A field study was conducted to evaluate the efficacy of enhanced tobacco for phytoremediation of contaminated soils. The experiment was performed on an agricultural field highly contaminated (1526.2 mg/kg Zn, 1158.8 mg/kg Pb and 36.8 mg/kg Cd) by the Non-Ferrous-Metal Works near Plovdiv, Bulgaria. The content of heavy metals in different parts of three varieties of enhanced tobacco (roots, stalks, lower, middle and upper leaves) was determined by ICP. A clearly distinguished species peculiarity existed in the accumulation of heavy metals in the organs of tobacco. Cd levels occur in the order, lower leaves > middle leaves > upper leaves > stalk > root, while Pb and Zn levels occur in the order middle leaves > lower leaves > upper leaves > stalk > root. The content of Cd in upper, middle, and lower leaves reached to 155.6 mg/kg, 120.8 mg/kg, 67.7 mg.kg, respectively. Pb content reached to 1062.5 mg/kg, 927.8 mg/kg, 884.4 mg/kg and Zn to 936.7 mg/kg, 860.1 mg/kg, 459.4 mg/kg. To be able to give an answer for the abilities of the enhanced tobacco to extract heavy metals from the soil and to assess the potential of enhanced tobacco for phytoextraction, the translocation factor (TF=Cshoots/Croots) and bioaccumulation factor (BF=Cshoots/Csoils) were calculated. The translocation factor for all metals is greater than 1(TF Pb -13, TF Zn -9, TF Cd -8). The BF values were lower than TF and reached to 1.2 for Pb, 3.3 for Zn and 4.9 for Cd. Higher root to shoot translocation of these metals indicated that enhanced tobacco have vital characteristics to be used for phytoextraction of these metals.None of these varieties of enhanced tobacco was specified as a hyperaccumulator; nevertheless, all varieties show potential for phytoextraction of Pb, Zn, and Cd. Further studies are required to determine the utilization of residual products of phytoextraction and to enhance the economic value of this crop when growing on industrially polluted soils.

Acknowledgements: The authors gratefully acknowledge the financial support by the Bulgarian National Science Fund (Project DFNI DH04/8).