IODIDE FOR THE PHYTOEXTRACTION OF MERCURY CONTAMINATED SOIL

Garden cress (Lepidium sativum) plants were grown in soil artificially contaminated with mercury salts: HgCl2, HgSO4, Hg(NO3)(2). Laboratory investigations were performed to evaluate the accumulation of Hg in roots, stems and leaves of the plant before/after iodide amendment to the soil. The result showed that Lepidium sativum accumulated mercury from soil, but overall maximum concentration of mercury was found in roots of the plants. Iodide application to the soil caused mercury mobilisation and thereby increased the bioavailability of Hg in soil, which effected in increase of Hg concentration in the plant. Effective accumulation by whole plant and by shoots was higher compared to the process, which was carried out without iodide addition. Enhancing the phytoextraction by addition of potassium iodide increases the efficiency of the process. In spite of using soil amendment (KI), over 80% of total mercury concentration in Lepidium sativum was accumulated in roots of the plant. Therefore this plant has a potential to be a good phytostabilizer. Lepidium sativum is an important medicinal plant and a vegetable consumed by people, for that reason there is a possibility of including Hg into food-chain. Toxicological risks should be consider before using this plant for cleaning soil contaminated by Hg.