Abstract
Studies often neglect the different trends between enantiomers in soil chiral contaminants. In the present study, paclobutrazol was chosen as the target analyte and the selective degradation patterns of this chiral pesticide were investigated in soils. After 14 days of culture, the degradation kinetics results demonstrated the degradation process of the two enantiomers conforms to first‑order degradation kinetics equation, and the degradation rates were significantly different (paired t-test, P < 0.05). The degradation rate of (2S,3S)-paclobutrazol (S-paclobutrazol) was higher than that of (2R,3R)-paclobutrazol (R-paclobutrazol), with the concentration decrease of 42.6 and 28.7%, respectively. Meanwhile, the enantiomer fraction (EF) was 0.43 at final sampling point, and the half-life (t1/2) of S-paclobutrazol and R-paclobutrazol were 17.3 and 28.9 days,which demonstrated significant enantioselective degradation. Results from this study served to enhance our understanding about the enantioselective degradation behaviors of chiral pesticides, which provided some scientific basis for the potential risk assessment of chiral pesticides in the environment.
Highlights
The enantioselective degradation patterns between enantiomers in chiral contaminants are often overlooked and Utembe[3] have reported the importance of studies about toxicity caused by chiral contaminants, but a fraction of studies investigated the different fate when chiral compounds enter the environment, which results in an absence of information regarding their enantioselectivity
We focused on the degradation behaviors of chiral contaminants; and paclobutrazol was chosen as the model organic molecule
According to previous studies,[22,23] enantioselective degradation of triadimefon was found in soil, in addition, the stereoselective enrichment of triadimefon was observed by Scenedesmus obliquus, which resulted in stereoselective toxicity
Summary
People have paid close attention to soil contaminants to predict potential environmental problems caused by harmful substances.[1,2] In contrast, the enantioselective degradation patterns between enantiomers in chiral contaminants are often overlooked and Utembe[3] have reported the importance of studies about toxicity caused by chiral contaminants, but a fraction of studies investigated the different fate when chiral compounds enter the environment, which results in an absence of information regarding their enantioselectivity. Studying the enantioselective degradation of chiral pollutants in experiments that simulate environmental behaviors could provide a more accurate assessment of enantiomeric toxicity when chiral compounds enter in the environment. The commercial paclobutrazol forms consist of one pair of enantiomers (2S,3S; 2R,3R).[5] these two enantiomers have different activities, R-paclobutrazol has proved to be good fungicidal, and S-paclobutrazol could play an important role in regulating plant growth.[6] In addition, the chiral structure can lead to selective degradation and enantiomeric toxicities for non-target organisms when paclobutrazol is released into the surrounding environment.[7,8,9]
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