Evolution of sulfide oxidation and attenuation mechanisms controlling acid mine drainage in decommissioned low-sulfide tailings

Annika Parviainen

    Research output: ThesisDoctoral ThesisCollection of Articles

    Abstract

    Environmental hazards derived from mining have been a major concern worldwide in the past years. Understanding of the consequences of malpractice in waste management and the lack of aftercare is crucial to the sustainability of the future mining industry. Mineralogical and geochemical studies are key to predicting the generation of acid mine drainage (AMD) and to evaluating the stability of a tailings system at an advanced stage of weathering. Site-specific data also assist in selecting the remediation scheme for decommissioned tailings. This thesis examines the evolution of sulfide weathering and the natural attenuation mechanisms controlling AMD at the Haveri Au-Cu and Ylöjärvi Cu-W-As mine tailings (SW Finland). Environmental investigations of this scale at decommissioned tailings have not been performed in Finland before. A combination of traditional mineralogical methods (optical microscopy, electron microscopy, X-ray diffraction), advanced synchrotron-based techniques, as well as geophysical and geochemical studies assessing elemental dispersion in the tailings (electric resistivity tomography, sequential extraction of solid tailings and water chemistry) provided a comprehensive data set and proved essential for evaluating the retention capacity and stability of secondary Fe(III) minerals in vadose tailings. Further, a study on the geochemistry of lake sediment records from the catchment receiving mine effluents allowed assessment of the long-term impact of AMD. Half a century after mine closure, the shallow tailings at Haveri and Ylöjärvi had undergone extensive sulfide weathering, mobilizing potentially toxic elements, e.g. As, Co, Cu, Ni, and Zn. Lake sediment data showed that elemental transport had decreased from the contamination peaks to values slightly above the background level. However, at Ylöjärvi high As contents were recorded in pore and groundwater samples. Fe(III) minerals played an important role as a sink for As and divalent cations through adsorption (minor component) and co-precipitation, and cemented layers with accumulations of these phases, detected at both sites, contributed to the natural attenuation processes. Jarosite and goethite trapped As, Cu and SO4 at the low pH (2.5-3.5) in the Haveri tailings, whereas arsenical ferrihydrite, hydrous ferric arsenate, scorodite, and kankite retained As, Co, and Cu at the near neutral pH (4.9-8.9) at Ylöjärvi. The Fe(III) minerals proved important for As retention in altered samples, where the As content in the secondary minerals' fractions approached 90-100% of the total in sequential extractions. The results indicated that mine waters at the sites deteriorate the water quality at present despite the attenuating processes and also give indication of adequate remediation techniques.
    Translated title of the contributionSulfidien hapettuminen ja pidättymismekanismit happamien kaivosvesien kontrolloijana suljetuilla rikastushiekka-alueilla
    Original languageEnglish
    QualificationDoctor's degree
    Awarding Institution
    • Aalto University
    Supervisors/Advisors
    • Leveinen, Jussi, Supervising Professor
    • Loukola-Ruskeeniemi, Kirsti, Thesis Advisor, External person
    • Nieto Liñán, José Miguel, Thesis Advisor
    Publisher
    Print ISBNs978-952-60-4741-6
    Electronic ISBNs978-952-60-4742-3
    Publication statusPublished - 2012
    MoE publication typeG5 Doctoral dissertation (article)

    Keywords

    • mine tailings
    • sulfide oxidation
    • acid mine drainage
    • arsenic
    • trace elements
    • secondary Fe(III) minerals
    • natural attenuation
    • Haveri
    • Ylöjärvi

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