Leaves as Global Filters: Comparative Phytomonitoring of PM, Heavy Metals, and Microplastics in 13 Countries Across 4 Continents - Dataset

Urban trees function as passive biofilters, intercepting airborne pollutants such as particulate matter (PM), trace elements (TEs), and microplastics (MPs). In this globally scaled study, we assessed pollutant retention on the foliage of tree species sampled across 13 cities in 13 countries spanning Europe, Asia, Africa, and Australia. Using standardized protocols, we quantified PM accumulation by size fraction (PM₁₀–₁₀₀, PM₂.₅–₁₀, PM₀.₂–₂.₅), measured wax-bound versus surface-bound PM, and analyzed leaf wax quantity. FTIR-ATR spectroscopy was employed to detect polymer-specific MPs, while XRF spectroscopy was used to determine internal TE concentrations.             Results revealed strong geographic gradients in PM and TE accumulation, with cities like Marrakesh and New Delhi showing the highest pollutant loads, while Tokyo and Sydney exhibited the lowest. Coniferous species such as Cupressus sempervirens and Picea pungens consistently accumulated the most PM and metals, though certain broadleaf species (e.g., Platanus × hispanica, Acer platanoides) also performed well depending on local conditions. MP particles were found on foliage in all cities, with species-specific differences in polymer diversity. Interestingly, MP retention was decoupled from PM and TE accumulation, suggesting divergent deposition pathways.             This study underscores the dual influence of plant traits and urban context on pollutant retention and highlights the utility of tree leaves as integrative samplers of atmospheric pollution. Our findings support trait-based species selection to optimize ecosystem services in urban greening and air quality mitigation strategies.