Synchrotron-based investigations of biogeochemical transformations of priority contaminants in soils at DOE sties July 18, 2006 Presented by Jeff Fitts Environmental Research & Technology Division

3,000 inactive waste sites; DOE EM (Environmental Management) FY06 appropriation $6.6 billion The Big Three: Hanford, WA; Oak Ridge, TN; Savannah River, SC DOE Environmental Management Sites

Research funding from ERSP within DOE Environmental Remediation Sciences Program mission is to advance our understanding of the fundamental biological, chemical, and physical processes that control contaminant behavior in the environment in ways that help solve DOE’s intractable problems in environmental remediation and stewardship. ERSP Field Research Center at ORNL S-3 disposal ponds U processing waste In-use Neutralized 1984 Paved 1988

Manipulate Uranium oxidation state to control U solubility Oxidized uranium, U(IV), is soluble and mobile Reduced Uranium, U(IV), is insoluble and immobile Soil Bacteria often control the redox state of soil Two remediation approaches Extract uranium from the ground Stabilize uranium in the ground Groundwater Flow Uranium Plume

1.High nitrate (~1000 ppm in Area 2) 2.Acidity 3.Heavy metals (Ni, Al…) FRC conditions present challenges to in-situ bioremediation strategies Will introduction of nickel resistance into indigenous microbial community have a positive effect on nitrate reducers and stimulate iron and sulfate reducers? Problematic conditions 1.Too high redox for stimulating sulfate and Fe reducers 2.Affects metal bioavailability, and thus, toxicity 3.Inhibit nitrate reducers Result

ERSP project overview S3 ponds at ORNL Goal: Immobilize uranium in contaminated sediments via microbial reduction and precipitation Problem: Active uranium reducers are inhibited by co-contaminants in complex waste streams (e.g., heavy metals) Major project objectives Demonstrate application of natural gene transfer to improve community function under increased levels of toxic metal stress (Dr. Daniel van der Lelie, BNL Biology Dept.) Demonstrate ability to enhance uranium immobilization in ORNL sediments by indigenous microorganisms that have adopted the toxic metal resistance marker (Fitts)

Project design schematic FRC soils Model organisms Isolated from FRC fluidized bed reactor Nickel stress 1. Community structure 2. Improved nitrate red. Total community Horizontal gene transfer (in vivo) – soil columns Ni resistance Strain construction (in vitro) 1. S and Fe reduction 2. Uranium reduction and precipitation mechanisms

What is really happening to the uranium? How stable is the uranium associated with the soil? Could it become a problem in the future?

Contaminant speciation in complex real-world systems Heterogeneous materials such as soils Low contaminant concentrations Single-crystal oxide/water interfaces Derive atomic-level picture Test predictive models Speciation on model soil particles Speciation on model soil particles Focus on predominant processes Molecular details of transient species Improve predictions of contaminant behavior and in pure bacterial cultures 1 2 3

1. Growth media 2. Common soil bacteria, Pseudomonas w/ and w/o gene for Ni resistance 3. As a function of Ni concentration Role of soil bacteria and their mechanisms of toxic metal resistance Pure culture 1. Monitor bacterial growth (UV-Vis) 2. Measure Ni uptake by bacteria 2-5  l sample X-ray transparent window

C=O Scanning Transmission X-ray Microscope imaging at the carbon K-edge Washed cells exposed to Ni for 2 hrs Rinsed cells are dried on microscope window Ni resistance mechanisms Carbonates not observed O K-edge will be sensitive to NiO formation 0.8  m 2.5  m Carbonate in organic matrix Pseudomonas DMY2::ncc-nre exposed to 2 mM NiCl 2 C=C carbonate Optical Density at 290eV Cluster image NSLS Beamline X1A

U(VI) reduction by Fe(II)-containing minerals C Green rust: Fe(II)-containing mineral Green rust after Rxn w/ U(VI)-containing aqueous solution

Remobilization potential of sequestered Uranium After initial rxn with Green rust Reduced U, sequestered as U(IV) After exposure to oxygen Mixture of U(VI) & U(IV) Aqueous U(VI) Bioavailable Uranium How stable is U(IV) that is associated with Fe-oxide? What is the role of aqueous Fe(II)?

Pseudomonas DMY2 tested in column studies Media + Formaldehyde Media + 1 mM NiCl2 Media no Nickel added Kill 2,6 - FRC community 3,7 - FRC community + Pseudomonas wild type 4,8 - FRC community + Pseudomonas pMol222 5,9 - FRC community + Pseudomonas::ncc-nre

Geochemical interrogation: S, Fe & U at time zero U oxidation state at M5 edge S speciation and redox state U-Fe correlation U distribution port B Typical soil Organic matter Area 2 FRC soil inorganic sulfate sulfate reduced organic S species Area 2 FRC soil U 6+ standard U 4+ standard NSLS beamlines X27A & X15B

Geochemistry of columns after 65 days Ni distribution in Column 2 No reduction of Uranium observed Small increase in sulfide relative to kill (oxidation during transfer may be problem) Fe(III) oxides still dominate Initial mobilization of Uranium Nickel breakthrough observed but significant adsorption occurs Soil indicators by x-ray absorption spectroscopy Column effluent indicators

Determine chemical state of untreated wastesDetermine chemical state of untreated wastes Assess and optimize treatment technologies and remediation strategiesAssess and optimize treatment technologies and remediation strategies Assess end-states to improve long-term performance predictionsAssess end-states to improve long-term performance predictions Conduct basic science research to seed future innovation in cleanup technologiesConduct basic science research to seed future innovation in cleanup technologies Summary: Applications of synchrotron-based studies in nuclear waste management

Acknowledgements NSLS Measurements Paul Northrup (BNL Environmental Sci. Dep.) – XAS & Microprobe Bjorg Larson, Sue Wirick (Stony Brook University) – STXM James Ablett (BNL NSLS) – Microprobe beamline X27A Oak Ridge FRC Dave Watson (ORNL) BNL Biology Department Niels van der Lelie David Moreels, Safiyh Taghavi, Craig Garafola BNL Environmental Sciences Dept. Garry Crosson