Abstract:
Pb solubility in soil and availability for plant uptake is limited due to its complexation with organic matter, sorption on oxides and clays, and precipitation as hydroxide, carbonates and phosphates (Bride, 1994). Furthermore, increased leaching of Pb during EDTA-assisted phytoextraction hasmainly been attributed to the solubility of the Pb–EDTA complexes. It is further favored by the low sorption of Pb–EDTA complexes on soil particles (Benyahya and Garnier, 1999; Chen et al., 2003; Wu et al., 2003a) compared to free ions. Release of soil-bound Pb could increase with an increase in EDTA concentration. Therefore, high levels of soluble Pb in soil solution resulting from application of EDTA may lead to contamination of ground water .The adverse effects of EDTA are not only related to the enhanced solubility of the metals but also to their low biodegradability. EDTA therefore remains in soil for extended periods of time after treatment (Thomas et al., 1998; Nörtemann, 1999; Bucheli-Witschel and Egli, 2001; Meers et al., 2005b).Due to its limited lead bioavailability, an approach to increase its bioavailability is essential to the success of phytoremediation. Hence the potential of natural chelator: garlic extract was investigated. Therefore, Chelate – enhanced phytoextraction was performed using Helianthus annus, Brassica juncea, spinacea oleracea and Amaranthus. virids by applying the chelators (EDTA and garlic extract) as solution to the soil about 1 week before harvesting.
