Comparision of heavy metals removal from comtaminated soil by siam weed (Chromolaena odorata) and vetiver grass (Vetiveria zizanioides)

Abstract

The ability on heavy metals removal by C. odorata and V. zizanioides grown on contaminated soil and synthetic contaminated soil in experimental pots was investigated. Both contaminated and uncontaminated soils for preparing the synthetic contaminated soil in this study were obtained from Mae Sot district, Tak province. For the contaminated synthetic soil was prepared by adding solution of cadmium nitrate, zinc sulfate, lead nitrate, and copper sulfate to uncontaminated soil to make up the concentration of each metals: Cd, Zn, Pb, and Cu to be 100 mg/kg soil above their initial concentrations. In both plants grown on the on-site contaminated soil and on the synthetic soil, although some abnormal symptoms such as chlorosis, scorching in leaves and necrosis appeared, the plants still grew well. Each part of the plant was examined for heavy metal uptake according to time of planting, 30, 60, 90 and 120 days. Root uptake was greater than that of stem and leaves in all samples. For the on-site contaminated soil, the highest concentrations found in the root part for Cd, Zn, Pb and Cu of C. odorata were 50.22, 123.45, 29.07 and 31.89 mg/kg on a dry weight basis, respectively and of V. zizanioide were 11.24, 163.18, 40.63 and 15.62 mg/kg on a dry weight basis, respectively. For the synthetic contaminated soil were also found higher concentration in root part than the other two parts for all metals both in C. odorata and in V. zizanioide. This is due to metals existed in synthetics soil was readily in available form. To compare accumulation of Cd in mass in for both plants grown in contaminated soil by the time of harvesting, the results showed that, C. odorata performed better than V. zizanioide, especially for the aboveground parts and the suitable time for harvesting that yielded the highest uptake of Cd was at 120 days.