Comparison of Organic Acids and Chelates for Enhancing Phytoremediation of Lead from a Contaminated Soil

Phytoremediation is a method for decreasing lead contamination in soil and the use of chelates increases the efficiency of this method. In this study, phytoremediation efficiency of savory plant (Satureja hortensis L.) to remove lead from contaminated soil was investigated in the presence of chelates including ethylene-diamine tetra-acetic acid (EDTA) and diethylene diamine penta-acetic acid (DTPA) and organic acids including acetic acid (AA), citric acid (CA) and tartaric acid (TA) at concentrations of 0 and 10 mmol kg-1. The soil was amended with five levels of 0, 100, 200, 300 and 400 mg kg-1 lead from lead nitrate source. The experiment was conducted as factorial based on completely randomized design with three replications. The results showed that the shoot dry weight was higher in organic acids treatments than synthetic chelates, and increasing of lead concentration up to 300 and 400 mg kg-1 decreased shoot dry weight. Acetic acid significantly increased the available lead concentration in the soil and the highest amount was obtained at level of 400 mg kg-1 lead in soil. The highest plant extraction potential was observed with acetic acid at 100 mg kg-1. Organic acids showed more effective role in increasing the extraction of lead compared to the than chelates. The results of this study showed that Satureja hortensis had high ability to extract lead from soil at Pb levels of up to 200 mg kg-1. Due to the high translocation efficiency of lead from root to shoot, this plant can be used for soil remediation with application of organic acids.