Influence of nanoparticles on the phytoremediation efficiency of Tagetes erecta L.

Phytoremediation is a cost-effective and environmentally sustainable approach for eliminating hazardous heavy metals from contaminated soils; however, its efficacy can be enhanced through innovative amendments. This study aimed to evaluate the impact of magnesium oxide (MgO) and zinc oxide (ZnO) nanoparticles (NPs) on the phytoremediation potential of Tagetes erecta for cadmium (Cd), copper (Cu), and lead (Pb) at soil concentrations of 100 mg/kg for each metal and 100 mg/kg for each NP, for the first time. Growth metrics, root volume, moisture content, tolerance index, and metal accumulation in both roots and shoots were also assessed. The findings indicated that T. erecta efficiently accumulated Cd (19421 mg/kg), Cu (1977 mg/kg), and Pb (508 mg/kg) in the roots (phytostabilization). Magnesium oxide and ZnO NPs reduced cadmium accumulation in both roots (29% and 32% respectively) and shoots (40% and 31% respectively), in addition to enhancing the shoot biomass of Cd stressed plants. Root Pb accumulation considerably increased with MgO NP and ZnO NP treatments (226% and 410% respectively), whereas Cu accumulation reduced with MgO NP application (9%) and enhanced with ZnO NP application (274%). Notably, plants treated with Cu + ZnO NP, Pb + MgO NP, and Pb + ZnO NP showed higher accumulation of their respective metals than metal-only treatments, indicating enhanced phytostabilization potential. These results designate MgO and ZnO NPs as efficacious amendments for enhancing Pb phytostabilization, and ZnO NPs for increasing Cu phytostabilization in T. erecta, while underscoring the necessity of optimising nanoparticle concentrations to reconcile metal immobilisation with plant growth. This study offers a solid foundation for enhancing phytoremediation using NPs for soils contaminated with heavy metals. However, large scale field studies have to be conducted to assess the long-term effects of NPs on the environment.