Nanoplastic–lipid interactions at marine relevant interfaces: implications for atmospheric chemistry

Abstract

Nanoplastics—originating from the fragmentation of macro- and micro plastic debris or direct industrial sources—have recently been recognized as an emerging class of marine pollutants with persistent oceanic presence. These tiny colloidal particles can potentially accumulate near the ocean surface owing to their buoyant and hydrophobic nature, positioning themselves within the sea surface microlayer (SSML), a biologically active interfacial zone enriched in lipids, proteins, and polysaccharides that shapes the chemical composition of sea spray aerosols (SSAs) generated during wave breaking events. In this study, we investigated the interfacial interactions between aged (mimicking solar UV wavelengths) polystyrene nanoplastics and a marine-representative lipid, palmitic acid (a dominant fatty acid in the ocean SSML and a known SSA constituent), using a combination of surface pressure-area isotherms, Brewster angle microscopy (BAM), and infrared reflection–absorption spectroscopy (IRRAS). The results demonstrate that nanoplastics dispersed in a seawater-proxy subphase solution significantly disrupts the structural integrity and morphology of palmitic acid films by altering intermolecular cohesion. Additionally, spectroscopic evidence suggests that these disruptions are predominantly mediated by cation–driven interactions at the carboxylate headgroup region, while the lipid hydrophobic core conserves its packing orientation. Such findings indicate that nanoplastics incorporated into SSAs can modify the surface organic film morphology during their atmospheric flight time, potentially altering aerosol mechanical stability, hygroscopicity, and cloud condensation nuclei (CCN) activity—processes that ultimately influence aerosol–cloud interactions and climate-relevant mechanisms.