Differential adsorption of dinotefuran by biodegradable PBAT and PLA microplastics and the vectoring risk to...

Biodegradable mulch microplastics (BMPs), such as PBAT and PLA, are widely used in agriculture but can persist in soils and carry coexisting pesticides like dinotefuran (DIN). Despite its widespread use, DIN's environmental fate and microbial toxicity remain insufficiently understood. This study explores the adsorption behavior of DIN on PBAT and PLA and assesses the toxicity of MPs‑neonicotinoid complexes. To provide a more comprehensive understanding, two structurally related neonicotinoids, imidacloprid (IMI) and clothianidin (CLO), were included as comparative references. Adsorption kinetics and isotherms were measured, along with multi-scale characterization (SEM, XRD, FT-IR, XPS, contact angle). The results were integrated with Escherichia coli (E.coli) inhibition assays to assess microbial toxicity. PBAT exhibited a rougher surface with lower crystallinity (7.8% vs 17.1%), and greater hydrophobicity (contact angle 107.7° vs 92.9°) compared to PLA. This increased hydrophobicity likely contributed to the higher adsorption capacity of PBAT for DIN, as confirmed by Langmuir isotherm fitting (Q_m ≈ 15.2 mg·kg^-1 for PBAT vs Q_m ≈ 4.69 mg·kg^-1 for PLA). FT-IR/XPS indicated hydrogen-bonding/dipole interactions acting cooperatively with hydrophobic association. Increasing CaCl₂ (0-0.1 mol·L^-1) enhanced adsorption while NaCl produced a biphasic response, that is low-level promotion, mid-high suppression. MPs-DIN mixtures more strongly inhibited E.coli than single exposures. These results identify BMPs as potential vectors of neonicotinoids and highlight polymer chemistry and environmental modulators in co-exposure risk assessments.