Tackling mine waste for better environment / Régler le cas des rejets miniers qui minent l’environnement

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    Final technical report : management and stabilization of mining and industrial wastes (01/06/2009 - 1/06/2014)
    (2014-11) Benzaazoua, Mostafa; Hakkou, Rachid
    When mines close, the health and environmental risks of mine waste depends on their acid generating potential. Abandoned mines containing reactive tailings are especially problematic. The project team investigates new technologies for the recycling and valorization of non-polluting mine wastes. In terms of training, Cadi Ayyad University in Morocco and Université du Québec en Abitibi en Témiscamingue (UQAT) collaborate to create high-quality training opportunities in the field of mining environment research. A significant outcome is the restoration of the abandoned Kettara mine site, which had been leaching heavy metals into the soil and water table for decades.
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    Assessment of soil contamination around an abandoned mine in a semi-arid environment using geochemistry and geostatistics : pre-work of geochemical process modeling with numerical models
    (Elsevier, 2012) Khalil, A.,; Hanich, L.,; Bannari, A.,; Zouhri, L.,; Pourret, O.,; Hakkou, R.
    One of the most serious environmental issues related to mining industry in Morocco and elsewhere around the world, is the pollution from abandoned mine sites. Mine wastes cause obvious sources of soil contaminations. Climatic effects such as heavy rainfall engender metal dispersion in semi-arid areas, since soils are typically and scarcely vegetated. In this study, extension and magnitude of soil contaminations with toxic elements from abandoned Kettara mine, in Morocco, are assessed using geochemical analysis and geostatistics for mapping. Soils and mine wastes are sampled and analyzed for 41 chemical elements (Mo, Cu, Pb, Zn, Ag, Ni, Co, Mn, Fe, As, U, Au, Th, Sr, Cd, Sb, Bi, V, Ca, P, La, Cr, Mg, Ba, Ti, Al, Na, K, W, Zr, Ce, Sn, Y, Nb, Ta, Be, Sc, Li, S, Rb and Hf). Based on enrichment factor (EF), only five elements of interest (Cu, Pb, Zn, As, and Fe) were selected in this research. Geochemical background is determined with exploratory data analysis and geochemical maps were elaborated using geostatistics in Geographic Information System (GIS) environment. The obtained results show that Kettara soils are contaminated with metals and metalloid that exceed the established geochemical background values (Cu~43.8mg/kg, Pb~21.8mg/kg, Zn~102.6mg/kg, As~13.9mg/kg and Fe~56,978mg/kg). Geochemical maps show that the deposited mine wastes are responsible for soil contaminations with released metals and metalloid that have been dispersed downstream from the mine waste mainly, through water after rainfall. For sustainable development and environmental planning, the current study is expected to serve as a reference for politicians, managers, and decision makers to assess soil contaminations in abandoned mine sites in Morocco.
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    Electrical and seismic tomography used to image the structure of a tailings pond at the abandoned Kettara mine, Morocco
    (Springer, 2012-03) Lghoul, Meriem; Teixidó, Teresa; Peña, José Antonio; Hakkou, Rachid; Kchikach, Azzouz
    The Kettara site (Morocco) is an abandoned pyrrhotite ore mine in a semi-arid environment. The site contains more than 3 million tons of mine waste that were deposited on the surface without concern for environmental consequences. Tailings were stockpiled in a pond, in a dyke, and in piles over an area of approximately 16 ha and have generated acid mine drainage (AMD) for more than 29 years. Geophysical methods have been used at the Kettara mine site to determine the nature of the geological substrate of the tailings pond, the internal structure of the mine wastes, and to investigate the pollution zones associated with sulphide waste dumps. Electrical resistivity tomography (ERT) and seismic refraction data were acquired, processed, and interpreted; the results from ERT and seismic refraction were complementary. A topographical survey of the tailings disposal area was also undertaken to estimate the volume of wastes and quantify the AMD process. Two-dimensional inverse models were used to investigate the geophysical data and indicated alteration zones at depth. It was determined that the material could be classified into three categories: tailings, with low resistivity (5–15 Ω m) and low velocity (500–1,800 m/s); altered, black shales, with intermediate resistivity (20–60 Ω m) and velocity (2,000–3,500 m/s), and; materials with high resistivity and velocity (>60 Ω m and >4,000 m/s, respectively), including unaltered shales associated with quartzite seams. The low-resistivity zone generates AMD, which migrates downward through fractures and micro-fractures. The substrate is composed of broken and altered shale, which facilitates AMD infiltration.
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    Laboratory Evaluation of the Use of Alkaline Phosphate Wastes for the Control of Acidic Mine Drainage
    (2009-07) Hakkou, R; Benzaazoua, M; Bussière, B
    Pyrrhotite tailings at the abandoned Kettara mine site in Morocco are producing acid mine drainage (AMD). We investigated the use of alkaline phosphate waste (APW) rock from a nearby operating open-pit phosphate mine to control the AMD. The neutralizing potential of the APW, using the Paktunc method, was estimated between 500 and 680 kg CaCO3/t. In laboratory column tests, the addition of 15 wt% APW to the coarse Kettara tailings produced leachates with significantly lower acidities and metal concentrations than unamended controls. The high calcium concentration in the flushed solutions indicates that calcite was responsible for the neutralization. Dolomite dissolution seems to be negligible and fluorapatite was stable under the testing conditions. It was also observed that when the treated solution comes in contact with unweathered Kettara coarse tailings, the pH becomes acidic, although the metal concentrations remain low.
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    Etude géophysique et hydrogéologique du site minier abandonné de Kettara (région de Marrakech, Maroc): contribution au projet de réhabilitation
    (2012) Lghoul, M; Kchikach, A; Hakkou, R; Zouhri, L; Guérin, R
    Les rejets sulfurés de la mine abandonnée de Kettara, située à 30 km au Nord-Nord-Ouest de Marrakech, sont directement entreposés sur un substratum schisto-gréseux fracturé. D'une superficie d'environ 16 ha, ils constituent une réelle source de pollution pour l'écosystème local en particulier à cause du Drainage Minier Acide (DMA) vers les eaux de surface et de la nappe phréatique. Le projet de réhabilitation du site minier de Kettara prévoit dans l'un de ses axes de minimiser l'effet DMA par neutralisation à l'aide de dépôts stériles riches en carbonates issus de l'extraction des phosphates de la mine de Youssoufia voisine. Ces derniers seront utilisés à la fois comme amendement des rejets miniers acides et comme couverture évapo-transpirante (barrière capillaire). Notre étude a permis d'une part, de mieux appréhender la nature et la structure du parc à résidus et de son substratum et d'autre part, de caractériser l'impact de ces résidus sur la qualité des ressources en eau souterraine. Les résultats issus de cette étude vont contribuer à la réussite du projet de réhabilitation du site.