Effect of nano cerium oxide on soybean (Glycine max L. Merrill) crop exposed to environmentally relevant concentrations

This study evaluated the uptake and translocation of cerium nanoparticles (CeO₂ NPs) and soluble Ce(NO₃)₃ by soybean plants (Glycine max L. Merrill) under the whole plant life-cycle and relevant environmental concentrations, 0.062 and 0.933 mg kg^-1, which represent maximal values for 2017 in agricultural soils and sludge treated soils, respectively. The experiments were carried out using a nutrient solution. Cerium was detected in the soybean roots epidermis and cortex, leaves, and grains, but it neither impaired plant development nor grain yield. The concentration of Ce in the shoot increased as a function of time for plants treated with Ce(NO₃)₃, while it remained constant for plants treated with CeO₂ NPs. It means that CeO₂ NPs were absorbed in the same rate as biomass production, which suggests that they are taken up and transported by water mass flow. Single-particle inductively coupled plasma mass spectrometry revealed clusters of CeO₂ NPs in leaves of plants treated with 25 nm CeO₂ NPs (ca. 30-45 nm). The reprecipitation of soluble cerium from Ce(NO₃)₃ within the plant was not confirmed. Finally, bioconcentration factors above one were found for the lowest concentrated treatments. Since soybean is a widespread source of protein for animals, we draw attention to the importance of evaluating the effects of Ce entrance in the food chain and its possible biomagnification.