Season-based phytoremediation potential of brown mustard for lead decontamination: effect of EDTA chelation and antioxidant enzyme activity

Phytoremediation technology is an environmentally benign, potent, and cost-effective approach for treating contaminated ecological sites. To yield a worthwhile remediation performance, phytoremediation technology involves amalgamating multifarious techniques and strategies. The primary objective of this research was to look into the effects of seasonal changes, contamination level, and EDTA chelation on Brown mustard's potential to extract Lead (Pb) from synthetically contaminated soil and its response to antioxidant enzyme activity. Soil samples containing 5 mg kg^-1 of EDTA were spiked with 200, 500, and 1000 mg kg^-1 of Pb, while the control group (unspiked) without EDTA addition was used. The results indicated that adding EDTA in winter (winter + EDTA) significantly increased (<i>p</i> < 0.05) plant growth by 18.83%. Observing the seasonal variation, the removal efficiency of Pb was achieved in this order: summer + EDTA > winter + EDTA > summer + No EDTA > winter + No EDTA. The results also showed that the removal rate had improved up to 52.53% as the concentration of Pb rose from 67 to 500 mg kg^-1 but showed a decline after reaching 1000 mg kg^-1, indicating a maximum Pb stress level. Additionally, the EDTA chelation during winter demonstrated a significant effect on the ability of Brown mustard to accumulate higher levels of Pb in both roots and leaves, with 500 mg kg^-1 as the optimal level taken by the plant throughout the experiment. Except for CAT, the increased enzyme activities were observed under EDTA chelation while Pb-stress (1000 mg kg^-1) reduced the enzyme activities by over 4%. The findings suggest that having 143 U/g CAT, 285 U/g SOD, and 14.9 U/g MDA in the summer season with EDTA amendments were the most suitable recourse for decontamination of Pb-polluted soil compared to a single-factor treatment.