Abstract
The São Domingos mine is within the Iberian Pyrite Belt, a mining district with large concentrations of polymetallic massive sulfide deposits. Mine waste heaps are considered extreme environments, since they contain high total concentrations of potentially hazardous elements (PHE), which contribute to inhibiting the development of most plants. Autochthonous plant species, such as Cistus salviifolius L., are able to grow naturally in this degraded environment, and may contribute to minimizing the negative chemical impacts and improving the landscape quality. However, the environmental rehabilitation processes associated with the development of these plants (phytostabilization) are very slow, so the use of materials/wastes to improve some physicochemical properties of the matrix is necessary in order to speed up the process. This work studied the effectiveness of the phytostabilization with C. salviifolius of gossan mine wastes from the mine of São Domingos amended with organic and inorganic wastes in order to construct Technosols. The mine wastes have an acid pH (≈3.5), high total concentrations of PHE and low concentrations of organic C and available nutrients. The best vegetative development occurred without visible signs of toxicity in the Technosols containing a mixture of agriculture residues. These treatments allowed the improvement of the soil-plant system providing a better plant cover and improved several chemical properties of mine wastes, helping to speed up the environmental rehabilitation.
Highlights
The Iberian Pyrite Belt (IPB) is one of the most important volcanogenic massive sulfide ore deposits in the world [1], and it is located in the southwest of the Iberian Peninsula
The oxidation of the metallic sulfides included in some mine spoils results in acid mine drainage (AMD) with the consequent release and leaching of significant amounts of potentially hazardous elements (PHE) leading to the contamination of the surrounding soils and the alteration or destruction of the adjacent ecosystems [7,8,9]
The original gossan wastes were amended with a mixture of organic/inorganic wastes from agriculture (OR) and biomass ashes (BA), an inorganic residue from a thermoelectric station, and a mixture of both (BA + OR)
Summary
The Iberian Pyrite Belt (IPB) is one of the most important volcanogenic massive sulfide ore deposits in the world [1], and it is located in the southwest of the Iberian Peninsula. In the IPB mines, as a result of open cast and underground mining operations, large amounts of waste materials with high contents of potentially hazardous elements (PHE) have been exposed to weathering and pedogenesis conditions leading, in some areas, to the formation of incipient soils (Toxic Spolic Technosols, [5]). These soils, as well as the mine wastes, have substantial chemical and physical limitations, such as low organic matter and nutrient contents in the available fraction and low pH, unfavourable texture and structure and high total content of PHE [6]. The transfer of chemical elements among the different solid phases contributes to controlling their behavior, mobility and availability
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