Bioaccumulation of perfluorinated alkyl acids in two benthic invertebrates: Lumbriculus variegatus and Chironomus riparius

The aim of this work was to study the bioaccumulation of 3 perfluorinated alkyl acids (PFBS, PFOS and PFOA) in two benthic invertebrates: Lumbriculus variegatus and Chironomus riparius. Specimens of Lumbriculus variegatus and larvae of Chironomus riparius were exposed to microcosms with formulated sediment and water at nominal concentration of 10 ?g/L. The distribution of the perfluorinated acids in the different compartments (overlaying water, sediment and organisms) at the end of the tests have been measured. Most of the added PFOA and PFBS were measured in the overlaying water (65%) whereas PFOS was mainly detected in the sediment (36 % of the added amount). No loss of PFOA was detected for evaporation while PFBS and PFOS were partially air stripped (25% and 45 % respectively) because of the aeration of the microcosms. Accumulation was higher in L. variegatus than in C. riparius for all the 3 perfluorinated alkyl acids. Accumulation in C. riparius were mainly due to uptake by aqueous phase: the bioaccumulation factors (BAF) based on water concentrations were 0.2, 3 and 19 ?g kg-1 ww/?g L-1 for PFBS, PFOA and PFOS respectively. On the contrary sediment ingestion was the main uptake route for L. variegatus: bioaccumulation is also dependent on the organic carbon content of the sediment that affects feeding rate of L. variegatus. The BAF based on sediment concentrations were 32, 55 and 47 ?g kg-1ww/?g kg-1dw for PFBS, PFOA and PFOS respectively. PFBS is potentially less bioaccumulable than its homologues with longer carbon chain because of its shorter carbon chain and its higher solubility. Nevertheless our results showed that, in sediment-dwelling organisms, bioaccumulation of PFBS can be of the same order of magnitude of that measured for PFOS. This result raises new questions about the environmental risk of this compound.