EFFECTS OF HEAVY METALS, CONTAINED IN FLOTATION TAILINGS, ON PLANTS USED IN REVEGETATION

Abstract

During the processing of precious and base metal ores from the Baia Mare mining area, which contained Au, Ag, Cu, Pb and Zn, large amounts of flotation tailings resulted, which were deposited in the Bozânta tailings management facility, located between Săsar and Bozânta Mare villages, 4 km west of Baia Mare. Due to the presence of minerals containing metal sulphides (mainly pyrite), the acid rock drainage (ARD) has become very active, catalysed by iron- and sulphur-oxidizing bacteria, which naturally occur at these sites. Decreasing the surface of the pond as a result of evaporation, combined with the increase of the beach surface and the absence of any protection at the embankment ridge, led to the entrainment of the tailings by wind at considerable distances. They often end up in neighbouring settlements, especially in the two mentioned villages, as a result of prevailing winds from the NE-SW direction. The purpose of the research was to test the resistance of some plant species (Sinapis alba L. – white mustard; Trifolium pratense L. – red clover and Lolium perenne L. – ray grass) to the conditions generated by the tailings on the surface of the depot, in order to create a vegetation cover with a role in diminishing tailings discharges in the adjacent areas. There were tested the effects of the industrial eluate (acid mine water, pH 4.3), obtained from the tailings pond, over seed germination parameters: germination capacity (GC); germinative energy (GE) and relative seed germination (RG). The results of the tests pointed out that the least affected was white mustard: GC – 95.3%; the differences in the values obtained in the control samples and the GE test – 5.3%; the results for RG – 99.3%, confirm that the white mustard seeds were the least influenced by the industrial eluate, followed by ray grass and red clover. In the tests for plant growth on the tailings pond, 5 experimental variants were used: a) soil (S); b) flotation tailings (T); c) mixture of flotation tailings and soil (T+S); d) mixture of flotation tailings and organo-zeolitic material (T+OZ); e) mixture of flotation tailings, organo-zeolitic material and soil (T+OZ+S). It is recommended to use the T+OZ+S mixture on the pond surface and sowing with Sinapis alba and Trifolium pratense. For both species, double seed sowing is recommended.