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Abstract
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Assisted phytoremediation technique is greatly progressed, but is still in development and needs further study. Thereby, in this study, Ligustrum texanum (Wax-leaf Privet) was exposed to soil treated with the various concentrations of lead nitrate (Pb(NO3)2) (0, 100, 300, 500, and 700 mg L–1) and humic acid (HA) (0 and 300 mg L–1) irrigation solution for the three-month period, in order to evaluate the species’ ability to phytoremediation of soil Pb2+; and the effect of HA on this process. Un-planted pots were also used and treated with Pb in order to investigate the direct role of plants in soil remediation. The effect of Pb and HA on various plant morphological traits (plant tissue’s fresh and dry weight, plant and root length, number of leaves, and collar diameter) were also detected. Up to 200 µg g–1 Pb in soil (as a result of 500 mg L–1 Pb irrigation solution), Pb led to a positive (stimulative) effect on various plant morphological traits, in contrast, Pb in higher concentrations had a negative (repressive) effect on plant growth. Humic acid had increased plant morphological traits whilst is not promising for contaminated soil phytoremediation process due to reducing uptake and accumulation of Pb through plant roots. According to the results, this evergreen species is prominent for Pb phytoremediation in contaminated soils due to its high tolerance to Pb contamination, high Pb uptake, and plant affordability.
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