Bioaccumulation of heavy metals in urban tree leaves

Abstract

LEAVES of nine tree species (Pinus halepensis Mill, Pinus sylvestris L., Cupressus italica, Cupressus arizoneka Greene, Quercus robur L., Quercus ilex L., Ficus nitida L., Eucalyptus globulus Labill and Casuarina equisetifolia L.) were used to inspect accumulation of heavy metals emitted at areas with different pollution load in Baku (Azerbaijan). Concentrations of Cr, Cu, Mn, Pb, Zr, Ti, V, Bi, Cd, Ni, and Zn were determined by inductive coupled plasma (ICP-MS) and EDRF (energy dispersive X-ray fluorescence). Concerning Fe, Cd, Cu, Pb, Zn and Zr concentrations, the ICP results declared a relative increase. Unlike the rest species, the concentration of Ni in E. globulus, C. equisetifolia, F. nitida and C. italica leaf samples was higher than 10mg/kg, which is the beginning of toxic concentration. V concentration still in the normal range (0.2-1.5mg/kg). All tested tree leaves have Cr concentration within the toxic range (<5mg/kg), except P. halepensis, P. sylvestris and C. italica trees. The results showed a relatively high content of Zr in genus Quercus, ranging from 0.15 to 3.13ppm. The results of EDRF were slightly different, where higher Cu (8.07%), Zn (38.6%), I (55.12%) and Co (4.86%) characterizes the industrial site, whereas areas of high traffic dominated by elevated concentrations of Pb (9.91%), Cd (0.29%), Mo (0.17%) and Cr (59.05%). These variations enhanced the idea that these sites were influenced by different sources of pollution. The findings may be useful for future surveillance as preliminary reference values for levels of heavy metals in urban and industrial settings.