The use of metal tolerant plant populations for the reclamation of metalliferous wastes
Published source details
Smith R.A.H. & Bradshaw A.D. (1979) The use of metal tolerant plant populations for the reclamation of metalliferous wastes. Journal of Applied Ecology, 16, 595-612.
Published source details Smith R.A.H. & Bradshaw A.D. (1979) The use of metal tolerant plant populations for the reclamation of metalliferous wastes. Journal of Applied Ecology, 16, 595-612.
Metalliferous wastes produced by mining and smelting heavy metals are difficult to reclaim, often due to heavy metal (e.g. lead, zinc or copper) toxicity and other substrate characteristics, such as nutrient deficiency, unfavourable for plant establishment and growth. Nutrient deficiencies can be dealt with by fertilizer application but heavy metal toxicity cannot be so readily overcome. Two potential mitigation techniques are to: cover the waste with a thick layer of inert non-toxic material e.g. soil or colliery shale (effective but expensive), or to introduce heavy metal tolerant plants (as investigated here).
Samples of waste material from 39 sites in England Scotland and Wales (with an additional three from Belgium) were analysed for lead, zinc, copper and calcium, potassium, phosphorus and nitrogen, and PH was determined.
A series of field experiments, sowing a range of grass species and their cultivars (cv) at a large number of mine sites monitored over 9-years, were undertaken.
Grasses naturally tolerant/adapted to the adverse growing conditions (e.g. some forms of red fescue Festuca rubra) grew faster and persisted longer than the commercial varieties sown, providing good stabilizing cover where adequate fertilizer was applied. Over the 9-year experimental period, the natural grasses persisted with little loss of vigour, even with minimal fertilizer treatment. The most important factor influencing species composition appeared to be pH, and those soil characteristics associated with it, rather than the type and content of metal present.
The most successful grasses at each site were those with the highest tolerance to the metals occurring in the waste, provided that the species was appropriately adapted to the other prevailing soil conditions governed primarily by pH.
Three cultivars (cv) are now commercially available which are tolerant to: acid lead/zinc wastes (common bent Agrostis (capillaris) tenuis, cv. Goginan), calcareous lead/zinc wastes (Festuca rubra, cv Merlin) and copper wastes (A.tenuis, cv Parys). These enable stabilization of a wide variety of acidic, calacareous, and/or toxic wastes.