U.S. Department of Energy Office of Biological and Environmental Research

BER Research Highlights


Immobilization of Heavy Metals via Two Parallel Pathways During In Situ Bioremediation
Published: March 03, 2015
Posted: November 23, 2015

Bioreduction is being actively investigated as an effective strategy for subsurface remediation and long-term management of Department of Energy (DOE) sites contaminated by metals and radionuclides [i.e., uranium (VI)]. These strategies require manipulation of the subsurface, usually through injection of chemicals (e.g., electron donor), which mix at varying scales with the contaminant to stimulate metal-reducing bacteria. Evidence from DOE field experiments suggests that mixing limitations of substrates at all scales may affect biological growth and activity for U(VI) reduction.

To study the effects of mixing on U(VI) reduction, researchers used selenite, Se(IV), instead of U(VI) in the lab because Se(IV) is easier to handle and microbial reduction of Se(IV) and U(VI) is similar in that two immobilization pathways are involved. In one pathway, the soluble contaminant [Se(IV) or U(VI)] is biologically reduced to a solid [Se0 or U(IV)]. In the other pathway, sulfate, which is commonly present in groundwater, is first biologically reduced to sulfide; this product then abiotically reacts with the soluble contaminant [Se(IV) or U(VI)] to form a solid [selenium sulfide or U(IV)]. While the first pathway is well understood, the second pathway has not been widely studied. Another unique aspect of this study is that researchers investigated mixing and reaction in a microfluidic flow cell with realistic pore geometry and flow conditions that mimic the transverse-mixing dominated reaction zone along the margins of a selenite plume undergoing bioremediation due to injected electron donors in the presence of background sulfate. Microbial and chemical reaction products were characterized using advanced microscopic and spectroscopic methods. A continuum-scale reactive transport model also was developed to simulate this experiment.

Results demonstrate that engineering remediation of metal-contaminated sites via electron-donor addition can lead to secondary and abiotic reactions that can immobilize metals, in addition to previously studied biotic reactions. The improved understanding of selenite immobilization as well as the improved model can help in the design of in situ bioremediation processes for groundwater contaminated by selenite or other contaminants [e.g., U(IV)] that can be immobilized via similar pathways.

Reference: Tang, Y., C. J. Werth, R. A. Sanford, R. Singh, K. Michelson, M. Nobu, W. Liu, and A.J. Valocchi. 2015. “Immobilization of Selenite via Two Parallel Pathways During In Situ Bioremediation,” Environmental Science and Technology 49, 4543–50. DOI: 10.1021/es506107r. (Reference link)

Contact: Paul E. Bayer, SC-23.1, (301) 903-5324
Topic Areas:

  • Research Area: Subsurface Biogeochemical Research

Division: SC-23.1 Climate and Environmental Sciences Division, BER

 

BER supports basic research and scientific user facilities to advance DOE missions in energy and environment. More about BER

Recent Highlights

May 10, 2019
Quantifying Decision Uncertainty in Water Management via a Coupled Agent-Based Model
Considering risk perception can improve the representation of human decision-making processes in age [more...]

May 09, 2019
Projecting Global Urban Area Growth Through 2100 Based on Historical Time Series Data and Future Scenarios
Study provides country-specific urban area growth models and the first dataset on country-level urba [more...]

May 05, 2019
Calibrating Building Energy Demand Models to Refine Long-Term Energy Planning
A new, flexible calibration approach improved model accuracy in capturing year-to-year changes in bu [more...]

May 03, 2019
Calibration and Uncertainty Analysis of Demeter for Better Downscaling of Global Land Use and Land Cover Projections
Researchers improved the Demeter model’s performance by calibrating key parameters and establi [more...]

Apr 22, 2019
Representation of U.S. Warm Temperature Extremes in Global Climate Model Ensembles
Representation of warm temperature events varies considerably among global climate models, which has [more...]

List all highlights (possible long download time)