Biomonitoring of airborne metals using tree leaves: Protocol for biomonitor selection and spatial trend

In northwest of Iran, airborne particulate matter originated from drying Urmia Lake is threaten the health of surrounding communities due to salt particles and heavy metals. This study aimed to use leave of local trees for biomonitoring of toxic metals and to evaluate tolerance of the trees against air pollution due to greenbelt development. Leaf samples were taken from four dominant tree species including Vitis vinifera, Juglans regia, Ulmus umbraculifera and Popolus alba in two radial distances (5 and 10 km) around the Urmia Lake in 32 sampling sites. The concentration of Cd, Pb, Ni, As, Cu, Zn and Na in the leaves were extracted according to method 3050B defined by United States Environmental Protection Agency (USEPA) and analyzed by ICP-AES technique. According to the levels of air pollution tolerance index (APTI), Popolus. alba was classified as more sensitive and Vitis. vinifera as moderately tolerant. The accumulation/existence of metals in the leaves can be arranged as follows: Na > Zn > Cu > Ni > Pb > As > Cd. Our findings showed that Popolus. alba can be applied as a local biomonitor and Vitis. vinifera can be used as a good sink of air pollutants for greenbelt development around the drying Urmia Lake. • The results show that APTI is a suitable index for selection of tree species as biomonitor and green belt development. • Determination of metal concentration level in local tree leaves is suggested as a good tool for mapping of airborne metal. • The local trees can be suitable for development of greenbelt in order to improve air quality, and also for biomonitoring of air pollution.