Effect of ZnO Nanoparticles During the Process of Phytoremediation of Soil Contaminated with As and Pb Cultivated with Sunflower (Helianthus annuus L.)

Urbanization and industrialization have caused the production of pollutants in the soil, water, and air systems, negatively influencing plants, animals, humans, and the ecosystem. Heavy metals, such as arsenic (As), lead (Pb), cobalt (Co), chromium (Cr), mercury (Hg), and nickel (Ni), affect the development of organisms. In this study, as a novel alternative, the performance of zinc oxide nanoparticles (ZnO NPs) in sunflower plant growth (Helianthus annuus L.) and the decontamination of soils with As and Pb was investigated. For this purpose, in natural soil contaminated with As (0.02 mg kg of dry soil) and Pb (0.2 mg/kg of dry soil), sunflower plants were allowed to grow in pots for 25, 35, and 45 days after emergence. Morphological parameters were measured for the plants. The stems, leaves, and roots were dried (80 °C), ground, and finally, mineral analysis was performed by plasma atomic emission spectrometry (ICP). ZnO NPs were applied to the soil at two concentrations (0.3 and 0.6 mg/kg) and the control. ZnO NPs application resulted in plant growth and root length 25 days after emergence (DAE). The interaction between ZnO NPs and metals significantly negatively affected the variable root length. The roots, stems, and leaves accumulated metals at 25 and 45 DAE. Bioconcentration (BCF) and translocation (TF) factors were higher in Zn at 45 DAE. The phytoextraction by H. annuus assisted with ZnO NPs helps remediate polluted soils, potentiating the plant's hyperaccumulation characteristics. The results of this experiment offer basic information on the interaction of ZnO NPs in the phytoremediation process of soil contaminated with heavy metals. However, it is crucial to know the potential of NPs in soils with higher concentrations of contaminants in the soil, which we consider one of the limitations of this work, using low concentrations of heavy metals. Therefore, more research is required to corroborate the effectiveness of ZnO NPs in soils contaminated with Pb and Zn during the phytoremediation process with sunflower plants.

Graphical Abstract