Bioconcentration and bioaccumulation of C60 fullerene and C60 epoxide in biofilms and freshwater snails (Radix sp.).

Fullerenes are carbon nanomaterials that have awaken a strong interest due to their adsorption properties and potential applications in many fields. However, there are some gaps of information about their effects and bioconcentration potential in the aquatic biota. In the present work, freshwater biofilms and snails (Radix sp.) were exposed to fullerene C60 aggregates, at concentrations in the low μg/L order, in mesocosms specifically designed to mimic the conditions of a natural stream. The bioconcentration factors of C60 fullerene and its main transformation product, [6,6]C60O epoxide, were studied to the mentioned organisms employing analyses by liquid chromatography coupled to high-resolution mass spectrometry. Our results show that C60 fullerene and its [6,6]C60O present a low bioconcentration factor (BCF) to biofilms: BCFC60 = 1.34 ± 0.95 L/kgdw and BCFC60O = 1.43 ± 0.72 L/kgdw. This suggests that the sorption of these aggregates to biota may be less favoured than it would be suggested by its hydrophobic character. According to our model, the surface of fullerene aggregates is saturated with [6,6]C60O molecules, which exposes the polar epoxide moieties in the surface of the aggregates and decreases their affinity to biofilms. In contrast, freshwater snails showed a moderate capacity to actively retain C60 fullerenes in their organism (BAFC60 = 2670 ± 3070 L/kgdw; BAFC60O = 1330 ± 1680 L/kgdw), probably through ingestion. Our results indicate that the bioaccumulation of these carbon nanomaterials can be hardly estimated using their respective octanol-water partition coefficients, and that their colloidal properties, as well as the feeding strategies of the tested organism, play fundamental roles.