Impact of EDTA, Citric Acid and Humic Acid on Phytoremedation of Metal Contaminated Soil by Indian Mustard (Brassica juncea)

Abstract

A pot experiment was conducted during winter season of (2013/2014) at Sakha Agricultural Research Station, Kafr El-Sheikh Governorate. The experiment aimed to investigate the effect of disodium ethylenediaminetetraacetic acid (EDTA) (0.0, 1.5, 3.0 and 4.5 mmol kg-1 soil), citric acid (CA) (0, 3, 6 and 9 mmol kg-1 soil) and humic acid (HA) (0.0, 0.2, 0.4 and 0.6 g kg-1 soil) on the phytoextraction of Cu, Zn and Pb from Al-Gabal Al-Asfar contaminated soil using indian mustard (Brassica juncea) and the leaching behavior of these metals from soil. The obtained results can be summarised in the following:- EDTA severely reduced indian mustard dry weight and visual symptoms of toxicity were observed, especially at 4.5 mmol EDTA kg-1 soil. Whilst, application of CA and HA ameliorated indian mustard growth.- EDTA was found to be the most efficient chelator in increasing concentrations of Cu and Zn in different indian mustard plant parts.- Increasing EDTA application rate up to 4.5 mmol kg-1 soil increased the concentrations of Cu by 1.91, 2.88, 3.04 and 1.56 folds and Zn by 1.43, 1.91, 1.83and 1.11 folds for roots, stem, leaves and seeds, respectively, compared to control treatment (0.0 mmol EDTA kg-1 soil).- Application of CA also increased Cu and Zn concentrations by different indian mustard plant parts, especially at 9 mmol kg-1 soil, but its efficacy was less than EDTA.- HA application increased Zn concentrations in different indian mustard plant parts with increasing its addition up to 0.6 g kg-1 soil, but its efficacy was less than that of EDTA and CA.- HA application did not affect Cu concentrations in indian mustard.- There were neither any perceptible concentrations of Pb in different plant parts of indian mustard except for roots clarifying that phytoextraction of Pb failed even after application of tested chelators. - Application of EDTA and CA to the soil increased the leaching of Cu, Zn and Pb under indian mustard cultivation with increasing application rate up to 4.5 and 9 mmol kg-1 soil, respectively. However, the effect of EDTA was many times higher than that of CA. Whilst, HA application did not affect the leaching of studied metals.- Using CA for the phytoremediation of Cu and CA and HA for the phytoremediation of Zn is favorable than EDTA despite the high efficiency of EDTA, due to the harmful effects of EDTA on plant growth and the increased risk of groundwater contamination via metal leaching.