Metabolomics reveals the phytotoxicity mechanisms of foliar spinach exposed to bulk and nano sizes of PbCO 3

PbCO is an ancient raw material for Pb minerals and continues to pose potential risks to the environment and human health through mining and industrial processes. However, the specific effects of unintentional PbCO discharge on edible plants remain poorly understood. This study unravels how foliar application of PbCO induces phytotoxicity by potentially influencing leaf morphology, photosynthetic pigments, oxidative stress, and metabolic pathways related to energy regulation, cell damage, and antioxidant defense in Spinacia oleracea L. Additionally, it quantifies the resultant human health risks. Plants were foliarly exposed to PbCO nanoparticles (NPs) and bulk products (BPs), as well as Pb at 0, 5, 10, 25, 50, and 100 mg·L concentrations once a day for three weeks. The presence and localization of PbCO NPs inside the plant cells were confirmed by TEM-EDS analysis. The maximum accumulation of total Pb was recorded in the root (2947.77 mg·kg DW for ion exposure), followed by the shoot (942.50 mg·kg DW for NPs exposure). The results revealed that PbCO and Pb exposure had size- and dose-dependent inhibitory effects on spinach length, biomass, and photosynthesis attributes, inducing impacts on the antioxidase activity of CAT, membrane permeability, and nutrient elements absorption and translocation. Pb exhibited pronounced toxicity in morphology and chlorophyll; PbCO BP exposure accumulated the most lipid peroxidation products of MDA and H O ; and PbCO NPs triggered the largest cell membrane damage. Furthermore, PbCO NPs at 10 and 100 mg·L induced dose-dependent metabolic reprogramming in spinach leaves, disturbing the metabolic mechanisms related to amino acids, antioxidant defense, oxidative phosphorylation, fatty acid cycle, and the respiratory chain. The spinach showed a non-carcinogenic health risk hierarchy: Pb > PbCO NPs > PbCO BPs, with children more vulnerable than adults. These findings enhance our understanding of PbCO particle effects on food security, emphasizing the need for further research to minimize their impact on human dietary health.