USE OF METAL TOLERANT PLANT-POPULATIONS FOR THE RECLAMATION OF METALLIFEROUS WASTES

A survey was made of metalliferous mine wastes in Great Britain. The results suggest that high concentrations of toxic metals are the major cause of sparse vegetation cover, but comparisons of bare and adjacent vegetated areas suggests that phosphorus concentrations are the immediate determinant. Field experiments, using a range of grass species at a large number of mine sites, showed that naturally occurring tolerant populations grew faster and persisted longer than normal commercial varieties. They provide an excellent stabilizing cover, provided adequate fertilizer was given, and have persisted for 9 years with little loss of vigour, even with minimal fertilizer treatment. The most successful populations at each site were those with the highest tolerance to the metals occurring in that waste, provided that the species was appropriately adapted to the other soil conditions occurring there. Three cultivars are now commercially available which are tolerant to: acid lead/zinc wastes (Agrostis tenuis, cv Goginan), calcareous lead/zinc wastes (Festuca rubra, cv Merlin) and copper wastes (Agrostis tenuis, cv Parys). These enable stabilization of a wide variety of wastes.