Both sectors of the Iberian Pyrite Belt, Portuguese and Spanish, have been exploited since ancient times, but more intensively during and after the second half of the 19th century. Large volumes of polymetallic sulfide ore were extracted in open pits or in underground works, processed without environmental concerns, and the generated waste rocks and tailings were simply deposited in the area. Many of these mining sites were abandoned for years under the action of erosive agents, leading to the spread of trace elements and the contamination of soils, waters and sediments. Some of these mine sites have been submitted to rehabilitation actions, mostly using constructive techniques to dig and contain the contaminated tailings and other waste materials, but the remaining soil still needs to be treated with the best available techniques to recover its ecosystem functions. Besides the degraded physical structure and poor nutritional status of these soils, they have common characteristics, as a consequence of the pyrite oxidation and acid drainage produced, such as a high concentration of trace elements and low pH, which must be considered in the remediation plans. This manuscript aims to review the results from studies which have already covered these topics in the Iberian Pyrite Belt, especially in its Portuguese sector, considering: (i) soils’ physicochemical characteristics; (ii) potentially toxic trace elements’ concentration; and (iii) sustainable remediation technologies to cope with this type of soil contamination. Phytostabilization, after the amelioration of the soil’s properties with organic and inorganic amendments, was investigated at the lab and field scale by several authors, and their results were also considered.

Pinewood biomass in Portugal can be considered a major source of biochar for soil physical, chemical, and biological edaphic amendment. This work intended to evaluate the aptitude of lab produced biochar for upgrading soil moisture dynamics’ relationships considering mixtures of biochar with silica-based sand. The methodology used focused on the carbonization of pine biomass with inert atmosphere at 300 °C, 400 °C, 500 °C and 600 °C, followed by a chemical proximate and thermogravimetric analysis, scanning electron microscopy, Fourier Transform Infrared analysis, numerical modeling, and characterization of biochar porosity by gas adsorption (Brunauer–Emmett–Teller) and mercury porosimetry. The results showed the increased amounts of soil water retention and plant available water, evaluated through pF curves, due to biochar application. The thermogravimetric analysis mass loss patterns and FTIR transmittance, reflected major structural modifications in carbonized products by comparison with raw biomass. Mercury porosimetry showed that biochar pores between 392 and 250 μm and 32 μm and 6 μm gave the highest pore volume for water retention with a major increase from carbonization, by comparison with physical activation. The used methodologies allowed us to conclude that the carbonaceous feedstock can potentiate the improvement of soil water relations aiming at agricultural land use.

Pinus pinea is widely distributed in the Mediterranean basin. In Portugal, it is predominantly located in the southwestern coastal area. Yet, there are also forest areas of Pinus pinea in inland southern Portugal. Four plots were settled to study the effects of soil chemical characteristics, air temperature and precipitation on Pinus pinea growth. In these plots, stand structure, soil texture, soil organic matter, soil content on macronutrients and micronutrients, air temperature and precipitation were analysed. The results indicate that the greatest growth was achieved in the plots with good availability of nutrients and the highest precipitation, whereas the lowest growth was observed in the plots with the lowest precipitation. There seems to be a trend toward the main limiting factor to Pinus pinea growth being the availability of water.