Enhancement in Phytoremediation Efficiency of Tagetus erecta with the Application of Nano-scale Zero Valent Iron (nZVI) for the Restoration of Lead Contaminated Soil: an Approach Toward Sustainability

Lead is ubiquitously distributed toxic heavy metal present in the environment without any biological function. The issue of lead pollution in soil has attracted widespread attention due to the rapid development of industrialization. The current study was designed to evaluate the effect of nanoscale zero-valent iron (nZVI) on the phytoremediation of lead. Pot experiments were conducted to assess the potential of Tagetus erecta for the removal of lead (Pb) from contaminated soil (only lead) and along with zero valent iron nanoparticle amendments (Pb + nZVI). The nZVI were synthesized by the borohydride reduction method and characterized with the help of a scanning electron microscope (SEM), X-ray diffraction (XRD), and zeta sizer. Plantlets were exposed to 250 and 500 mg/kg Pb concentrations along with nZVI amendments at various dosages (100, 300, and 500 mg/kg) for 3 months. The plant morphological, physiological, and biochemical parameters along with bioconcentration and translocation factors were also determined during the pot experiments. One-way ANOVA and Tukey multiple comparison tests were performed for the determination of statistical analysis. The root length, shoot length, and biomass significantly (P < 0.05) increased by 39%, 34%, and 45%, respectively, in the pots having 500 mg/kg Pb + 500 mg/kg nZVI treatments in comparison to Pb-only treatment (500 mg/kg). Total protein content in plant parts was also significantly inclined, while proline content reduced significantly (P < 0.05) with the addition of nZVI. Similarly, the Pb accumulated in roots and shoots was 44% and 17% higher in nZVI-amended pots (500 mg/kg Pb + 500mg/kg nZVI). The values of a bioconcentration factor greater than one revealed that Tagetes erecta is a suitable hyperaccumulator plant species for removing lead from contaminated soil. Thus, it has been concluded that the association of nZVI in the phytoremediation process overcomes Pb stress and enhanced the uptake efficiency.