Bioconcentration and bioaccumulation of C 60 fullerene and C 60 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 C ₆₀ 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 C ₆₀ fullerene and its main transformation product, [6,6]C ₆₀ O epoxide, were studied to the mentioned organisms employing analyses by liquid chromatography coupled to high-resolution mass spectrometry. Our results show that C ₆₀ fullerene and its [6,6]C ₆₀ O present a low bioconcentration factor (BCF) to biofilms: BCF _C60  = 1.34 ± 0.95 L/kg _dw and BCF _C60O  = 1.43 ± 0.72 L/kg _dw . 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]C ₆₀ O 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 C ₆₀ fullerenes in their organism (BAF _C60  = 2670 ± 3070 L/kg _dw ; BAF _C60O  = 1330 ± 1680 L/kg _dw ), 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.
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