Assessing bioaccumulation behaviour of hydrophobic organic contaminants in a tropical urban catchment

The bioaccumulation behaviour of halogenated flame retardant (HFRs), synthetic musks (SMs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in plankton, invertebrates and fish was assessed in an urban catchment in Singapore which is a tropical island country highly populated. The studied contaminants ranged widely in physical-chemical properties, with K_OW values ranging between approximately 10³-10¹¹. BDE-47 and dechlorane plus (DPs) were the predominant HFRs, while galaxolide (HHCB) and tonalide (AHTN) were the predominant synthetic musk compounds in biota from the studied freshwater system. Concentrations of organochlorine contaminants such as chlordanes, DDE, DDD, PCB 138 and PCB 153 were generally higher than those of the HFRs and SMs. On a wet weight basis, bioaccumulation factors (BAFs) of the current use HFRs were in some cases higher than the bioaccumulation criteria value of 5000 L/kg wet weight. Conversely, BAFs of SMs were found to be less than the 5000 L/kg guideline. Lipid adjusted BAFs (L/kg lipid) of the studied contaminants varied among the different aquatic species, which is likely due to organism trophic level and metabolic transformation capacity differences. BAFs were highly correlated with the chemical K_OW values. For fish, log BAFs of the studied contaminants increased with increasing log K_OW, between a log K_OW range of approximately 3-7, after which BAFs subsequently decreased. A similar relationship was observed for BAFs in the studied invertebrates. For plankton, a simple linear regression was observed between log BAF and log K_OW over the target analyte K_OW range (log K_OW's between 3-11). Predicted BAF values derived from a mechanistic bioaccumulation model for hydrophobic organic contaminants were generally consistent with the observed BAFs. However, in some cases the model substantially overestimated bioaccumulation potential based on the chemical's hydrophobicity, which may be due to a high degree of biotransformation of those compounds. The study provides important information regarding bioaccumulation potential of several emerging organic contaminants of concern.