The global application of neonicotinoids (NEOs) has precipitated pervasive contamination of agricultural matrices, with China’s staple crop lands representing critical exposure hotspots. The occurrence and ecological risks of ten NEOs in the field soils of three major crops (i.e., rice, wheat and corn) in China were investigated in the present study. Employing an optimized UPLC-MS/MS method (LOQ = 0.01–1.7 ng/g, RSD < 12.21%), ten NEOs across 69 representative field soils (rice: 23, corn: 18, wheat: 28) were quantified. It was found that the detection frequency (DF) of the NEOs was 100% in the soil. The DFs of NEOs in the soil followed the rule: imidacloprid (IMI, 100%) > thiamethoxam (TMX, 88.4%) > clothianidin (CLO, 87.0%) > acetamiprid (ACE, 46.4%) > dinotefuran (DIN, 7.2%) > nitenpyram (NIT, 1.4%). Mean total detected NEOs concentrations exhibited crop-dependent type: wheat (1.77–214.55 ng/g) > corn (0.79–97.53 ng/g) > rice (0.75–72.97 ng/g). The IMI, CLO and TMX triad constituted over 90% of the total contribution of detected NEOs. In addition, CLO and TMX in the rice soils, IMI, CLO and TMX in the corn soils and IMI, CLO and TMX in the wheat soils had medium ecological risks. Therefore, it is particularly important for agricultural ecological protection to strengthen monitoring and take effective measures to protect agricultural ecology.

This study addresses the absence of maximum residue limits (MRLs) for tebuconazole and trifloxystrobin in edible rose petals in China by systematically evaluating the residue behavior and dietary exposure risks of these fungicides. An analytical method based on QuEChERS sample preparation coupled with UPLC–MS/MS was developed for the simultaneous determination of tebuconazole, trifloxystrobin, and its metabolite CGA321113 in fresh and dried rose petals. Field trials under the highest application conditions (184 g a.i./hm², applied twice) were conducted to investigate residue dissipation dynamics, storage stability, processing concentration effects, and transfer behavior during brewing. Results indicated that the target compounds remained stable in rose petals for 12 months at –20 °C ± 2 °C. The drying process significantly concentrated residues due to the hydrophobic nature of the compounds, with enrichment factors ranging from 3.0 to 3.9. Brewing tests further confirmed low transfer rates of tebuconazole, trifloxystrobin, and CGA321113 into the infusion, consistent with their low water solubility and high log K_ow values. Residue dissipation followed first-order kinetics, with half-lives of 1.9–2.9 days for tebuconazole and 1.2–2.7 days for trifloxystrobin. Dietary risk assessment showed an acceptable risk for trifloxystrobin (RQ = 22.7%) but a high risk for tebuconazole (RQ = 175.1%). It is recommended to set the MRL for both tebuconazole and trifloxystrobin in edible roses at 15.0 mg/kg. This standard ensures consumer safety while accommodating agricultural needs and aligns with international regulations. For the high-risk pesticide tebuconazole, measures such as optimizing application strategies and promoting integrated management should be implemented to mitigate residue risks.

This study developed a UHPLC-MS/MS method combined with a modified QuEChERS pretreatment technique to simultaneously determine diflufenican, pyroxasulfone, and their metabolites (M-1, M-3, M-25) in wheat grain and straw. The method exhibited good linearity within the concentration range of 0.0001–0.1 mg/L (r > 0.996), with a limit of quantification of 0.002 mg/kg. At three spiked levels, the average recoveries of the target analytes ranged from 82.0% to 110.1%, with relative standard deviations ≤ 13.9%. All analytes remained stable in both grain and straw matrices when stored at ≤−18 °C for 12 months. Field trials demonstrated that diflufenican residues in grains were all below 0.002 mg/kg, while residues in straw ranged from 0.002 to 0.018 mg/kg. The total residues of pyroxasulfone and its metabolites in grains ranged from 0.010 to 0.019 mg/kg, and in straw from 0.026 to 0.357 mg/kg. Dietary risk assessment results showed that the risk quotients for diflufenican and pyroxasulfone were 0.10% and 0.27%, respectively, both far below the 100% safety threshold. Based on the residue data and risk assessment results, it is recommended that the maximum residue limits for pyroxasulfone in wheat in China be set at 0.03 mg/kg for grains and 0.6 mg/kg for straw. These proposed values align with international standards while also accommodating the practical needs of domestic agricultural production and regulatory oversight.

Fluopyram is a widely used nematicide with a growing number of varieties registered both domestically and overseas. However, its absorption, transportation, and metabolism behaviors in plants have not been fully elucidated, thus hindering comprehensive assessment of the risks associated with its use. This study investigated the plant uptake, distribution, and metabolic behavior of fluopyram through 168 h hydroponic experiments. Fluopyram was easily absorbed by the roots of the tested crops, and almost 90.5% and 70.9% of fluopyram was transformed in cucumber and tomato, respectively, leading to the tentative identification of 16 metabolites using Quadrupole Time-of-Flight mass spectrometry. The metabolic reactions involved were hydroxylation, hydroxylation–dechlorination, dehydrogenation, dechlorination, and glucuronidation conjugation. Most metabolites were detected in leaves, suggesting that they have considerable potential to accumulate in the upper parts, even the edible parts. Model prediction indicated that fluopyram and high-toxicity metabolites (M430A, M412C) pose significant risks to aquatic ecosystems across trophic levels, while M574A and M574B showed reduced toxicity due to glucuronidation conjugation. These findings deepen our understanding of the behavioral characteristics of fluopyram within plants, and serve as an important reference for comprehensively assessing its risks.

Corn is a critically important agricultural crop, with different parts consumed at specific growth stages—notably, fresh corn and corn grain. The field residue behaviors of clothianidin and phoxim in fresh corn and corn grain were investigated by using a QuEChERS technique combined with UPLC-MS/MS, and the dietary exposure risks of the insecticides were evaluated. Field trials were conducted under the recommended application conditions (2250 g active ingredient per hectare of 2% clothianidin and phoxim granules, applied once) at 12 agricultural regions across China under various climatic conditions to study the residue levels of pesticides. The samples were collected at harvest of fresh corn and corn grain, separately. The results indicated that the residues of the phoxim remained stable in all samples stored at −20 °C for 6 months (180 days). At harvest, the concentrations of clothianidin in fresh corn ranged from <0.01 to 0.027 mg/kg (below the MRL of 0.1 mg/kg established by Japan); the concentrations of phoxim in fresh corn were all below 0.01 mg/kg (below the Chinese MRL of 0.1 mg/kg). In corn grain, clothianidin residues ranged from <0.01 to 0.018 mg/kg (below the Chinese MRL of 0.02 mg/kg), while phoxim residues were below 0.01 mg/kg (below the Chinese MRL of 0.1 mg/kg). Dietary risk assessment based on Chinese pesticide registration status and the per capita dietary structure of Chinese residents showed that the national estimated daily intake (NEDI) of clothianidin for the general population was 0.49 mg, accounting for 7.8% of the adult acceptable daily intake (ADI), while NEDI of phoxim for the general population was 0.048 mg, accounting for 19.2% of adult ADI. The results suggest that the associated health risks are acceptable for the general population. On the basis of these findings, it is recommended to establish an MRL for clothianidin in fresh corn in China at 0.1 mg/kg. This study provided basic data on the use and safety of clothianidin and phoxim in fresh corn and corn grain to help the Chinese government formulate a maximum residue level for clothianidin in fresh corn.