Abstract
The mining industry is of major importance to Morocco’s economy. However, the abandoned pyritic mines are a source of potentially toxic elements that can cause the disruption of the surrounding ecosystems, constituting a huge threat to wellbeing and human health. The present study aimed to analyze the physical and chemical characteristics of different types of tailings and to investigate the microbial populations of acidophilic bacteria involved in the oxidation of pyrite. Coarse and fine tailings collected from different zones of the mine (dike and pond) at two different depths (oxidized and non-oxidized residues) were analyzed for their pH, electrical conductivity, total organic carbon, total nitrogen, available P, major elements, and pseudo-total metal concentrations. The abundance of acidophilic bacteria was determined, and some acidophilic bacterial strains were isolated and tested for their metal tolerance. Tailings showed a pH ≈ 2, very low nutritional content, and high concentrations of Cu, As, Zn, and Pb, which were higher in the non-oxidized samples. The microbial counts of iron- and sulfur-oxidizing bacteria were higher than heterotrophic bacteria, with the highest numbers detected in the oxidized fine tailings. The five acidophilic bacteria isolated from the tailings were affiliated to genera Alicyclobacillus and Sulfobacillus, commonly found in this kind of environment.
Highlights
IntroductionThe mining sector underpins the economic development of many countries [4]; intensive mining activity often leads to the disruption of natural ecosystems, causing high biodiversity losses [5,6,7]
The results obtained in this study clearly showed that the sulfide minerals in the Kettara tailings are oxidized by biological and chemical processes, explaining the acid mining drainage (AMD) in this area, which have been reported by several authors [8,10,21]
The physical, chemical, and microbiological parameters suggested the existence of chemical and biological processes responsible for the oxidation of sulfide minerals
Summary
The mining sector underpins the economic development of many countries [4]; intensive mining activity often leads to the disruption of natural ecosystems, causing high biodiversity losses [5,6,7]. Mining processes such as grinding, washing, and ore concentration, generate large amounts of waste rocks and tailings, which are heavily contaminated with metals dispersed into mine surrounding areas by wind and water erosion [8,9,10,11,12]. Mining wastes containing metal sulfide minerals, such as pyrite and pyrrhotite, are a global concern as they can suffer chemical and biological oxidation leading to acid mining drainage (AMD) [13,14].
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