Mass-based trophic transfer of polystyrene nanoplastics in the lettuce-snail food chain

To investigate the potential transfer of nanoplastics (NPs) from water to plants and subsequently to a higher trophic level, we established a food chain and evaluated the trophic transfer of polystyrene (PS) NPs based on mass concentrations by pyrolysis gas chromatography–mass spectrometry. Lettuce plants were cultivated in Hoagland solution with varying concentrations of PS-NPs (0.1, 1, 10, 100 and 1000 mg/L) for a period of 60 d and then a total of 7 g lettuce shoot was fed to snails for 27 d. Shoot biomass exposed at 1000 mg/L PS-NPs was reduced by 36.1 %. No significant change in root biomass was observed, however, root volume was reduced by 25.6 % at 100 mg/L. Moreover, PS-NPs were detected in both lettuce roots and shoots across all concentrations. Additionally, PS-NPs were transferred to snails and primarily found in feces (>75 %). Only 28 ng/g of PS-NPs were detected in the soft tissue of snails indirectly exposed at 1000 mg/L. Although PS-NPs were bio-diluted when transferred to species at higher trophic levels, they significantly inhibited the growth of snails, indicating that their potential risk to high trophic levels cannot be ignored. This study provides key information on trophic transfer and patterns of PS-NPs in food chains and helps to evaluate risk of NPs in terrestrial ecosystem.