Abstract
A soil cover system can be viewed as a thin interface placed between the atmosphere and the underlying waste. Climate is a primary design variable in soil cover design; therefore, climate change poses a number of challenges to design, operation and long-term performance of covers. In this research climate change effects on the hydraulic behavior of soil covers at a Northern Ontario, Canada site were assessed. Covers were analyzed using historical and future climate datasets. Historical climate data were compiled from an Environment Canada weather station near the site. The future climate datasets were sourced for different Global Circulation Models (GCM) for various representative concentration pathways (RCP). The covers at the site were constructed with a single layer of desulphurized tailings. Soil covers were meant to limit oxygen ingress to the underlying reactive tailings by maintaining high water saturation in the covers. Oxygen flux through soil covers for current and future climates were predicted using variably saturated water flow and oxygen transport modeling using the finite element method. The results of this research indicate that the effect of climate change on soil cover depends on the hydraulic properties of the soil cover materials and that of the underlying tailings. The results of this study suggest that the effect of climate change on the coarse tailing covers could be marginal resulting in a maximum increase of 5% in oxygen flux at the cover surface for the future climates in comparison to the base climate. However, in the case of fine tailings covers, increases of up to 65% can be expected.
Highlights
The generation of acid mine drainage (AMD) from sulphide enriched tailings has been a significant environmental challenge within mining industries related to hard rock [1]
Climate change poses a number of challenges to the design, operation and long-term performance of covers [14]
That the coarse tailings cover a considerable amount of oxygen flux at the tailings–cover interface was predicted; the results indicate that their performance will not deteriorate with changing climate (Figure 11)
Summary
The generation of acid mine drainage (AMD) from sulphide enriched tailings has been a significant environmental challenge within mining industries related to hard rock [1]. The sulphide mineral of heavy metals (e.g., iron, copper, gold, etc.) in the rock has the potential to react with oxygen and water. This reaction results in the tailings exhibiting acidic behavior, and increases the concentration of soluble metals. By limiting the supply of oxygen to the reactive tailings, one can control the production of AMD and reduce the risk. This risk can be further reduced if multiple strategies are used in an effective manner to limit the oxidation of the sulphide mineral.
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