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

Minerals

John W. Dockrey²  Matthew B. J. Lindsay³  K. Ulrich Mayer²  Roger D. Beckie²  Kelsey L. I. Norlund¹  Lesley A. Warren¹ 

[1] School of Geography and Earth Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada; E-Mail:;Department of Earth, Ocean and Atmospheric Sciences, The University of British Columbia, 2207 Main Mall, Vancouver, BC V6T 1Z4, Canada; E-Mail:;Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada; E-Mail:

关键词: mine tailings;    neutral rock drainage;    biooxidation;    Fe- and S-oxidizing bacteria;    synchrotron;    EXAFS;   

DOI  :  10.3390/min4010170

来源: mdpi

【 摘 要 】

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.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.