Assessment of Particulate Matter, Heavy Metals, and Carbon Deposition Capacities of Urban Tree Species in Tehran, Iran

Air pollution is a pressing environmental concern in urban areas, with particulate matter (PM) posing serious health and environmental threats. Urban greening has emerged as a potential solution to capture and retain PM. This study assesses the PM deposition capacity of five common tree species: Morus alba (M. alba), Ailanthus altissima (A. altissima), Platanus orientalis (P. orientalis), Robinia pseudoacacia (R. pseudoacacia), and Ulmus minor (U. minor) in two highly polluted sites in Tehran, Iran. Additionally, this study investigates the accumulation of heavy metals (Ni, Fe, Cd, and Pb), Organic Carbon (OC), Elemental Carbon (EC), and Total Carbon (TC) on the leaves of these tree species. The results demonstrate species-specific differences in PM deposition capacity, with U. minor and M. alba showing high PM retention. A. altissima exhibits strong capability in adsorbing PM 0.1-2.5, while U. minor demonstrates greater retention of PM > 2.5. Moreover, the deposition of heavy metals varies among species, with R. pseudoacacia and A. altissima capturing higher levels. This study highlights the significance of appropriate tree utilization in urban environments against air pollution in order to make the air healthier in major cities. Awareness of the different tree species capacities leads urban planners and policymakers to make intelligent decisions about urban greening initiatives to improve air quality and overall well-being.