Calcium nanoparticle-assisted phytostabilisation of toxic metals enhances soil-dependent improvements in the nutritional and safety profile of Amaranthus hybridus.

This study investigated the efficacy of calcium nanoparticles (CaNPs) in mitigating heavy metal (HM) toxicity and enhancing the nutritional quality of Amaranthus hybridus grown in soils from the Osun riverbank (RB) and Ido-Osun dumpsite (DS). Cultivation included control treatments (RB-C, DS-C), foliar application (RB-T1, DS-T1), soil application (RB-T2, DS-T2), and combined soil-foliar application (RB-T3, DS-T3) at 75 mg L-1 CaNPs. DS soil exhibited 4.93-fold higher pollution than RB, with lead (Pb) predominant. CaNP applications significantly enhanced biomass and antioxidant activity while promoting phytostabilisation (translocation factor <1). Notably, shoot Pb concentration decreased from 11.10 to 2.202 mg kg-1 in DS following soil application, and the translocation of Fe, Cu, and Cr was effectively restricted. CaNP treatment also enhanced antioxidant activity and nutritional quality. The human health risk assessments revealed that CaNPs effectively reduced the hazard index (HI) of RB from an unsafe 1.618 to below the safety threshold (HI < 1), rendering them safe for human consumption. Despite a notable HI reduction in DS vegetables, residual Pb levels exceeded safe limits (HI >1), posing persistent non-carcinogenic health risks upon ingestion. Thus, while CaNPs effectively remediate RB soils, hyper-polluted DS environments require further optimization.