THE POTENTIAL OF THE HIGH-BIOMASS NICKEL HYPERACCUMULATOR BERKHEYA-CODDII FOR PHYTOREMEDIATION AND PHYTOMINING

Pot trials and tests in outside plots were carried out on the South Af rican Ni hyperaccumulator plant Berkheya coddii in order to establish its potential for phytoremediation of contaminated soils and for phyto mining of Ni. Outside trial plots showed that a dry biomass of 22 t/ha could be achieved after moderate fertilisation. Pot trials with varyi ng soil amendments with nitrogen and phosphorus fertilisers showed enh anced uptake of Ni with increasing nitrogen addition, though there was no reaction to phosphorus. The Ni content of the plant was directly r elated to the ammonium acetate extractable fraction of Ni in a wide ra nge of natural and artificial substrates. Excision of shoots induced a dramatic increase in the Ni content in the new growth (5500 mu g/g co mpared with 1800 mu g/g Ni). When plants were grown in pots with Ni ad ded to the substrate (0-1%), the Ni content of the plants rose to a ma ximum value of about 1% dry mass. The data from this last experiment w ere used to calculate the probable Ni yield (kg/ha) of plants grown in nickel-rich soils in different parts of the world. It was calculated that moderately contaminated soils (100 mu g/g Ni) could be remediated with only two crops of Berkheya coddii. The potential of this species for phytomining has also been evaluated and it is proposed that a yie ld of 100 kg/ha of Ni should be achievable at many sites worldwide. Ph ytomining is also discussed in general terms for other metals as well as Ni. (C) 1997 Elsevier Science B.V.