Bioaccumulation and toxicokinetics of polycyclic aromatic compounds and metals in giant floater mussels (Pyganodon grandis) exposed to a simulated diluted bitumen spill

Oil spills constitute a major risk to the environment and the bioaccumulation potential of the derived oil con-stituents will influence their impact on aquatic biota. Here we determined the bioaccumulation potential and toxicokinetic parameters of polycyclic aromatic compounds (PACs) and various selected metals in the giant floater mussels (Pyganodon grandis) following experimental oil spills in a freshwater lake. Specifically, these mussels were exposed ex situ for 25 days to water contaminated with naturally weathered diluted bitumen (dilbit), a form of oil commonly transported through pipelines. We detected greater concentrations of total PAC in mussels ( n-ary sumation PAC44) exposed to dilbit-contaminated water (25.92-27.79 mu gg- 1 lipid, n = 9, at day 25 of the uptake phase) compared to mussels from a control with no exposure to dilbit (average of 2.62 +/- 1.95 mu gg- 1 lipid; +/- SD, n = 17). This study demonstrates the importance of including alkylated PACs when assessing the impacts of an oil spill as the concentration of alkylated PACs in mussel tissue were an order of magnitude higher than their parent counterparts. However, metal accumulation in dilbit-exposed mussels did not exceed the un-exposed controls, suggesting no excess metal accumulation by mussels from a 25-day dilbit exposure. From first -order one-compartment models, mean uptake rate constants (0.78-18.11 L g-1 day-1, n = 29) and bio-concentration factors (log values from 4.02 to 5.92 L kg-1, n = 87) for the 29 individual PACs that accumulated in mussels demonstrated that some alkylated PACs had greater bioaccumulation potential compared to their parent PAC counterpart but for the most part, alkylated and parent PACs had comparable BCF values. Results from this study also demonstrated that giant floater mussels could be used to biomonitor PAC contamination following oil spills as PACs accumulated in mussel tissue and some were still detectable following the 16-day depuration phase. This study provides the largest, most comprehensive set of toxicokinetic and bio-accumulation parameters for PACs and their alkylated counterparts (44 analytes) in freshwater mussels obtained to date.

Automated summary

Oil spills pose a major risk to the environment, and in this study, the bioaccumulation potential and toxicokinetic parameters of polycyclic aromatic compounds (PACs) and metals were investigated in giant floater mussels following experimental oil spills in a freshwater lake. It was found that exposure to diluted bitumen (dilbit)-contaminated water resulted in increased concentrations of PACs in the mussels, but there was no excess accumulation of metals. The study also showed that alkylated PACs had higher bioaccumulation potential compared to their parent PAC counterparts.