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Influence of CA, PE, and PET microplastics on the migration of imidacloprid in porous media: Experiments and theoretical modeling
Summary
Column experiments and molecular dynamics simulations were used to investigate how cellulose acetate, polyethylene, and PET microplastics influence the transport of the pesticide imidacloprid through porous media. MPs with higher adsorption capacity retarded imidacloprid mobility, while those with lower adsorption facilitated transport, revealing polymer-specific effects on pesticide fate in soils.
Pesticides and microplastics (MPs) commonly coexist in soil, yet the overall impact of MPs on pesticide transport remains poorly understood. This study integrates column experiments and molecular dynamics (MD) simulations to investigate the impact of three typical MPs-cellulose acetate (CA), polyethylene (PE), and polyethylene terephthalate (PET)-on the transport behavior of imidacloprid (IMI). Spearman correlation analysis identified MPs' adsorption capacity as a key factor influencing IMI mobility. CA MPs showed the highest adsorption capacity (29.6 μg g), significantly higher than PE (3.5 μg g) and PET (3.2 μg g). Adsorption kinetics followed a pseudo-second-order model for CA and PET, and a pseudo-first-order model for PE, while all isotherms conformed to the Freundlich model. The effects of MPs concentration, aging, and pH on IMI migration were also evaluated. At 5 % (w/w) CA MPs, IMI migration decreased to 55.3 %. Molecular dynamics (MD) simulations showed that the diffusion coefficient of IMI in the CA MPs-quartz sand system (0.036) was much lower than in PE (0.167) and PET (0.175) systems. Aging increased oxygen-containing functional groups on MPs, enhancing hydrogen bonding with IMI and further restricting its mobility. This study provides a theoretical foundation for understanding microplastic-pesticide interactions under realistic soil conditions, thereby supporting environmental risk assessment and pollution management.