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

Abstract

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