Fractionation of Mercury in Water Hyacinth and Pondweed from Contaminated Area of Gold Mine Tailing

The ability of water hyacinth (WH) and pondweed (PW) to accumulate mercury from water in gold mine tailing area was studied. Experiments were carried out in the field conditions without using a model system. An approach for mercury fractionation according to its association with various types of biomolecules (water soluble compounds, oxygen-containing ligands such as polycarboxylic acids and cell wall components) was suggested. It is based on sequential extraction of mercury to recover different compounds according to the binding strength. In all cases for WH and PW, the most portion of mercury is bound to the cell wall (63-67 and 54-64 %, for WH and PW, respectively) that works as a physiological bafflers and protects the plants from negative impact of mercury ions. An approach based on the ability of plants to extract elements from tailings drainage waters that are characterized by milder conditions in comparison with strongly acidic waste material was suggested. The highest BCF values (66,500 and 32,700 for WH and PW, respectively) were obtained for plants grown in natural stream. At low levels of mercury in water (C Hg-water = 0.01-0.05 ppb) typical for tailing solutions. translocation of the element from roots to shoots decreases as concentration of mercury in WH increases. PW is preferable to use in practice for tailings remediation from mercury contamination since it does not require cultivation in a greenhouse and shows BCF values comparable with WH.