Climate change, intensive agriculture, and population growth are putting immense pressure on global water resources, leading to water scarcity. One promising solution in agriculture is the reuse of treated wastewater for irrigation, although the potential health risks of residual contaminants such as nanoplastics (NPs) remain unclear. Due to their small size and ability to adsorb contaminants, NPs can penetrate biological membranes and enhance contaminant mobility and bioavailability. Limited quantitative data on the uptake and translocation of NPs in edible plants make the assessments of their impact on the food chain challenging.

This study investigates the uptake and translocation of 200 nm polystyrene NPs doped with europium (PS-Eu NPs) in hydroponically grown tomato plants. The plants were cultivated for five weeks in a Hoagland nutrient solution spiked with 1 mg/L of PS-Eu NPs. The plants were harvested and roots, stems, leaves, and fruits were collected separately, dried, and homogenized. The total concentration of Eu, determined by ICP-MS in acid-digested samples, was used as a proxy for the concentration of PS NPs, based on the known mass percentage of Eu in each PS particle. To avoid false positive results due to the potential leaching of dissolved Eu from the PS-Eu NPs, their stability in nutrient solution and plant cell environment media was evaluated by simulating the conditions during exposure. Additionally, individual PS-Eu NPs particles were measured by monitoring the Eu signal using single particle (sp) ICP-MS. PS-Eu NPs were extracted from tomato samples by enzymatic treatment, which was optimized for each plant part by adjusting the enzyme concentration and treatment time.

ICP-MS analysis of acid-digested samples showed that PS-Eu NPs were present in all plant parts, with the highest concentrations found in the roots and the lowest in the fruits. spICP-MS measurements of enzymatically extracted samples also detected individual Eu-containing NPs in all plant parts. This approach provided valuable insights into the size distribution as well as the number and mass concentration of PS-Eu NPs in tomatoes, reflecting similar trends to those observed by total ICP-MS analysis. In addition, the presence of PS-Eu NPs inside the roots was confirmed by electron microscopy.