Fate of radiolabeled C₆₀ fullerenes in aged soils

Fullerenes (e.g. C₆₀, C₇₀, etc.) present in soil may undergo changes in its retention with aging. In this study, the partitioning behavior of (¹⁴C)-C₆₀ aged up to 12 weeks was investigated in biosolids-amended soil. Spiked samples were subjected to sequential partitioning using water, methanol, and toluene followed by total combustion of solids; the distribution of ¹⁴C across solvents and matrices were used to provide insights on C₆₀ behavior. In most samples, ¹⁴C only partitioned in toluene with the remaining (non-extractable) activity detected in the solid phase. In all biosolids-amended soil samples, an increase in non-extractable ¹⁴C were observed for those exposed to light (vs dark) with the greatest difference observed in biosolids + sand samples. Possible processes that contribute to the observed ¹⁴C distribution, i.e. retention and potential transformation of C_60, were discussed. Over-all, results suggest that environmental exposure to C₆₀ and potentially transformed C₆₀ species, as a result of their release from soils, is likely to be low.