The influence of oxytetracycline on the degradation and enantioselectivity of the chiral pesticide beta-cypermethrin in soil.

Pesticide residues most likely coexist with antibiotics due to the application of animal-based fertilizers in agriculture. In this study, the degradation and enantioselectivity of beta-cypermethrin in soil and chicken manure-amended soil were investigated. The effects of oxytetracycline on the soil microbial community were also estimated. The results showed that the half-life of beta-cypermethrin in the soil was 16.9 days and that the (+)-enantiomer was degraded preferentially in both pairs of enantiomers. The metabolites cis/trans-DCCA(3-(2',2'-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid) and 3-PBA (3-Phenoxybenzoic acid) were detected. The trans-DCCA concentrations ranged from 0.094 to 0.120 mg/kg, which were higher than the concentrations of cis-DCCA (0.091-0.120 mg/kg) and 3-PBA (0.022-0.061 mg/kg). In the presence of oxytetracycline, beta-cypermethrin degradation was inhibited slightly, while the enantioselectivity was not affected. Oxytetracycline increased the enrichment and persistence of the metabolites. Addition of chicken manure decreased the cis-DCCA residue levels in the soil and alleviated the effect of oxytetracycline; however, chicken manure increased the accumulation and persistence of 3-PBA. In addition, oxytetracycline perturbed the structure of the soil microbial community. The abundance of Proteobacteria increased, while the abundances of Firmicutes and Actinobacteria decreased. These changes might affect the biodegradation of beta-cypermethrin and its metabolites. Combined pollution with antibiotics should be considered for its potential impact on pesticide residues.