Enantioselective bioaccumulation and degradation of sediment-associated metalaxyl enantiomers in Tubifex tubifex.

Knowledge about the enantioselective bioavailability of chiral pesticides in aquatic organisms facilitates more accurate interpretation of their environmental behaviors. In this study, the enantioselective bioaccumulation of metalaxyl enantiomers in Tubifex tubifex was detected in two uptake pathways. For the spike water treatment, a 16 day exposure experiment was employed and the enantiomer fractions (EFs) in tubifex tissue were maintained approximately at 0.47 during the experiment. For the spike sediment treatment, a 14 day bioaccumulation period indicated the concentrations of (-)-(R)-metalaxyl were higher than those of (+)-(S)-metalaxyl. Therefore, the bioaccumulation of metalaxyl in worms was enantioselective for these treatments. With the presence of tubifex, higher concentrations of metalaxyl in overlying water and lower concentrations in sediment were detected than in worm-free treatments. This means that tubifex has positive functions in metalaxyl's diffusion from the sediment to overlying water and in the degradation of the sediment-associated metalaxyl.