Decontamination of soils polluted with heavy metals using plants as determined by nuclear technique

The objectives of this work were three folds. First, to study the mobility and fate of heavy metals in two polluted sites (Mostorud soil, irrigated with contaminated water for more than 30 years and El-Gabal EL-Asfar soil, subjected to sewage effluent irrigation for more than 50 years) utilizing a modified tessier's sequential extraction procedure to evaluate the effect of total metal concentrations on metal partitioning into different fractions. Second, to evaluate the efficiency of some plant species (sunflower, cotton, penakium, Napier grass, and Squash) to extract heavy metals out of polluted soils. Third, to enhance the phyto-extraction of heavy metals by sunflower plant using some chemical chelators (citric acids, EDTA, and Ammonium nitrate) in order to improve the remediation of pollutants as well as to protect soil quality.It was observed that the distribution of heavy metals in various chemical fractions depends on the total heavy metals content. The distribution of heavy metals forms in the studied soils was in the following decreasing order: residual > Fe-Mn oxides > carbonates > organic > exchangeable > water soluble.Either higher metal accumulation in shoots or enhanced metal accumulation in roots was mainly due to improved phyto-extraction or rhizo-filtration efficiency, respectively. Heavy metals accumulation in shoots and roots of the investigated plant species was as follow: sunflower > cotton > penakium > Napier grass > Squash with a lower order of magnitude. Sunflower showed superiority for heavy metals extraction.Application of chemical chelators (soil amendments) enhanced the phyto-extraction efficiency of heavy metals by sunflower in both Mostorud and El-Gabal El-Asfar soils. Citric acid enhanced metals accumulation in shoots and roots more than EDTA and ammonium nitrate. Citric acid with rate of 20 m mole/kg soil was the best chelators to enhance phyto- extraction of heavy metals by sunflower.