Species-specific accumulation and bioconcentration patterns of phosphorus and heavy metals in urban tree leaves across contrasting pollution gradients in Dhaka, Bangladesh

Abstract

Urban trees play a vital role in mitigating environmental pollution, yet their responses to heavy metal stress across contrasting urban gradients remain poorly understood. This study investigates the accumulation patterns of phosphorus (P) and six heavy metals (Zn, Cu, Co, Pb, Ni, Cr) in leaves and associated soils of nine dominant tree species across control and polluted sites in Dhaka, Bangladesh. Two-way ANOVA revealed significant (p < 0.05) site effects for P, Ni, and Cr, and pronounced species-specific significant (p < 0.001) differences in Zn uptake. Leaf P concentrations generally declined under pollution, while species such as Syzygium cumini and Terminalia catappa showed elevated heavy metal content, indicating varied tolerance mechanisms. Bioconcentration factors (BCFs) highlighted differential metal accumulation capacities, with increased Pb and Ni uptake in select species under polluted conditions. Pearson correlation and PCA analyses revealed complex interactions among elements, with strong antagonistic relationships between Pb and Co/Cr, and a positive association between Pb, Ni, and Cu. PCA further distinguished control and polluted sites based on metal profiles, underscoring pollution-driven shifts in elemental composition. These findings suggest that species-specific uptake behaviors are crucial for urban ecosystem management. The study identifies resilient tree species with phytoremediation potential, offering valuable guidance for sustainable urban greening and pollution mitigation in rapidly urbanizing cities.

DOI: http://dx.doi.org/10.5281/zenodo.18011518