Foliar polystyrene nanoplastics modulate cadmium uptake and root-to-shoot translocation in hydroponic Spinacia oleracea L.: Time- and concentration-dependent responses

The accumulation of plastics and heavy metals (HMs) in the environment has become a significant global concern due to their persistence, ubiquity, and potential ecological impacts. Atmospheric micro- and nanoplastics (MP, NP) are capable of undergoing long-range transport and can be deposited onto plant shoots through precipitation, thereby exposing aerial plant tissues to these particulate contaminants. In this study, the effects of varying concentrations of polystyrene nanoplastics (PSNPs) (0, 10, 50, 100, 200, and 400 mg L -1 ), applied via foliar spraying, and cadmium (Cd) (0 and 5 mg L -1 ) were evaluated on the growth parameters and chemical composition of spinach ( Spinacia oleracea L. ) grown under hydroponic conditions. The experiment was carried out over three exposure durations—2, 4, and 6 weeks—designated as t 1 , t 2 , and t 3 , respectively.