Stereoselective Bioaccumulation of Water and Soil-Associated Dufulin Enantiomers in Tubifex

In this study, the stereoselective bioaccumulation of rac-dufulin, pure S-(+)-dufulin, and pure R-(-)-dufulin in Tubifex (Oligochaeta, Tubificida) were analyzed in spiked-water and spiked-soil systems at low and high dose levels. In the bioaccumulation experiments treated with rac-dufulin, the enantioselective behaviors of the enantiomers show that the concentrations of R-(-)-dufulin are higher than those of S-(+)-dufulin at two dose levels. However, when treated with solely pure S-(+)-dufulin and R-(-)-dufulin, no significant difference of concentrations was detected in Tubifex. Furthermore, the calculated accumulation factors in Tubifex indicated that dufulin (racemic or the pure enantiomers) in the spiked-soil treatments had higher bioaccumulation potential than in the spiked-water treatments. The spiked-soil experiments revealed that the dissipation of dufulin in soil was not enantioselective at the enantiomer levels and Tubifex could reduce the concentrations of dufulin in the underlying solid matrix and accelerate its repair and detoxification process.