Enantioselective degradation of metalaxyl in anaerobic activated sewage sludge.

Enantioselective degradation occurs frequently for chiral pesticides in field matrices and under laboratory conditions. Metalaxyl is a chiral compound and important fungicide. In this study, the degradation of Rac- and R-metalaxyl under anaerobic conditions was studied. The degradation processes were found to follow first-order kinetics. The degradation of the S-enantiomer (T (1/2) = 2.10 days) was much faster than the R-enantiomer (T (1/2) = 8.44 days). The half-life of the Rac-metalaxyl mixture was 4.05 days, which was higher than the S-enantiomer, but lower than the R-enantiomer. These results confirm the need for emphasizing the importance of examining the fate of the stereoisomers in an environmental system.