Heavy metal distribution in Bulgaria using Populus nigra ‘Italica’ as a biomonitor

The distribution of 30 elements in standardized poplar leaf samples collected from 100 sampling sites in Bulgaria has been investigated. Cluster analysis, frequency histograms and comparison with literature data conclude that the major part of the investigated territory is not heavily polluted by Cd, Pb and Zn, and that their concentrations, with few exceptions, are considerably lower than in some other European countries. For the other elements extreme values have not been detected.