Résumé - Abstract
The aim of this project is to evaluate the potential impacts of the proposed application of an elevated water table (EWT) technique on partially oxidized tailings of Mine Principale (Parc B), Chibougamau, Québec. The EWT technique, which usually involves raising the water table and maintaining it above reactive tailings, has been confirmed to limit sulfide-mineral oxidation by minimizing oxygen gas ingress into the tailings since oxygen gas has low diffusivities in saturated media. The EWT, however, has the potential to cause direct dissolution of soluble secondary phases, but also can potentially induce reducing conditions that are ideal for microbial-mediated reductive dissolution of Fe(III) oxyhydroxide phases. Direct dissolution of soluble secondary phases and reductive dissolution of Fe(III) oxyhydroxide phases can result in the release of the associated metal(loid)s that can be detrimental to the environment. Recent selective chemical extraction procedures that were conducted on sampled cores collected from Parc B indicated significant presence of toxic metal(loid)s on Fe(III) oxyhydroxide phases. The next step is to characterize these Fe(III) oxyhydroxide phases and the microbial species (e.g., iron-reducing bacteria) that may influence the reductive dissolution reactions of Fe(III) oxyhydroxide phases. Characterization of the minerals, including Fe(III) oxyhydroxide minerals, will be done using mineralogical study while the presence of the microbial species will be determined through microbial DNA analysis that was recently extracted using DNeasy PowerSoil Pro Kit. Finally, a reactive transport model, MIN3P, will be utilized to simulate the application of EWT system and the potential release of metal(loid)s from secondary phases. The results will be used to evaluate the suitability of the EWT system in Mine Principale.