Direct Evidence for the Carrier Effect of Nanoplastics in Plants via In Situ Mass Spectrometry Imaging

To provide the direct evidence for comigration of plastic particles and additives in organisms, for the first time, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was employed to obtain in situ imaging characterization of the migration behaviors of nanoplastics (NPs) and additives in potted cactus stems. When polystyrene nanoplastics (PS-NPs) loaded with the antioxidant tris(2,4-di- tert -butylphenyl) phosphite (AO168) and flame retardant diphenyl phosphate (DPhP) were continuously exposed directly to the pith for 7 days, the additives comigrated with PS-NPs upward along stems. On the low cross-section, concentrations of PS, AO168 and DPhP were 84.8 ± 7.3, 1.5 ± 0.1, and 7.1 ± 1.9 μg/cm 2, respectively; the corresponding values on the high cross-section were 7.4 ± 0.8, 1.4 ± 0.1 and 3.8 ± 0.2 μg/cm 2 . In contrast, AO168 and DPhP were undetectable in high cross sections of the PS-NPs-free control under identical exposure levels. The mapping degrees of additives to PS-NPs decline from 63.1% at low cross-section to 1.0% at high cross-section, indicating progressive dissociation during translocation. In vitro experiments demonstrated that PS loading can significantly reduce the degradation efficiency of additives within the cactus bleeding sap. The PS-NPs entering the stems exert a carrier effect, thereby facilitating the long-distance translocation of additives to distal plant tissues.