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Neonicotinoids have recently been banned in the European Union due to concerns about their environmental safety. Thiacloprid is a neonicotinoid, and is frequently used in agricultural pest control. However, the lack of quantitative methods for assessing its multiple metabolites has made it difficult to perform a comprehensive safety assessment. Therefore, we established an analytical method for effectively determining thiacloprid and its five metabolites in vegetables and flowers using QuEChERS-HPLC-MS/MS. The samples were extracted with acidified acetonitrile (containing 0.5% acetic acid) and were cleaned with graphitised carbon black (GCB) and octadecylsilane (C18) before the residue analysis. This method provided linearity ranging from 2–2000 μg kg−1, and its linear regression coefficients exceeded 0.995. Limits of Quantitation (LOQs) are achieved at 2 μg kg−1， and Limits of Detection (LODs) ranged from 0.09–0.80 μg kg−1. The method was validated on seven matrices spiked at 2, 200, and 2000 μg kg−1. Average recoveries ranged from 77–119%, with an intra-day Relative Standard Deviation (RSDr) of 1.5–13.4% and an inter-day Relative Standard Deviation (RSDR) of 0.9–14.4%. This method was used on cucumbers sprayed with thiacloprid and 19 types of flower samples collected from the field, after which thiacloprid and several of its metabolites were detected.

Agricultural soils and microplastics (MPs) are hotspots for antibiotic resistance genes (ARGs). Plastic mulch is the most important source of MPs in agricultural soil. ARGs, mobile genetic elements (MGEs), and their host profiles in long-term mulch MP-exposed soils remain unclear. In the present study, metagenomics was used to investigate the distribution patterns of ARGs and MGEs in eight Chinese provinces with a long history of plastic mulch use. A total of 204 subtypes of ARGs and thousands of MGEs (14 integrons, 28 insertions, and 2993 plasmids) were identified. A similar diversity of ARGs was found among MPs film-contaminated sites. The types of ARGs with a high abundance were more concentrated, and multidrug resistance genes were the dominant ARGs. Soils from regions with a longer history of plastic film use (such as Xinjiang province) had a higher abundance of ARGs and MGEs. The distribution of ARGs and MGEs exhibited a modular network distribution pattern. A total of 27 ARG subtypes and 29 MGEs showed co-occurrence network relationships. More than 10 common hosts of ARGs and MGEs, such as Pseudomonas, were found, and their abundances were highest in three provinces, including Xinjiang. This study may help elucidate the impact mechanism of long-term MP residues on the occurrence and spread of ARGs in soil.

As microplastics became the focus of global attention, the hazards of plastic plasticizers (PAEs) have gradually attracted people's attention. Agricultural soil is one of its hardest hit areas. However, current research of its impact on soil ecology only stops at the microorganism itself, and there is still lack of conclusion on the impact of soil metabolism. To this end, three most common PAEs (Dimethyl phthalate: DMP, Dibutyl phthalate: DBP and Bis (2-ethylhexyl) phthalate: DEHP) were selected and based on high-throughput sequencing and metabolomics platforms, the influence of PAEs residues on soil metabolic functions were revealed for the first time. PAEs did not significantly changed the alpha diversity of soil bacteria in the short term, but changed their community structure and interfered with the complexity of community symbiosis network. Metabolomics indicated that exposure to DBP can significantly change the soil metabolite profile. A total of 172 differential metabolites were found, of which 100 were up-regulated and 72 were down-regulated. DBP treatment interfered with 43 metabolic pathways including basic metabolic processes. In particular, it interfered with the metabolism of residual steroids and promoted the metabolism of various plasticizers. In addition, through differential labeling and collinear analysis, some bacteria with the degradation potential of PAEs, such as Gordonia, were excavated.

Plastic pollution in the soil ecosystem is currently receiving worldwide attention. However, little is known whether the presence of microplastics (MPs) in soil will affect the environmental behavior of pesticide residues in soil. Here, the effect of the addition of new mulch MPs (New-MPs), aged mulch MPs (Aged-MPs) and biodegradable mulch MPs (BioD-MPs) on the adsorption and degradation behaviors of two pesticides (imidacloprid and flumioxazin) in soil was investigated. Three MPs slowed down rapid adsorption stage of pesticides in soil and delayed the time to reach adsorption equilibrium. Adsorption rates: Soil Soil + New-MPs Soil + Aged-MPs Soil + BioD-MPs. Three MPs enhanced the adsorption strength of the soil system for the two pesticides, and the aging treatment of the MPs enhanced this effect. Three MPs affected the degradation process of the two pesticides. New-MPs promoted the degradation of two pesticides imidacloprid and flumioxazin, and the degradation half-lives were shortened to 0.93 and 0.85 times, respectively; while Aged-Mps and BioD-MPs delayed the degradation process of two pesticides, and the degradation half-lives were extended to 1.64 times and 1.21 times, respectively. The effect was more significant with the increase of MPs and pesticides concentration. Pesticide polarity, surface structure and functional groups of MPs are potentially important reasons for the differences in adsorption and degradation of MPs-soil systems. Our findings provide a deep insight into understanding the mechanism of interaction between MPs and pesticide residues in soil environment.

Spodoptera exigua is a worldwide pest afflicting edible vegetables and has developed varying levels of resistance to insecticides. Methoxyfenozide (MET), an ecdysteroid agonist, is effective against lepidopteran pests such as S. exigua. However, the mechanism of MET to S. exigua remains unclear. In this study, we analyzed the expression patterns of genes related to the ecdysone signaling pathway in transcriptome data treated with sublethal doses of MET and analyzed how expression levels of key genes affect the toxicity of MET on S. exigua. Our results demonstrated that 2639 genes were up-regulated and 2512 genes were down-regulated in S. exigua treated with LC30 of MET. Of these, 15 genes were involved in the ecdysone signaling pathway. qPCR results demonstrated that ecdysone receptor A (EcRA) expression levels significantly increased in S. exigua when treated with different doses of MET, and that the RNAi-mediated silencing of EcRA significantly increased mortality to 55.43% at 72 h when L3 S. exigua larvae were exposed to MET at the LC30 dose. Additionally, knocking down EcRA suppressed the most genes expressed in the ecdysone signaling pathway. The combination of MET and dsEcRA affected the expression of E74 and enhanced the expression of TREA. These results demonstrate that the adverse effects of sublethal MET disturb the ecdysone signaling pathway in S. exigua, and EcRA is closely related to MET toxic effect. This study increases our collective understanding of the mechanisms of MET in insect pests.