Effect of Chemical Forms of Lead, Cadmium, and Zinc in Polluted Soils on Their Uptake by Tobacco

The objective of this experiment is to investigate the chemical distribution of lead (Pb), cadmium (Cd), and zinc (Zn) in different fractions of the soils, industrially polluted by the Non-Ferrous-Metal Works near Plovdiv, Bulgaria and the effects of concentration and different chemical forms of the elements in soil on their uptake by tobacco. The results of this experiment confirmed that potential bioavailability of heavy metals is strongly controlled by their chemical forms related to solubility and exchangeable and carbonate forms are the most important form of heavy metal uptake by plants. Tobacco has an exceptional capacity to accumulate Pb, Cd, and Zn in high heavy metal exposure conditions, while under lower-heavy metal exposure condition tobacco was apparently similar to other leaf crops in heavy metal accumulation potential. The experimental data obtained for the presence of Pb, Cd, and Zn in the different parts of tobacco grown in an industrially polluted region showed that their amounts were mainly due to the heavy-metal containing aerosols falling from the atmosphere. Part of them, however, got into the soil, and from there penetrated via the root system into the tobacco plants and accumulated into their different aboveground parts.