The effects of extreme geochemical conditions on microbial community composition were investigated for two distinct sets of sediment samples collected near weathered mine tailings. One set (SCH) showed extraordinary geochemical characteristics: As (6.7-11.5%), Pb (1.5-2.1%), Zn (0.1-0.2%), and pH (3.1-3.5). The other set (SCL) had As (0.3-1.2%), Pb (0.02-0.22%), and Zn (0.01-0.02%) at pH 2.5-3.1. The bacterial communities in SCL were clearly different from those in SCH, suggesting that extreme geochemical conditions affected microbial community distribution even on a small spatial scale. The clones identified in SCL were closely related to acidophilic bacteria in the taxa Acidobacterium (18%), Acidomicrobineae (14%), and Leptospirillum (10%). Most clones in SCH were closely related to Methylobacterium (79%) and Ralstonia (19%), both well-known metal-resistant bacteria. Although total As was extremely high, over 95% was in the form of scorodite (FeAsO4·2H2O). Acid-extractable As was only ~118 and ~14mgkg-1 in SCH and SCL, respectively, below the level known to be toxic to bacteria. Meanwhile, acid-extractable Pb and Zn in SCH were above toxic concentrations. Because As was present in an oxidized, stable form, release of Pb and/or Zn (or a combination of toxic metals in the sediment) from the sediment likely accounts for the differences in microbial community structure. The results also suggest that care should be taken when investigating mine tailings, because large differences in chemical/biological properties can occur over small spatial scales.
Bibliographical noteFunding Information:
We thank Bhoopesh Mishra and Drew Latta for help during the EXAFS data collection and Karen Haugen for thoughtful editing of the manuscript. Research under the Subsurface Biogeochemical Research Program Scientific Focus Area at Argonne was supported by the Subsurface Biogeochemical Research Program, Office of Biological and Environmental Research, Office of Science (OS), U.S. Department of Energy (DOE) , under contract DE-AC02-06CH11357 , as was use of the Advanced Photon Source, a DOE-OS use facility operated by Argonne. MRCAT/EnviroCAT operations are supported by DOE and the member institutions. This work also was supported by Korea Institute of Science and Technology – Gangneung Institute (Grant no. 2Z04381 ) and Korea Ministry of Environment as The GAIA Project- 2013000540005 .
© 2015 Elsevier B.V.
All Science Journal Classification (ASJC) codes
- Environmental Engineering
- Environmental Chemistry
- Waste Management and Disposal
- Health, Toxicology and Mutagenesis