Acetamiprid in Rizhao green tea: Residue dynamics, degradation pathways, and ecological risks via integrated experimental and computational approaches.

This study assesses the environmental persistence, processing effects, and toxicity mechanisms of acetamiprid in Rizhao green tea. Uniquely, we integrate season-resolved field trials, full-scale factory processing and atomistic DFT-docking analyses to deliver the first "field-to-cup" mass-balance for any neonicotinoid in tea. Field trials demonstrated concentration-dependent dissipation kinetics, with half-lives decreasing from 5.54 days (spring, RD) to 4.36 days (autumn, 3 ×RD). Seasonal variations, driven by higher autumn temperatures (18.2 °C vs. 12.5 °C) and light intensity (PAR: 1451 vs. 982 μmol/m²/s), significantly accelerated acetamiprid degradation. During tea processing, fixation reduced residues (PF<1), while drying caused significant accumulation (PF 2.63-2.99) due to high vapor pressure. GC-MS identified six degradation products, two of which-6-chloronicotinaldehyde and methyl 6-chloronicotinate-showed chronic toxicity to aquatic organisms (EC₅₀: 45.2-62.7 mg/L), though acute toxicity was absent. Density functional theory (DFT) revealed reactive sites in acetamiprid's side chain, aligning with hydrolysis/oxidation pathways. Molecular docking and dynamics simulations elucidated acetamiprid's neurotoxic mechanism: stable binding to nAChRs via hydrogen bonds with Trp-86 (-12.5 ± 0.8 kcal/mol contribution) and Lys-10, yielding a spontaneous binding energy of -5.5 kcal/mol. Seasonal harvesting adjustments (prolonged spring intervals) and optimized drying protocols are proposed to minimize residues. The study underscores the ecological risks of acetamiprid's environmental persistence (soil half-life: 6.3-9.5 days) and transformation products, advocating for integrated agronomic practices to safeguard tea quality and aquatic ecosystems.