PETRONELA-BIANCA PAVEL, ELENA DIACU, CONSTANTIN HORIA BARBU LONG-TERM EFFECTS ON THE FRACTIONATION AND MOBILITY OF HEAVY METALS IN A POLLUTED SOIL TREATED WITH BAUXITE RESIDUES
The main purpose of this study was to evaluate the efficiency of red mud (a bauxite residue) used as amendment to immobilize the metals present in a polluted soil and to assess the fractionation and mobility of the metals in soil after 6 years since red mud addition. In this context, the seven-step sequential extraction procedure (SEP) of Zeien and Brümmer was performed in order to investigate the mechanisms of metals in soil after the red mud addition. The analysis of heavy metals mobility (Zn, Cd and Pb) through sequential extraction showed a significant reduction of the metals concentrations in the mobile fraction (F1) and an increase of the metal concentration bounded to the less mobile fractions, the amorphous and crystalline Fe- oxides (F5 and F6). The red mud addition to soils caused a pH increase of the soil, up to 2 pH units (e.g. from 5 to 7) and had a pronounced effect in lowering the metal mobility in soil relative to the soil without the immobilizing amendment.
Keywords: red mud, heavy metals, immobilization, sequential extraction procedure