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Comparison of Microbiological Populations of Mineral Heaps and Mine Wastes of Differing Ages in Active and Abandoned Copper Mines

Sulfide mineral-oxidising microorganisms play a fundamental role in global mineral cycles. Currently, the most common route for the exposure of sulfide minerals is as a result of extractive industries. However, there is a dearth of knowledge about the diversity of microbial populations of waste mineral heaps and biomining operations. Increased understanding of these populations, how they interact and the way in which they change over time has important implications for biomining, but also, crucially, in understanding the longevity of pollution genesis within mineral heaps. To this end, the microbial populations of heaps and mine wastes at three copper mines were investigated using biomolecular and classical techniques. The materials studied were: (i) an 11 year old biomining heap at the Bingham Canyon mine, Salt Lake City, U.S.A.; (ii) two mineral waste heaps deposited around 50 years ago at the São Domingos mine in southern Portugal; (iii) well-weathered mine spoil deposited at least 120 years ago at the Mynydd Parys mine, North Wales, U.K.. The Portuguese samples were found to be the most reactive, in terms of both acidity and concentrations of readily-extractable metals, while the Bingham Canyon heap was somewhat less so. T-RFLP, clone library and culture data implied that both of these sites were dominated by extremely acidophilic mineral-oxidising “Firmicutes”. The population of the São Domingos heaps was very simple, while that of the biomining heap was slightly more complex. In contrast, the spoil from Mynydd Parys was much more weathered, and thus less extreme. While extremely acidophilic mineral-oxidising Bacteria were isolated, the cultured mineral-oxidising population was dominated by moderately acidophilic, heterotrophic Gammaproteobacteria, though the total microbial population was dominated by uncultured Actinobacteria and unclassified Bacteria. The data imply that biodiversity may not be linked to heap age per se, but rather heap pH and possibly readily extractable metal concentrations. As sulfide minerals become depleted as heaps age, the microbial population becomes less dependent on mineral oxidation, and more ‘heterotrophically-inclined’. However, the potential for mineral-oxidation, and thus pollution genesis, remains. Advanced Materials Research Online: 2007-07-15 ISSN: 1662-8985, Vols. 20-21, pp 585-585 doi:10.4028/www.scientific.net/AMR.20-21.585 © 2007 Trans Tech Publications Ltd, Switzerland