A novel sustainable phytoremediation approach using green-synthesised iron oxide nanoparticles to enhance multi-metal removal by Chrysopogon zizanioides, Cynodon dactylon, and Cymbopogon citratus in contaminated soil

Rapid industrialization and urbanization have led to the rise in the levels of heavy metals in soil necessitating the need for remediation measures. Conventional remediation techniques are often costly, energy-intensive, and disruptive to soil structure limiting their environmental sustainability. The current study investigates a novel phytoremediation approach using Chrysopogon zizaniodes, Cynodon dactylon, and Cymbopogon citratus enhanced by synergistically applied, green-synthesised α-Fe 2 O 3 nanoparticles to amplify heavy metal remediation. The pot experiment focused on the soil collected from the industrial area of Barotiwala, Himachal Pradesh, India, contaminated with heavy metal(oid)s (zinc, arsenic, lead, nickel, chromium) for a time period of 6 months. The green-synthesised α-Fe 2 O 3 nanoparticles, prepared from Mangifera indica leaves, were added in soil at 3 concentrations (10, 25, and 50 mg kg −1 ) to assess their effect on plant stress and metal remediation efficiency. Plants grown in α-Fe 2 O 3 nanoparticles amended soil exhibited markedly reduced oxidative stress, as evidenced by significantly lower levels of proline, malondialdehyde, and H 2 O 2 content especially in vetiver grass at 25 mg kg −1 (0.050), (0.337) for proline and H 2 O 2 respectively. The stress regulatory enzymes (guaiacol peroxidase (GPX), catalase (CAT), and ascorbate peroxidase (APX)) also showed significantly better results in the plants grown in the soil with nanoparticles indicating enhanced ROS detoxification and improved physiological resilience. The result was significantly better for GPX at 25 mg kg −1 for lemon grass (3.007), for CAT at 25 mg kg −1 and 50 mg kg −1 for vetiver grass (0.590) (0.613), and for APX at 50 mg kg −1 in vetiver grass (2.770). Further, phytoremediation potential of the grasses was measured using translocation factor and bioaccumulation factor in roots and shoots. Integration of α-Fe 2 O 3 nanoparticles in soil to improve phytoremediation substantially enhanced plant tolerance to oxidative stress and significantly improved remediation efficiency. Nanoparticle assisted phytoremediation offers a promising, and sustainable solution for the restoration of heavy-metal-contaminated soils.