Soil microbial response to photo-degraded C₆₀ fullerenes

Recent studies indicate that while unfunctionalized carbon nanomaterials (CNMs) exhibit very low decomposition rates in soils, even minor surface functionalization (e.g., as a result of photochemical weathering) may accelerate microbial decay. We present results from a C₆₀ fullerene-soil incubation study designed to investigate the potential links between photochemical and microbial degradation of photo-irradiated C₆₀. Irradiating aqueous ¹³C-labeled C₆₀ with solar-wavelength light resulted in a complex mixture of intermediate products with decreased aromaticity. Although addition of irradiated C₆₀ to soil microcosms had little effect on net soil respiration, excess ¹³C in the respired CO₂ demonstrates that photo-irradiating C₆₀ enhanced its degradation in soil, with ∼0.78% of 60 day photo-irradiated C₆₀ mineralized. Community analysis by DGGE found that soil microbial community structure was altered and depended on the photo-treatment duration. These findings demonstrate how abiotic and biotic transformation processes can couple to influence degradation of CNMs in the natural environment. - Highlights: • ¹³C enriched C₆₀ fullerene was photo-irradiated for 0, 10, 30, or 60 days before being added to soil microcosms. • Approximately 0.78% of the 60 day irradiated C₆₀ was degraded in soils during incubation. • C₆₀ altered microbial community differently depending on photo-irradiation duration. - Prolonged photo-oxidation of ¹³C enriched labeled C₆₀ fullerene was found to enhance mineralization of the nanomaterials during a 90 day incubation in soil.