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Improving risk assessment and remediation rests on better understanding of contaminant bioavailability. Despite their strong toxicological attributes, little is known about the partitioning behaviour and bioavailability of polar polycyclic aromatic hydrocarbons (PAHs) in aquatic environments. The present study provides an insight into the bioavailable fractions of polar PAHs and their parent analogues in the tissues of the Sydney rock oyster, Saccostrea glomerata, a model aquatic bio-indicator organism. The concentration and distribution patterns of parent and polar PAHs including oxygenated PAHs (oxyPAHs), nitrated PAHs (NPAHs) and heterocyclic PAHs (HPAHs) were determined in water, sediment and oysters from an ecologically and economically important estuary of New South Wales, Australia. Total concentrations of PAHs, oxyPAHs, NPAHs and HPAHs were higher in sediments compared to oyster tissue and water. For most polar PAHs, total concentrations for water, sediment and oyster samples were less than 1 µg/g (µg/l for water) while parent PAH concentrations were several orders of magnitude higher. Computed biota-sediment accumulation factors (BSAFs) on lipid-normalized oyster concentrations revealed that while ∑oxyPAHs and ∑HPAHs exhibited low accumulation from sediment to oyster tissues (BSAF < 1), ∑PAHs and ∑NPAH were found to be accumulated at high levels (BSAF > 1). BSAF individual computation showed that bioaccumulation of nine investigated HPAHs in oyster tissues were relatively low and only 2-EAQ (oxyPAH ) and 1N-NAP (NPAH) showed high levels of accumulation in oyster tissues, similar to parent PAHs. To the best of our knowledge, this is the first known study on the bioavailability of polar and non-polar PAHs in an Australian aquatic environment. The outcome of this study might be a useful indicator of the potential risks of polar PAHs to humans and other living organisms.

Increasing our understanding of the bioavailable fractions of polycyclic aromatic compounds (PACs) in an aquatic environment is important for the assessment of the environmental and human health risks posed by PACs. More importantly, the behaviour of polar polycyclic aromatic hydrocarbons (polar PAHs), which are metabolites of legacy PAHs, are yet to be understood. We, therefore, carried out a study involving Sydney rock oysters (Saccostrea glomerata) sourced from two locations, that had been exposed to PAH contamination, within an Australian southeast estuary. Biomonitoring of these oysters following relocation from the estuary to a relatively isolated waterway was done at 24 and 72 h after deployment, and subsequently at 7, 14, 28, 52 and 86 days. Control samples from Camden Haven River were sampled for PAC analyses just before deployment, after 28 days and at the end of the study (day 86). Lipid-normalised concentrations in oyster tissues across the 86-day sampling duration, elimination rate constants (k2), biological half-lives (t1/2), and time required to reach 95% of steady-state (t95), were reported for parent PAHs and the less-monitored polar PAHs including nitrated/oxygenated/heterocyclic PAHs (NPAHs, oxyPAHs and HPAHs) for the three differently sourced oyster types. Most of the depurating PAHs and NPAHs, as well as 9-FLO (oxyPAH), had k2 values significantly different from zero (p < 0.05). All other oxyPAHs and HPAHs showed no clear depuration, with their concentrations remaining similar. The nondepuration of polar PAHs from oyster tissues could imply greater human health risk compared to their parent analogues.