Geomicrobiological characterization of Fe(II)- and Mn(II)-oxidizing activity at two mine drainage treatment sites
John M. Senko, Ph.D.
William Burgos and Ashley Davidson
We characterized geomicrobiological activities in two acid mine drainage treatment sites. A mine water discharge stream near Altoona, PA contains low pH (3.5) water with abundant soluble Fe(II) (2 mM), which remains at a high concentration over the course of the 29 m stream. Abundant Fe(III) crusts are evident in the stream, and oxygen concentration increases from approx. 5 ?M to approx. 135 ?M from the point of water emergence to the end of the stream. Fe(III) solids become less crystalline and less dense in regions as oxygen levels increase in the stream. Akaganeite and schwertmanninte predominate in the high-oxygen regions of the stream, while goethite is evident in the low-oxygen regions. Numbers of acidophilic, aerobic Fe(II)-oxidizing bacteria remain constant throughout the stream (approximately 6 x 104), suggesting that oxygen levels do not control numbers of Fe(II)-oxidizing bacteria, but may control the Fe(III) products formed by these organisms. Mn(II)-oxidizing activity was characterized in a limestone-based Mn removal bed located in Elk County, PA. Water (pH 5.2) emerges from an anoxic limestone drain and flows through a limestone bed where water pH increases to 6.5 at the end of the bed, with a corresponding decrease in soluble Mn(II) from 1.6 mM to less than 0.05 mM. Mn(II)-oxidizing bacteria comprise 20-44% of the total heterotrophic bacteria in the region of the bed where Mn(II) removal is occurring, suggesting that the prerequisite microorganisms for Mn(II) oxidation are present, and abundant in the Mn removal bed. Our results suggest that Fe(II)- or Mn(II)-oxidizing bacteria are present at acid mine drainage treatment sites whose activity may be exploited and stimulated for efficient removal of these metal contaminants.
John Senko received a B.S. in Biology from St. Vincent College in Latrobe,
PA, an M.S. in Biology from Duquesne University, Pittsburgh, PA studying
the enzymology of nitrate reduction in the iron-reducing bacterium Geobacter
metallireducens, and his Ph.D. from the University of Oklahoma, Norman,
OK studying anaerobic uranium reduction and oxidation with Lee Krumholz
and Joe Suflita. Currently, he's a post-doc with the Center for Environmental
Chemistry and Geochemistry at Penn State, working with Bill Burgos.