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Minerals 2014, 4(1), 170-190; doi:10.3390/min4010170
Article

Acidic Microenvironments in Waste Rock Characterized by Neutral Drainage: Bacteria–Mineral Interactions at Sulfide Surfaces

1,†
, 2
, 1,* , 1
, 3,‡
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 and 4
Received: 13 January 2014; in revised form: 4 March 2014 / Accepted: 17 March 2014 / Published: 21 March 2014
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Abstract: Microbial populations and microbe-mineral interactions were examined in waste rock characterized by neutral rock drainage (NRD). Samples of three primary sulfide-bearing waste rock types (i.e., marble-hornfels, intrusive, exoskarn) were collected from field-scale experiments at the Antamina Cu–Zn–Mo mine, Peru. Microbial communities within all samples were dominated by neutrophilic thiosulfate oxidizing bacteria. However, acidophilic iron and sulfur oxidizers were present within intrusive waste rock characterized by bulk circumneutral pH drainage. The extensive development of microbially colonized porous Fe(III) (oxy)hydroxide and Fe(III) (oxy)hydroxysulfate precipitates was observed at sulfide-mineral surfaces during examination by field emission-scanning electron microscopy-energy dispersive X-ray spectroscopy (FE-SEM-EDS). Linear combination fitting of bulk extended X-ray absorption fine structure (EXAFS) spectra for these precipitates indicated they were composed of schwertmannite [Fe8O8(OH)6–4.5(SO4)1–1.75], lepidocrocite [γ-FeO(OH)] and K-jarosite [KFe3(OH)6(SO4)2]. The presence of schwertmannite and K-jarosite is indicative of the development of localized acidic microenvironments at sulfide-mineral surfaces. Extensive bacterial colonization of this porous layer and pitting of underlying sulfide-mineral surfaces suggests that acidic microenvironments can play an important role in sulfide-mineral oxidation under bulk circumneutral pH conditions. These findings have important implications for water quality management in NRD settings.
Keywords: mine tailings; neutral rock drainage; biooxidation; Fe- and S-oxidizing bacteria; synchrotron; EXAFS mine tailings; neutral rock drainage; biooxidation; Fe- and S-oxidizing bacteria; synchrotron; EXAFS
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Dockrey, J.W.; Lindsay, M.B.J.; Mayer, K.U.; Beckie, R.D.; Norlund, K.L.I.; Warren, L.A.; Southam, G. Acidic Microenvironments in Waste Rock Characterized by Neutral Drainage: Bacteria–Mineral Interactions at Sulfide Surfaces. Minerals 2014, 4, 170-190.

AMA Style

Dockrey JW, Lindsay MBJ, Mayer KU, Beckie RD, Norlund KLI, Warren LA, Southam G. Acidic Microenvironments in Waste Rock Characterized by Neutral Drainage: Bacteria–Mineral Interactions at Sulfide Surfaces. Minerals. 2014; 4(1):170-190.

Chicago/Turabian Style

Dockrey, John W.; Lindsay, Matthew B.J.; Mayer, K. U.; Beckie, Roger D.; Norlund, Kelsey L.I.; Warren, Lesley A.; Southam, Gordon. 2014. "Acidic Microenvironments in Waste Rock Characterized by Neutral Drainage: Bacteria–Mineral Interactions at Sulfide Surfaces." Minerals 4, no. 1: 170-190.


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