Interactions between microplastics from agricultural films and soil in regulating atrazine adsorption: A mechanistic and environmental relevance study

The widespread application of agricultural films has resulted in the accumulation of microplastics (MPs) in soils, creating a coexistence with pesticides like atrazine. This study investigates the environmentally relevant interactions between field-aged polyethylene agricultural films (FAPE), virgin polyethylene (VPE), and soil in regulating atrazine adsorption. SEM-EDS and Raman analyses revealed that field aging significantly alters MP properties, introducing roughness, cracks, and oxygen-containing functional groups. Batch experiments demonstrated that the addition of MPs (1 wt%) to black soil enhances the overall adsorption capacity for atrazine, with FAPE exhibiting a higher affinity than VPE. Kinetic and isotherm modeling indicated that adsorption is a multi-step process controlled by intra-particle diffusion and surface heterogeneity. Density functional theory and interaction region indicator analyses further suggested that oxidation-induced functional groups on FAPE facilitate additional intermolecular interactions, including possible hydrogen bonding, beyond the van der Waals interactions dominating VPE. Particle size, MP dosage, and aging degree collectively influenced atrazine partitioning between soil and MPs, highlighting the importance of MP characteristics in regulating pesticide fate. These findings demonstrate that environmental aging substantially alters the adsorption behavior of agricultural-film-derived MPs and should be considered when evaluating the environmental fate and ecological risks of pesticides in agricultural soils.