Challenges and potential approaches for soil recovery in iron open pit mines and waste piles

The revegetation of areas impacted by iron mining may be hampered by a series of chemical and physical impediments exhibited by those areas. Physical problems, such as penetration resistance and steep slopes, may outweigh the chemical problems, such that both should be considered for soil recovery. This study aimed to evaluate the main soil attributes that are directly related to plant growth on areas affected by iron mining activities discussing possible solutions. For this purpose, chemical and physical attributes including penetration resistance on open pit mines, waste piles and native forest in Carajas Mineral Province were analysed. The results show that the open pits had low to medium levels of P and low levels of organic matter and of the micronutrients B, Zn and Cu. In the waste piles, the chemical parameters were less hindering than in the open pits. Soil penetration resistance in open pits was higher than in the waste piles and the forest; however, there was a reduction of up to 69% in soil resistance in open pits in the rainy season. The principal chemical problems observed in mine pits can be easily corrected, although the inclination of open pit slopes in combination with elevated soil density increase the risks of losses of fertilizers and seeds by runoff. Penetration resistance is the most serious problem for the development of plants in mine pits, although the use of irrigation water can help to maintain tolerable levels of resistance in soil for proper root growth of native species.