Sorption of Buckminsterfullerene (C60) to Saturated Soils

With the increasing use of C60 in many industrial and commercial sectors, it is likely that it will eventually appear in the environment however, its environmental fate and transport is still largely unknown. The extent to which C60 partitions to soil will contribute to its environmental fate and bioavailability. Because C60 is extremely hydrophobic, in this study the distribution between soil and mixtures of ethanol (EOH) and water were measured at ethanol mole fractions ranging from X(EOH) = 1.0-0.4 for two soils. By measuring K(p) at X(EOH) = 1.0 for a series of soils that ranged in organic carbon and clay mineral content, possible mineral contribution to the overall partition process was found for some of the soils. After correcting for any mineral contribution to sorption, the organic carbon normalized partition coefficient, K(oc), at each value of X(EDH) was calculated from the measured K(p) values. Through a classical thermodynamic relationship, the K(oc) values determined at X(EOH) = 1.0-0.4 were extrapolated to estimate the pure water (i.e., X(EOH) = 0) K(oc) value of 10(7.1) (L/kg). Accounting for any dissolved organic matter (DOM) in any pure water-soil mixtures may lower this estimate by over a factor of 2, placing this estimate in good agreement with C60's octanol-water partition coefficient, K(ow) (= 10(6.7)).