Urban tree species are commonly used for indirect monitoring of heavy metal pollution in urban environments due to their distribution and the cost-effectiveness of the analysis methods.We aimed to determine the spatial variation of heavy metal content in tree leaves at urban, rural and industrial sites in the central provinces of Thailand and also in the city of Debrecen, Hungary. Leaf samples were collected from Mimusopselengi and Ficusreligiosa in Thailand, and Celtisoccidentalis and Tilia × europaeain Hungary.Comparing the two species from Thailand, M. elengi contained Al, Cr, Fe, Na and Pb in significantly higher concentrations than F. religiosa. Meanwhile, F. religiosa contained Ca, Cu, K, Mn and Zn in significantly higher concentrations than M. elengi. Between the two species in Hungary, C. occidentalis contained significantly more Ba, Ca and Cr, while T. europaea contained significantly more Al and Ni.The species showed varying trends in metal content at the urban, rural and industrial sites as well. Ba content was the highest at the rural sites. T. europaea samples from the industrial areas contained significantly more Al, Cr and Fe than those from the urban and rural sites. Elemental concentrations for M. elengi and F.religiosa were consistent at the different sites.Our results highlight the importance of prior assessment and selection of the most appropriate species for biomonitoring studies. Metallic elements can be specific to certain species, while native and invasive species often accumulate pollutants at different rates as well
