REHABILITATION STUDIES ON AN OLD NONFERROUS WASTE DUMPING GROUND - EFFECTS OF REVEGETATION AND METAL IMMOBILIZATION BY BERINGITE

The possibility of restoring a vegetation on a bare, industrial dumpin g ground, strongly contaminated by several non-ferrous metals, was stu died. The potential beneficial effect of this restoration on metal lea ching was estimated. On a laboratory scale, the high phytotoxic potent ial of the dump's surface substratum could be reduced significantly by the addition of 5% beringite, a substance characterised by a strong m etal fixing capacity. On surface plots in situ, beringite and/or compo st were mixed in the upper 30 cm top layer of the dumps substratum, an d a seed mixture of selected metal-tolerant plants was sown. A healthy and well closed vegetation developed. Beringite addition to the subst ratum in situ caused a significantly lower metal content in the aerial parts of the plants. Semi-field simulations of percolation showed tha t the beneficial effect of a vegetation cover was marked: the amount o f percolating Zn and Cd was reduced with more than 85%. Beringite addi tion significantly enhanced the volume of percolated water; the metal concentration in this percolate was, however, much lower than in perco lates from the same substrate without beringite addition. It was concl uded that the risk of both lateral wind erosion and percolation of met als from the waste dumping ground could be strongly reduced by a reveg etation of its surface with metal-tolerant plants.