Does equilibrium passive sampling reflect actual in situ bioaccumulation of PAHs and petroleum hydrocarbon mixtures in aquatic worms?

Over the past couple of years, several analytical methods have been developed for assessing the bioavailability of environmental contaminants in sediments and soils. Comparison studies suggest that equilibrium passive sampling methods generally provide the better estimates of internal concentrations in organisms and thus of subsequent risks. However, field studies to validate the potential of passive sampling to predict actual in situ bioaccumulation are scarce and limited information only exists on selected, individual compounds. The present study investigated whether bioaccumulation of PAH and complex petroleum hydrocarbon mixtures in field-exposed aquatic worms could be predicted properly with passive samplers. To this end, in situ bioaccumulation in aquatic worms at 6 PAH-contaminated locations and 8 petroleum hydrocarbon (oil)-contaminated locations was compared with the results of in situ solid phase micro extraction (SPME) applications. For the oil-contaminated sediments, bioaccumulation was also assessed in the lab with polyoxymethylene solid phase extraction (POM-SPE). Actual PAH bioaccumulation was generally predicted within a factor of 4 with in situ SPME, using temperature-adjusted SPME fiber-water partition coefficients and lab-derived bioaccumulation factors (BAFs) for the worm species used, demonstrating the method's potential under field conditions. In situ SPME appeared to be less suitable for predicting bioaccumulation of oil however, in contrast to POM-SPE in the lab, which assessed in situ oil bioaccumulation within a factor of 3, while also closely reflecting the actual distribution of oil boiling point fractions (the hydrocarbon block profile) as accumulated by the worms. All in all, the results indicated that (specific) equilibrium passive samplers, either applied in the field or the lab, have great potential for assessing bioaccumulation of environmental contaminant mixtures from field-contaminated sediments.