Impact of plastic nanoparticle (PNP) characteristics on the mobility of oxaliplatin in saturated soil

Plastics are used extensively across multiple industries, leading to widespread environmental contamination, including the formation of microplastics and plastic nanoparticles (PNPs). Secondary PNPs, generated through environmental weathering, differ significantly from primary PNPs in their size, shape, and surface chemistry but transport experiments using secondary PNPs are scarcely reported in the literature due to analytical challenges. In this study, we examine the impact of different PNPs – focusing on five secondary PNPs representing the most abundant plastic products, landfill-derived PNPs (>20 years old) that were extracted from landfill soil, and classically-studied polystyrene nanobeads – on the transport of a representative contaminant (oxaliplatin, an essential and common anticancer drug). Using fully water-saturated soil and environmentally-relevant oxaliplatin and PNP concentrations, we evaluated how variations in PNP properties, such as size, morphology, surface charge, and density influence oxaliplatin mobility. Our results indicate that secondary PNPs affect oxaliplatin transport vastly differently compared to the polystyrene nanobeads, linking the differences to the PNP morphology, (bulk) density, size and zeta potential distributions. This work emphasizes the need to incorporate more realistic PNPs to better understand their impact on transport dynamics of contaminants in soil systems.