Abstract
The geochemical characterization of the mine deposits and soils in metal mining areas is essential in order to develop an effective mine reclamation strategy. The determination of total potentially toxic element (PTE) content, together with the application of chemical extraction procedures, can give insight into the behavior of contaminants after the application of different mine reclamation solutions, as well as identify the areas where urgent action is needed. This work presents a practical application to the evaluation of the pollution potential of trace elements in soils affected by mining activities, to be used in metallic mine reclamation. The PTE behavior was assessed by single extractions in order to simulate four environmental conditions: PTE mobility under rainfall conditions, acid mine drainage, reducing conditions, and plant uptake. The spatial distribution of contaminants in the study area was evaluated by determination of PTE total content in soil samples. Trace elements with high natural mobility, such as Zn, appeared concentrated at water and sediment discharge areas, while As, Pb, and Cu contents were higher near the mine wastes. The results obtained after the extractions suggested that the highest PTE content was extracted in the complexing–reducing medium, due to the dissolution of secondary sulfates and Fe3+ oxyhydroxides and the subsequent release of PTEs associated with those mineral phases. Reclamation strategies applied in the study area should promote efficient water drainage, infiltration, and subsuperficial water circulation in order to maintain oxidant conditions in the soil. The methodology applied in this study may constitute a valuable tool to define the geochemical constraints in metal mining areas, as well as help to develop appropriate mine reclamation solutions.
Highlights
The long story of metalliferous mining, processing, and smelting activities in the Iberian Pyrite Belt has left behind a legacy of numerous abandoned mines and considerable quantities of waste rock piles, spoil heaps, and tailing ponds [1,2,3]
When oxidation of the sulfides remaining in those mine wastes occurs, it results in the generation of strongly acidic leakages and acid mine drainage (AMD), as well as the mobilization of considerable quantities of potentially toxic element (PTE) and trace elements such as Pb, As, Zn, Cu, Cd, or Hg, among many others, which can cause serious environmental impact [6,7]
Several studies have already remarked the high concentrations of PTEs in soils, sediments, and water bodies near mining sites and waste deposits in the Iberian Pyrite Belt [3,8,9,10]
Summary
The long story of metalliferous mining, processing, and smelting activities in the Iberian Pyrite Belt (southwest of the Iberian Peninsula) has left behind a legacy of numerous abandoned mines and considerable quantities of waste rock piles, spoil heaps, and tailing ponds [1,2,3]. When oxidation of the sulfides remaining in those mine wastes occurs, it results in the generation of strongly acidic leakages and acid mine drainage (AMD), as well as the mobilization of considerable quantities of PTEs and trace elements such as Pb, As, Zn, Cu, Cd, or Hg, among many others, which can cause serious environmental impact [6,7]. In this regard, several studies have already remarked the high concentrations of PTEs in soils, sediments, and water bodies near mining sites and waste deposits in the Iberian Pyrite Belt [3,8,9,10]. Drainage networks and groundwater environments have been found to be especially vulnerable to contamination by the release of PTEs from waste deposits [11], and their accumulation in flora and fauna can entail huge environmental problems [12,13,14,15,16]
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