Quantitative tracing of uptake and transport of submicrometre plastics in crop plants using lanthanide chelates as a dual-functional tracer

The uptake pathways of nanoplastics by edible plants have recently been qualitatively investigated. There is an urgent need to accurately quantify nanoplastics accumulation in plants. Polystyrene (PS) particles with a diameter of 200 nm were doped with the europium chelate Eu-β-diketonate (PS-Eu), which was used to quantify PS-Eu particles uptake by wheat (Triticum aestivum) and lettuce (Lactuca sativa), grown hydroponically and in sandy soil using inductively coupled plasma mass spectrometry. PS-Eu particles accumulated mainly in the roots, while transport to the shoots was limited (for example, <3% for 5,000 μg PS particles per litre exposure). Visualization of PS-Eu particles in the roots and shoots was performed with time-gated luminescence through the time-resolved fluorescence of the Eu chelate. The presence of PS-Eu particles in the plant was further confirmed by scanning electron microscopy. Doping with lanthanide chelates provides a versatile strategy for elucidating the interactions between nanoplastics and plants.