Phytoremediation potential and Bioindicator Capabilities of Nerium oleander Under Traffic-Related Heavy Metal Stress

Abstract

Rapid urbanization and increasing vehicular traffic in Lahore have contributed to elevated levels of airborne heavy metals, posing risks to both ecosystems and public health. Identifying resilient plant species that can mitigate and signal such pollution is therefore critical for sustainable urban management. This study evaluated the phytoremediation potential and bioindicator capability of the ornamental shrub Nerium oleander growing in high-traffic zones of Lahore, Pakistan. Leaf samples were collected from two major polluted sites i.e., Canal Road and Ferozepur Road and compared with control samples from less polluted areas, including the Forman Christian College University (FCCU) botanical garden and adjacent residential zones. Heavy metal concentrations, particularly chromium (Cr) and lead (Pb), were quantified using Atomic Absorption Spectroscopy (AAS). Anatomical analysis through hand-sectioning revealed significant reductions in mesophyll and vascular tissue widths in plants from polluted sites. In addition, chlorophyll a and b contents showed a marked decline under metal stress. The accumulation of Cr and Pb in leaf tissues, along with associated anatomical and physiological changes, suggests that N. oleander can serve as a potential phytoremediator and bioindicator of airborne pollutants in traffic-dense settings. These results indicate a strong association between traffic intensity and metal accumulation, though further controlled studies are needed to confirm causal relationships and long-term tolerance.