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Size-dependent stability of pesticides adsorption on nanoplastics: Microsecond atomistic-scale molecular dynamics simulations
Summary
As plastic breaks down into ever-smaller nanoplastic particles, computer simulations show that the tiniest fragments actually hold onto attached pesticides less tightly—meaning some pesticides may detach more easily from very small nanoplastics than from larger ones. This matters because it suggests that as plastic waste degrades further in the environment, it could release absorbed pesticides back out, potentially affecting how these chemicals travel through soil, water, and eventually into our food and bodies.
Microsecond atomistic-scale molecular dynamics simulations were performed to compare the size-dependent adsorption stability of different pesticides on nanoplastic (NP) particles. Spherical particles of atactic polystyrene with diameters of 1.7-5.0 nm, representing NP particles in the final stage of polymer waste degradation, were considered. The results showed stable adsorption at 5 nm NP particle, while the desorption frequency of the least stable 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid (DCVA) pollutant increases exponentially with decreasing nanoparticle diameter as indicate 1 μs simulations. The binding energy of pesticides to the smallest considered NP particle increases as cypermethrin < PCB-169 < DDT < alpha-cyano-3-phenoxybenzyl alcohol (PBA) < DCVA, with only one desorption event observed for cypermethrin. For the 5.0 nm NP particle, however, this order changed, and no desorption occurred during 1 μs simulations, even for the least stable molecules (PBA and DCVA). This underscores the key role of NP size during microplastic degradation in the stability of pollutant adsorption.