Morais Ultramafic Complex: A Survey towards Nickel Phytomining

Ultramafic areas are critical for nickel (Ni) phytomining due to the high concentration of this element in their soils and the number of hyperaccumulators they harbor. The aim of the present study was to evaluate the potential of the Morais massif, an ultramafic area in Portugal, for phytomining using the hyperaccumulator species Alyssum serpyllifolium subsp. lusitanicum. Soil samples and A. serpyllifolium specimens were collected in four locations of the Morais massif. After determination of Ni concentrations in the samples, the results show that soil pseudo-total Ni concentrations in sites number 1 and 2 are significantly higher than in the soil samples collected in the other two locations, with 1918 and 2092 mg kg−1, respectively. Nickel accumulation is significantly greater in the aerial parts of plants collected at sites 1, 2, and 4, presenting Ni harvestable amount means of 88.36, 93.80, and 95.56 mg per plant, respectively. These results suggest that the sites with highest potential for phytomining are sites 1, 2, and 4. A nickel agromining system in these locations could represent an additional source of income to local farmers, since ultramafic soils have low productivity for agriculture and crop production.

Nickel accumulation by Alyssum serpyllifolium subsp. lusitanicum (Brassicaceae) from serpentine soils of Bragança and Morais (Portugal) ultramafic massifs: plant–soil relationships and prospects for phytomining

The aim of the present study was to evaluate the possibility of using Alyssum serpyllifolium Desf. susbp. lusitanicum T.R.Dudley & P.Silva (Brassicaceae) for phytomining nickel (Ni)-rich bio-ore from serpentine soils. This species is endemic to serpentine soils of the Bragança and Morais massifs and is a Ni hyperaccumulator, containing more than 7000 mg kg–1 (dry weight) of this element. The variability of the Ni concentrations contained in the plant at different locations was verified as was its relationship with the total Ni contained in the soil or with the bioavailable Ni fraction extracted with ammonium acetate. We evaluated the biomass produced under natural conditions, and, on the basis of these values, we estimated the amount of Ni that can be removed per unit area. The results showed that considering only the aerial parts of the plant, the biomass varies between 7.04 and 9.37 t ha–1, containing a range of 0.12–0.70% Ni, allowing a withdrawal of between 12.2 and 44.0 kg Ni ha–1 per crop under natural conditions.