Enhanced phytoremediation of Metal(loid)s via spiked ZVI nanoparticles: An urban clean-up strategy with ornamental plants

The increasing industrialization and urbanization are also triggering environmental pollution, mostly unnoticed, in the case of soil pollution due to uncontrolled contamination by toxic elemental dispersion. The present study focused on this aspect and studied the clean-up of urban soil in a low-cost and eco-friendly way to restrict arsenic (As), lead (Pb) and mercury (Hg) contamination. Four potential ornamental plants, Catharanthus roseus (vinca), Cosmos bipinnatus (cosmos), Gomphrena globose (globosa) and Impatiens balsamina (balsamina) were used along with zero valent iron (ZVI) nanoparticles (Fe NPs) for remediation of the soil spiked with As (70 mg kg⁻¹), Pb (600 mg kg⁻¹) and Hg (15 mg kg⁻¹) in a 60 d pot experiment. All plants were divided into four groups viz. control, spiked, spiked+20 mg kg⁻¹ ZVI NP and spiked+50 mg kg⁻¹ ZVI NP. FTIR and SEM were used for ZVI NP characterization. Soil and plant analyses and elemental assessments were done using ICP-MS, XRF and SEM. Among the four plants, cosmos showed the maximum accumulation of toxic elements (41.24 ± 0.022 mg kg⁻¹ As, 139.15 ± 11.2 mg kg⁻¹ Pb and 15.57 ± 0.27 mg kg⁻¹ Hg) at 60 d. The application of ZVI NP at 20 mg kg⁻¹ dosage was found to further augment plants’ potential for metal(loid)s accumulation without negatively hampering their growth. Cosmos were observed to reduce soil As from 81.35 ± 1.34 mg kg⁻¹ to 28.16 ± 1.38 mg kg⁻¹ (65.38%), Pb from 1132.47 ± 4.66 to 516.09 ± 3.15 mg kg⁻¹ (54.42%) and Hg from 17.35 ± 0.88 to 6.65 ± 0.4 mg kg⁻¹ (61.67%) at 60 d in spiked + 20 mg kg⁻¹ ZVI NP treatment. Balsamina was the most sensitive plant and showed the least metal(loid)s accumulation. In conclusion, three of these plants are potent enough to use together for a better and enhanced removal of toxic elements from the contaminated soil with cosmos to be the best amongst these in urban areas.