Effect of EDTA and DTPA on Phytoremediation of Pb-Zn Contaminated Soils by Eucalyptus camaldulensis Dehnh and Effect on Treatment Time

In this research a pot experiment was carried out to investigate the remediation ability of E. camaldulensis Dehnh in Lead-Zinc (Pb-Zn) contaminated soil. The study also investigated the effects of ethylenediaminetetraacetic acid (EDTA) and diethylenetrinitrilopentaacetic acid (DTPA) on the phytoremediation efficiency of the plant species, and harvest time as a suitable dose of chelating agents was considered. When the plants had grown for 30 days, the seedlings were harvested to determine the concentration of metals in plant tissues and soil. In general, Pb level decreased in the order of: shoot > soil > root, whilst Zn content decreased in the sequence shoot > root > soil. As a second step, contaminated soils were treated with EDTA (1.5, 3, 6, 9mmolkg-1) and DTPA (1.5, 3, 6, 9mmolkg-1). The results demonstrated that chelating agents enhance metal content in E. camaldulensis. The greatest bioconcentration factor in EDTA treatments (3.94) was observed in 9EDTA treatment followed by 6EDTA treatment (3.41). Similarly this was observed for 9DTPA (2.30) and 6DTPA (2.23) respectively. With respect to non-significant difference between 9EDTA and 6EDTA treatments and between 6DTPA and 9DTPA, low doses (6mmolkg-1) were used in the third step for the highest heavy metal uptake over 30, 60 and 90 days. Results reveal that the concentration of metal soil solution decreases gradually with the passage of time. The results indicate that E. camaldulensis has the potential for the phytoextraction of metal-contaminated soils but should not be used unless the biomass containing such accumulated metals is removed for disposal. Significant improvement over current chelate-assisted phytoextraction of metals may be possible but should be implemented cautiously because of the environmental risks.