Transformation of ceria nanoparticles in cucumber plants is influenced by phosphate

Transformation is a critical factor that affects the fate and toxicity of manufactured nanoparticles (NPs) in the environment and living organisms. This paper aims to investigate the effect of phosphate on the transformation of CeO2 NPs in hydroponic plants. Cucumber seedlings were treated with 2000 mg/L CeO2 NPs in nutrient solutions with or without adding phosphate (+P or –P) for 3 weeks. Large quantities of needle-like CePO4 was found outside the epidermis in the +P group. While in the –P group, CePO4 only existed in the intercellular spaces and vacuole of root cells. X-ray absorption near edge spectroscopy (XANES) indicates that content and percentage of Ce-carboxylates in the shoots of –P group (418 mg/kg, 67.5%) were much higher than those in the +P group (30.1 mg/kg, 21%). The results suggest that phosphate might influence the transformation process of CeO2 NPs in plants and subsequently their ultimate fate in the ecosystem. [Display omitted] •We compared the transformation of CeO2 NPs in cucumber plants with and without phosphate in nutrient solutions.•Results of TEM and STXM show that CePO4 located differently in roots between +P and –P group.•The chemical species distributions of Ce in shoots were different between +P and –P group by XANES.•Phosphate significantly affected the transformation of CeO2 NPs in plants. CeO2 NPs can be partially transformed to CePO4 and Ce carboxylates in hydroponic plants. Phosphate significantly affected the transformation of CeO2 NPs and subsequent translocation of Ce species.