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O2, Fe(III) mineral phase and depth controls on Fe metabolism in acid mine drainage derived iron mounds

Burwick, John E

Abstract Details

2015, Master of Science, University of Akron, Geology.
The Mushroom Farm (MF), located in North Lima, Ohio, is an acid mine drainage (AMD)-impacted system that exhibits an Fe(III) (hydr)oxide iron mound derived from microbial activity. Bacterial activities in the iron mound facilitate dissolved Fe(II) oxidation and Fe(III) reduction, giving rise to subsurface geochemical and mineralogical gradients. The microbial transformation of metastable Fe(III) (hydr)oxide phases was observed in MF iron mound sediments, likely due to anaerobic microbial activities at depth. Dissolved oxygen (DO) diffusion limitations appear to control, at least in part, microbially-mediated Fe(II) oxidation and Fe(III) reduction in the MF iron mound. An Fe(III) reducing bacteria (FeRB) enrichment culture and capable of facultative anaerobic Fe(III) reduction or aerobic Fe(II) oxidation was isolated from the MF iron mound and incubated in media that allowed DO penetration and recreated the MF iron mound geochemical conditions. DO, Fe(II), pH and Fe(III) mineral phase depth profiles were used as proxies for microbial Fe(II) oxidation, Fe(III) reduction and Fe(III) phase transformations. DO availability exerted partial control over, and initially enhanced, Fe(II) oxidation in glucose-free incubations and Fe(III) reduction in glucose-amended incubations. Fe(II) oxidation rates suggest oxidation happened more rapidly in deeper media, potentially from DO accumulation and the resultant microaerobic conditions, which further facilitated microbial Fe(II) oxidation. Omission of the glucose electron donor appeared to trigger aerobic Fe(II) oxidation by the enrichment culture. Rates of Fe(II) oxidation further suggest that Fe(II) oxidation is not enhanced by the presence of goethite and was inhibited by schwertmannite. Goethite-amended incubations exhibited less bacterial Fe(III) reduction than the schwertmannite-amended, and the addition of goethite does not appear to facilitate Fe(II) oxidation or Fe(III) reduction. Fe(III) reduction in the schwertmannite-amended incubations occurred to a greater extent than in the other incubations, indicating schwertmannite is more bioreducible than goethite, due to its greater surface area and metastable crystal structure. Powdered X-ray Diffraction (XRD) analyses indicated there was some microbially-mediated mineralogical transformation from the amorphous Fe(III) phase (schwertmannite) to goethite, which was catalyzed by the presence of included and/or biogenic Fe(II), in the absence and presence of an organic carbon electron donor. The results of this work suggest microbially-mediated Fe cycling could be an important mechanism controlling vertical growth and lateral expansion of the iron mound.
John Senko, Dr. (Advisor)
Hazel Barton, Dr. (Committee Member)
Ira Sasowsky, Dr. (Committee Member)
58 p.

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Citations

  • Burwick, J. E. (2015). O2, Fe(III) mineral phase and depth controls on Fe metabolism in acid mine drainage derived iron mounds [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1436335313

    APA Style (7th edition)

  • Burwick, John. O2, Fe(III) mineral phase and depth controls on Fe metabolism in acid mine drainage derived iron mounds. 2015. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1436335313.

    MLA Style (8th edition)

  • Burwick, John. "O2, Fe(III) mineral phase and depth controls on Fe metabolism in acid mine drainage derived iron mounds." Master's thesis, University of Akron, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1436335313

    Chicago Manual of Style (17th edition)