Comparison phytoremediation Potential of Pb from Contaminated Soil by Vetiveria zizanioides and Brassica oleraceae

Soil contamination is one of the most important pollutants in the environment. Lead (Pb) is one of the heavy metals and important pollutant in arid ecosystem. The use of plants to remove contaminated soil or Phytoremediation is an economical method. Todays due to increasing the pullution of soil sources and resultant problems, identification the resistant plant species against soil pollution is essential. Effeciency of Vetiver and Brassica to Pb uptake has not studied and compared, therefore, this study was carried out in order to compare the Phytoremediation capacity of Pb by two plants i.e. Vetiveria zizanioides and Brassica oleraceae, and to indentify the better specie for this purpose.

A completely randomized design with factorial arrangement in greenhouse conditions was carried out. Treatments included two types of plants (Vetiveria zizanioides and Brassica oleraceae) and three rates of Pb contamination in soil (50, 250 and 500 mg / kg prepared from lead nitrate) in three replicates. After measuring the amount of Pb in soil by DTPA, the concentration of Pb in root and shoot of plants, Translocation factor (translocation from roots to shoots) and Bio-accumulation factor (translocation from soil to roots) were measured, too. Data analysis was performed using JMP software and comparison of means by LSD method.

The results of analysis of variance showed that the effect of plant type, soil contamination rates and their interaction on accumulation content of lead in root and soil were Significant at p < 0.01, while the effect of soil contamination rate on the shoots of plant was Significant at p < 0.05. The highest accumulation contents of lead in roots and shoots were found in Vetiver plant containing 250 mg / kg of soil pollution rate treatment. Also, the highest amount of Pb accumulation in soil was related to Brassica containing 500 mg/kg of soil treatment. Vetiver in root and shoots accumulated Pb 3.5 and 2.1 times more than Brassica, respectively. In addition, the accumulation content of Pb in the roots of Vetiver was 4 times higher than its shoots, while the concentration of Pb in roots of Brassica was 1.5 times greater than its shoots. Translocation factor in both plant was less than 1, while bio-accumulation factor of Vetiver was greater than that of Brassica in all Pollution rates.

Despite the ability of both plants to accumulate lead in their roots and shoots, Vetiver had the better performance in lead uptake from soil and reduced lead amount in soil, so its application is recommended for Phytoremediation purposes.