Impact of iron oxide nanoparticles on a lead-polluted water-soil-plant system under alternating periods of water stress

Iron oxide nanoparticles (IONPs) are promising materials for the remediation of trace elements, which are a significant source of soil pollution. Thus, in an attempt to improve the phytoremediation process, the addition of IONPs to soil was investigated in this study. A long-term experiment was performed in a pot to assess the potential of magnetite (Fe3O4) nanoparticles (NPsMagn) to modify lead (Pb) availability in sunflower (Helianthus annuus) and its behavior in a water-soil-plant system under repeated water-deficiency stress. The plants were grown either in control soil, Pb polluted soil (final added lead 375 mg kg-1), Pb-polluted soil containing 1% dry weight NPsMagn or Pb polluted soil containing 1% dry weight micro-sized magnetite for 90 days. The Pb-polluted soil and Pb-treated soil containing NPsMagn did not affect plant growth, whereas NPsMagn had a reduced oxidative impact given that a decrease in lipid peroxidation was observed in their presence. The magnetic susceptibility measurements and Fe content in sunflower plants and leachates suggest that NPsMagn penetrated the roots but were not dispersed in soil solution. In addition, the Pb content increased by 102% and 22% in the leaves and stems of the plants treated with NPsMagn, respectively. Based on the Pb content in soil solutions, NPsMagn decreased the Pb content in the leachate by 50%. During the water stress periods, NPsMagn significantly improved water retention in the soil and relative water content in the plants. Consequently, NPsMagn improved the Pb availability and accumulation in sunflower plants in TE-contaminated soils, which are unfavorable for plant growth. This study also highlights the favorable effects of NPsMagn on Pb stabilization in soil, reducing its loss in leachates and enhancing plant tolerance during water stress periods. Iron oxide nanoparticles (IONPs) are promising materials for the remediation of trace elements, which are a significant source of soil pollution.