Low-density polyethylene enhances the disturbance of microbiome and antibiotic resistance genes transfer in soil-earthworm system induced by pyraclostrobin.

Non-antibiotic chemicals in farmlands, including microplastics (MPs) and pesticides, have the potential to influence the soil microbiome and the dissemination of antibiotic resistance genes (ARGs). Despite this, there is limited understanding of the combined effects of MPs and pesticides on microbial communities and ARGs transmission in soil ecosystems. In this study, we observed that low-density polyethylene (LDPE) microplastic enhance the accumulation of pyraclostrobin in earthworms, resulting in reduced weight and causing severe oxidative damage. Analysis of 16 S rRNA amplification revealed that exposure to pyraclostrobin and/or LDPE disrupts the microbial community structure at the phylum and genus levels, leading to reduced alpha diversity in both the soil and earthworm gut. Furthermore, co-exposure to LDPE and pyraclostrobin increased the relative abundance of ARGs in the soil and earthworm gut by 2.15 and 1.34 times, respectively, compared to exposure to pyraclostrobin alone. It correlated well with the increasing relative abundance of genera carrying ARGs. Our findings contribute novel insights into the impact of co-exposure to MPs and pesticides on soil and earthworm microbiomes, highlighting their role in promoting the transfer of ARGs. This knowledge is crucial for managing the risk associated with the dissemination of ARGs in soil ecosystems.

Effect of fertilization on the degradation and enantioselectivity of fipronil in soil.

BACKGROUND: Fertilizers and pesticides are commonly used simultaneously in agriculture. However, the effects of common fertilizers on the dissipation, enantioselectivity, and metabolites of the chiral insecticide fipronil in soil are yet to be reported. RESULT: An enantioselective method for detecting fipronil enantiomers and their metabolites in different soil matrices was developed using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that organic and compound fertilizers significantly decreased the degradation of S- and R-fipronil, whereas phosphate and microbial fertilizers slightly reduced fipronil dissipation. The half-life values for S- and R-fipronil were 43.3 and 28.9 days, 99.0 and 63.0 days, 69.3 and 43.3 days, 46.2 and 30.1 days, and 43.3 and 31.5 days, respectively, in the control and the four fertilizer treatments, respectively. The enantioselectivity of fipronil enantiomers occurred and R-fipronil exhibited preferential degradation with an enantiomeric fraction (EF) of 0.4900-0.6238 in all treatments; but the four tested fertilizers decreased enantioselectivity with EF values changed from 0.4970 to 0.6238 in the control to 0.4900-0.6171 in fertilizer treatments. Two metabolites, fipronil sulfone and sulfide, were produced, and their amounts increased with culture time in all treatments. Fertilization reduced the content of fipronil sulfide and sulfone but hardly reduced the total amount of fipronil and its metabolites. CONCLUSION: Fertilizers affect the environmental behavior of fipronil in the soil. Fertilization alters the soil bacterial community, which may be an important factor. This influence is relatively complicated and should be comprehensively considered in the environmental risk assessment of pesticides. © 2023 Society of Chemical Industry.

Effect of Cd/Cu on the toxicity and stereoselective environmental behavior of dinotefuran in earthworms Eisenia foetida.

Pesticides and heavy metals commonly coexist in soil. In this study, the influence of Cd and Cu on the toxicity of rac-dinotefuran and the enantioselective behavior of dinotefuran enantiomers in soil-earthworm microcosms were investigated. The acute toxic tests showed that S-dinotefuran has higher toxic than that of R-dinotefuran. The rac-dinotefuran and Cd has an antagonistic effect on earthworms, and the Cu and rac-dinotefuran has a synergistic effect. Earthworms maybe promoted the enantioselective behavior of dinotefuran in soil. Co-exposure to Cd or Cu inhibited the dissipation of dinotefuran enantiomers (S-dinotefuran and R-enantiomers), and slightly reduced the enantioselectivity in soil. The earthworms were found to be preferentially enriched with S-dinotefuran. However, Cd or Cu attenuated the accumulation of dinotefuran enantiomers in earthworms and decreased the enantioselectivity. The effect of Cd and Cu on the environmental behaviors of dinotefuran enantiomers were correlated positively with the dose of Cd/Cu. These results showed that Cd and Cu alter the environmental behaviors and the toxicity of dinotefuran enantiomers in soil-earthworm microcosms. Thus, the influence of coexistent heavy metals on the ecological risk assessment of chiral pesticides should be considered.