From compost-amended soil to plant tissues: field quantification of environmentally relevant polystyrene nanoplastics and limited translocation in Holcus lanatus L.

Field evidence for the presence and distribution of nanoplastics (NPs) in terrestrial plants remains scarce. We provide the first in-situ detection and depth-resolved quantification of environmentally relevant polystyrene nanoplastics (eNPs-PS) in field-grown Holcus lanatus L. from chronically contaminated agricultural soils in the Loire River floodplain (France), where decades of compost amendments have introduced substantial plastic debris. Using matrix-matched Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC/MS), we detected eNPs-PS throughout the soil-plant system. Concentrations in amended topsoil were up to 28-fold higher than in the reference plot, confirming the surface horizon as the primary exposure source. Polystyrene (PS)-associated signals were detected in both belowground and aboveground plant compartments, with substantially higher concentrations measured in roots (123 μg g-1 dry weight) than in shoots (32 μg g-1 dry weight). Shoot concentrations were above the detection limit but close to the quantification threshold. The resulting root-to-shoot translocation factor (TF ≈ 0.26), interpreted as a conservative semi-quantitative estimate because shoot concentrations were below the LOQ, was consistent with limited transfer between plant compartments and a root-dominated distribution pattern under field conditions. This pattern contrasts with studies using pristine monodisperse nanobeads, which reported greater mobility, highlighting the importance of particle realism when assessing NPs behavior in terrestrial environments. Overall, our findings provide field-based evidence for the presence and distribution of environmentally derived eNPs-PS in a soil-plant system under chronic exposure conditions. The qualitative consistency between field observations and previous laboratory studies using environmentally relevant nanoplastics (eNPs) provides a useful link between controlled and field investigations, while emphasizing the importance of environmentally aged and heterogeneous particles when assessing nanoplastic behavior under realistic environmental conditions.