Environmental Science and Pollution Research

, Volume 15, Issue 6, pp 481–491

Microbial community dynamics in uranium contaminated subsurface sediments under biostimulated conditions with high nitrate and nickel pressure

  • David Moreels
  • Garry Crosson
  • Craig Garafola
  • Denise Monteleone
  • Safiyh Taghavi
  • Jeffrey P. Fitts
  • Daniel van der Lelie
AREA 5.1 • MICROBIAL WASTE DISPOSAL • RESEARCH ARTICLE

DOI: 10.1007/s11356-008-0034-z

Cite this article as:
Moreels, D., Crosson, G., Garafola, C. et al. Environ Sci Pollut Res (2008) 15: 481. doi:10.1007/s11356-008-0034-z

Abstract

Background, aim, and scope

The subsurface at the Oak Ridge Field Research Center represents an extreme and diverse geochemical environment that places different stresses on the endogenous microbial communities, including low pH, elevated nitrate concentrations, and the occurrence of heavy metals and radionuclides, including hexavalent uranium [U(VI)]. The in situ immobilization of U(VI) in the aquifer can be achieved through microbial reduction to relatively insoluble U(IV). However, a high redox potential due to the presence of nitrate and the toxicity of heavy metals will impede this process. Our aim is to test biostimulation of the endogenous microbial communities to improve nitrate reduction and subsequent U(VI) reduction under conditions of elevated heavy metals.

Materials and methods

Column experiments were used to test the possibility of using biostimulation via the addition of ethanol as a carbon source to improve nitrate reduction in the presence of elevated aqueous nickel. We subsequently analyzed the composition of the microbial communities that became established and their potential for U(VI) reduction and its in situ immobilization.

Results

Phylogenetic analysis revealed that the microbial population changed from heavy metal sensitive members of the actinobacteria, α- and γ-proteobacteria to a community dominated by heavy metal resistant (nickel, cadmium, zinc, and cobalt resistant), nitrate reducing β- and γ-proteobacteria, and sulfate reducing Clostridiaceae. Coincidentally, synchrotron X-ray absorption spectroscopy analyses indicated that the resulting redox conditions favored U(VI) reduction transformation to insoluble U(IV) species associated with soil minerals and biomass.

Discussion

This study shows that the necessary genetic information to adapt to the implemented nickel stress resides in the endogenous microbial population present at the Oak Ridge FRC site, which changed from a community generally found under oligotrophic conditions to a community able to withstand the stress imposed by heavy metals, while efficiently reducing nitrate as electron donor. Once nitrate was reduced efficient reduction and in situ immobilization of uranium was observed.

Conclusions

This study provides evidence that stimulating the metabolism of the endogenous bacterial population at the Oak Ridge FRC site by adding ethanol, a suitable carbon source, results in efficient nitrate reduction under conditions of elevated nickel, and a decrease of the redox potential such that sulfate and iron reducing bacteria are able to thrive and create conditions favorable for the reduction and in situ immobilization of uranium. Since we have found that the remediation potential resides within the endogenous microbial community, we believe it will be feasible to conduct field tests.

Recommendations and perspectives

Biostimulation of endogenous bacteria provides an efficient tool for the successful in situ remediation of mixed-waste sites, particularly those co-contaminated with heavy metals, nitrate and radionuclides, as found in the United States and other countries as environmental legacies of the nuclear age.

Keywords

BioremediationBiostimulationMicrobial ecologyNickel resistanceNitrate reductionSubsurface microbiologyUranium reduction

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • David Moreels
    • 1
  • Garry Crosson
    • 2
  • Craig Garafola
    • 1
  • Denise Monteleone
    • 1
  • Safiyh Taghavi
    • 1
  • Jeffrey P. Fitts
    • 2
  • Daniel van der Lelie
    • 1
  1. 1.Biology DepartmentBrookhaven National LaboratoryUptonUSA
  2. 2.Environmental Sciences DepartmentBrookhaven National LaboratoryUptonUSA