Evolution of Chemical Characteristics of Technosols in an Afforested Coal Mine Dump over a 20‐year Period

Abstract

Coal mining in areas containing pyritic materials frequently leads to a remarkable impact on the environment because of sulphide oxidation. We studied the evolution of chemical characteristics of Technosols derived from sterile materials, in a lignite mine located in As Pontes (northwest Spain), over a 20-year period. Three plots, which had different management practices, were selected. The mine spoil was deposited randomly in two of the plots (CSP with low S concentration and CSA with high S concentration), while it was selectively managed in the other one (P206). Twenty years after the first sampling, CSA continued to show the highest acidity (pH water 3•7-3•9), whereas the lowest acidity was that of P206 (pH water 5•0). Regarding the surface layer, C increased 1•1% in P206, 0•3% in CSP and 0•2% in CSA. Nitrogen increased 1% in P206. The C/N ratio increased in all plots. Phosphorus, Ca, Mg, K and effective cation exchange capacity decreased in 2002 and experienced a slight increase in 2012. Exchangeable Al and Al saturation increased in CSP and P206 and decreased in CSA. Electric conductivity levels of Ca, Mg, Na, Al and SO 4 2À concentrations decreased in the soil solution in all plots during the 20-year period. Twenty years after the first monitoring, the plots that were built based on selective management of the mine spoil showed lower acidity and acidity-derived consequences. These facts confirm the necessity of an appropriate selection of sterile materials, avoiding the placement of pyrite-rich spoils on the surface or near-surface zones, which is essential to facilitate proper restoration of this kind of dumping areas.

Groundwater vulnerability assessment in degraded coal mining areas using the AHP–Modified DRASTIC model

“…Elevated nitrate concentrations in groundwater may be directly attributed to the explosives used for blasting purposes, which contain nitrate compound as a parent material. In addition to higher values of nitrate concentrations in mining areas, the results also revealed high values of SO 4 concentrations in the groundwater samples of the mining areas; these high values are attributed to the oxidative weathering of pyrites in mining areas (Rivas‐Pérez et al, ). SO 4 concentrations in the study area varied from 8 to 379 x 10 −3 kg/m 3 , with a mean concentration of 172 x 10 −3 kg/m 3 .…”

Selection of forest species for the rehabilitation of disturbed soils in oil fields in the Ecuadorian Amazon

“…However, they would require permanent care if they were to reach their maximum growth, and their selection ought to be based on the ecological benefits they may produce. This would also be an investment in better soil water management, as forests restored in similar degraded lands (such as mines) will contribute to the reduction of runoff and to the improvement of soil quality (Mukhopadhyay and Maiti, 2014;Buendia et al, 2016;Jiménez et al, 2016;Rivas-Pérez et al, 2016), reducing the off-site detrimental effects these mining and oil extraction activities may have (e.g., export of contaminated sediments and polluted water).…”

Stability and characterisation of spoil heaps in European surface lignite mines: a state-of-the-art review in light of new data

“…Lastly, different minerals have varying solubility levels and hence basic or acidic environments can develop within the slope. For example, sulphide minerals can increase the acidity of the soil (Nyssen and Vermeersch 2010), while carbonate minerals act as a buffer, hence retarding the acidity (Rivas-Pérez et al 2016;Schreck 1998). Studies have reported pH levels as low as 2.5 (Schreck 1998) which can speed up the mineral degradation of the spoil and hence endanger the long-term stability of the slopes.…”