GEOLINKS International Conference 2019, Book 3
ECOLOGY AND ENVIRONMENTAL STUDIES
IN-SITU PHYTOEXTRACTION OF NICKEL BY ODONTARRHENA SERPYLLIFOLIA ON ULTRAMAFIC SOILS OF PORTUGAL
Prof. Dr. Paulo J. C. Favas, Prof. Dr. João Pratas
Serpentine soils derived from ultramafic rocks have a worldwide distribution. These soils are rich in nickel (Ni), chromium (Cr) and sometimes cobalt (Co), but are poor in essential nutrients, such as nitrogen (N), phosphorus (P), potassium (K) and calcium (Ca). Plants that hyperaccumulate Ni colonize serpentine soils as endemics. The rhizosphere of these endemic plants provides a complex and dynamic microenvironment where the roots, along with associated microorganisms, form unique ecosystem with an extraordinary phytoextraction function. This study considers the use of serpentine soils in Northeast Portugal as potential producers of Ni using an endemic species (Odontarrhena serpyllifolia) for phytomining. In this sense, the present study had the following objectives: (1) to investigate the relationship between Ni concentration in the soil and the concentration in the plant (O. serpyllifolia) in ultramafic areas of Portugal; and (2) to assess the potential of this species for Ni phytomining as bio-ore. This species is endemic to serpentine soils of the Bragança and Morais massifs and is a Ni hyperaccumulator that can accumulate more than 12,000 mg/kg (dry weight). Under natural conditions, the results show that considering only the aerial parts of the plant, the biomass varies between 4.08–9.37 t/ha, containing a range of 0.25–1.23% Ni, allowing a withdrawal of between 12.2–98.1 kg Ni/ha per crop under natural conditions. The amount of Ni extracted by the plant is similar in both ultramafic areas, having a mean value of approximately $US 500 per ha considering the January 2019 Ni prices. The results of this study indicate that some of the land in these ultramafic areas are potential producers of Ni from this endemic species.
gromining, bio-ore, hyperaccumulation, phytomining, serpentine flora