Assessment of resistance and biochemical responses of tree species as a biomonitor of heavy metals pollution in an urban-industrial setting (Yasouj, Iran)

Air pollution, particularly from heavy metals, poses significant health and socioeconomic risks in areas of high human activity. Plants offer a potential solution for air pollution remediation and can serve as biomonitors for heavy metal concentration in regions with extensive anthropogenic activities. This research investigates the uptake and accumulation of heavy metals in tree leaves, identifies tolerant tree species for planting in sensitive areas, and evaluates biochemical markers in the leaves of seven tree species collected from six urban-industrial areas with varying pollution levels in Yasouj city, Iran. The highest mean concentrations of Ni and Cu in Ulmus umbraculifera (12.57 ± 4.96 and 13.95 ± 1.99 mg/kg) and Cd, Zn, Pb, and Cr were observed in Robinia pseudoacacia (1.86 ± 0.61), Salix alba (31.32 ± 14.29), Morus nigra (5.71 ± 3.81), and Platanus orientalis (45.06 ± 7.56) mg/kg leaves, respectively. The highest metal accumulation index and comprehensive bio-concentration index were detected in Morus nigra and Ailanthus altissima, respectively. Based on air pollution tolerance index values, Platanus orientalis, Morus nigra, and Ailanthus altissima demonstrated the highest tolerance to air pollution, while Salix alba, Ulmus umbraculifera, Fraxinus excelsior, and Robinia pseudoacacia were identified as sensitive species. The results showed trees at polluted sites exhibited higher levels of malondialdehyde and anthocyanin compared to those at unpolluted areas. The study concludes that tree plantings at various polluted sites show notable variations in heavy metal accumulation and biochemical responses to pollutants, particularly heavy metals, when compared to those from the reference site.