port Curtis: Final report - OzCoasts

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Contaminant pathways in Port Curtis: Final report1: Introduction1.2 Summary of the screening level risk assessmentThe objectives of the Port Curtis screening level risk assessment project were to:(i)(ii)(iii)Review and collate the existing physical, chemical and biological datawith particular reference to contamination of sediments, waters and biotaIdentify data gaps and collect new contaminant data for waters,sediments and biotaIdentify contaminants that pose a risk to humans and the environment, byundertaking a screening level ecological risk assessment (SLERA) and ahuman health risk assessment (HHRA) using the combined data sets(iv) Outline future research needs.A risk assessment framework formulated by the US Environmental ProtectionAgency (USEPA 1998) was utilised. Conceptual models were developed to assistwith planning and design of the study. Following a systematic screening process,aluminium, arsenic, cadmium, copper, chromium, iron, mercury, nickel, lead,selenium, zinc, fluoride, cyanide, polycyclic aromatic hydrocarbons (PAHs) andtributyltin (TBT) were the contaminants examined in detail. Contaminantconcentrations were measured in water and sediments and in biota includingseagrass (Zostera capricorni), oysters (Saccostrea spp.), and mud whelks(Telescopium telescopium). For the HHRA, concentrations of aluminium, arsenic,cadmium, copper, chromium, iron, mercury, nickel, lead, selenium, and zinc weremeasured in fish and shellfish likely to be consumed by humans, namely,barramundi (Lates calcarifer), sea mullet (Mugil cephalus), mud crab (Scyllaserrata) and banana prawns (Penaeus merguiensis). Tributyltin was measured inthe edible flesh of mud crab.The compiled data for water, sediment and biota concentrations was assessedagainst assessment endpoints. For waters and sediments, the chosen endpointswere the latest Australian water and sediment quality guidelines(ANZECC/ARMCANZ 2000). The ability of biota to integrate fluctuatingconcentrations of metals over time and to reflect exposure via dietary uptakeallowed a thorough investigation of the exposure of biota to contaminants in thePort Curtis Estuary. The observed contaminant concentrations in biota at studysites were compared with benchmarks derived from concentrations in biota atcontrol sites and from the literature.For the screening level HHRA, chronic daily intakes (CDIs) of contaminants byadults and children consuming seafood from this region were compared tothreshold toxicity values set by regulatory agencies (ATSDR 2005). To account3
Contaminant pathways in Port Curtis: Final report1: Introductionfor additivity of other chemicals, a hazard quotient greater than 0.1 indicated acontaminant of potential concern (COPC).The following contaminants of potential ecological concern were identified:• TBT in waters• Arsenic, TBT and naphthalene (based on limited historical data) insediments.Particulate arsenic and naphthalene may be derived from natural sources withinPort Curtis (e.g. oil shale deposits). The main sources of tributyltin werecommercial shipping and the leisure boats that historically utilise the area.TBT contamination is a problem affecting all large commercial ports. TBTconcentrations are expected to decline in Port Curtis over the next decade asthis antifoulant is completely phased out worldwide.The concentrations of dissolved metals in waters of the Port Curtis Estuary werebelow levels of regulatory concern. However, the concentrations of dissolvedcopper, nickel, lead and zinc were elevated relative to concentrations at pristinecoastal water sites in Australia. The reasons for these elevated concentrationsmay be industrial discharges or natural inputs of metals from local geologicalformations.The concentrations of metals in sediments were generally below levels ofregulatory concern. However, arsenic, chromium and nickel concentrations wereconsistently above the ANZECC/ARMCANZ (2000) low interim sediment qualityguideline trigger values at many sites, which does not necessarily implydeleterious effects but is a trigger for further investigations. The concentrationsof arsenic, chromium and nickel were comparable to those at control sites,suggesting natural sources.The concentrations of aluminium, arsenic, copper, chromium, iron, mercury, nickel,selenium and zinc were significantly enriched in marine biota sampled within PortCurtis relative to organisms at reference sites. This indicates that marineorganisms living in Port Curtis are exposed to higher metal concentrations (ascompared to pristine coastal locations). This did not necessarily imply adverseeffects resulting from exposure to elevated concentrations. It was noted thatfurther studies were required to investigate whether organism health is impairedby these increased body burdens of metals.The spatial analysis conducted as part of the SLERA indicated that the CalliopeRiver and mid-harbour regions of Port Curtis contain the highest concentrations ofcontaminants.4
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