Rehabilitation studies on an old non-ferrous waste dumping ground: effects on revegetation and metal immobilization by beringite

Abstract

The possibility of restoring a vegetation on a bare, industrial dumping ground, strongly contaminated by several non-ferrous metals, was studied. The potential beneficial effect of this restoration on metal leaching was estimated. On a laboratory scale, the high phytotoxic potential of the dump's surface substratum could be reduced significantly by the addition of 5% beringite, a substance characterised by a strong metal fixing capacity. On surface plots in situ, beringite and/or compost were mixed in the upper 30 cm top layer of the dumps substratum, and a seed mixture of selected metal-tolerant plants was sown. A healthy and well closed vegetation developed. Beringite addition to the substratum in situ caused a significantly lower metal content in the aerial parts of the plants. Semi-field simulations of percolation showed that the beneficial effect of a vegetation cover was marked: the amount of percolating Zn and Cd was reduced with more than 85%. Beringite addition significantly enhanced the volume of percolated water; the metal concentration in this percolate was, however, much lower than in percolates from the same substrate without beringite addition. It was concluded that the risk of both lateral wind erosion and percolation of metals from the waste dumping ground could be strongly reduced by a revegetation of its surface with metal-tolerant plants.