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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. DOE Environmental Management Sites. http://web.em.doe.gov/em94/sitesum.html.

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slide1

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

slide2

DOE Environmental Management Sites

http://web.em.doe.gov/em94/sitesum.html

  • 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
research funding from ersp within doe
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 1951-1983
  • Neutralized 1984
  • Paved 1988

http://www.lbl.gov/NABIR/

slide4

Two remediation approaches

  • Extract uranium from the ground
  • Stabilize uranium in the ground

Groundwater Flow

Uranium Plume

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
slide5

FRC conditions present challenges to in-situ bioremediation strategies

Problematic conditions

Result

  • Too high redox for stimulating sulfate and Fe reducers
  • Affects metal bioavailability, and thus, toxicity
  • Inhibit nitrate reducers
  • High nitrate (~1000 ppm in Area 2)
  • Acidity
  • Heavy metals (Ni, Al…)

Will introduction of nickel resistance into indigenous microbial community have a positive effect on nitrate reducers and stimulate iron and sulfate reducers?

slide6

ERSP project overview

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)

S3 ponds at ORNL

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)

slide7

Project design schematic

Nickel stress

1. Community structure

2. Improved nitrate red.

FRC soils

Total community

Horizontal gene transfer (in vivo) – soil columns

Model organisms

Ni resistance

mechanisms

Isolated from FRC fluidized bed reactor

Strain construction

(in vitro)

1. S and Fe reduction

2. Uranium reduction and precipitation

slide8

What is really happening to the uranium?

  • How stable is the uranium associated with the soil?
  • Could it become a problem in the future?
slide9

3

2

1

Contaminant speciation in complex real-world systems

  • Heterogeneous materials such as soils
  • Low contaminant concentrations

Speciation on model soil particles

and in pure bacterial cultures

  • Focus on predominant processes
  • Molecular details of transient species

Improve predictions of contaminant behavior

Single-crystal oxide/water interfaces

  • Derive atomic-level picture
  • Test predictive models
slide10

Role of soil bacteria and their mechanisms of toxic metal resistance

Pure culture

1. Growth media

2. Common soil bacteria, Pseudomonas

w/ and w/o gene for Ni resistance

3. As a function of Ni concentration

2-5 ml sample

1. Monitor bacterial growth (UV-Vis)

2. Measure Ni uptake by bacteria

X-ray transparent window

slide11

0.8mm

Optical Density at 290eV

Ni resistance mechanisms

2.5mm

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

carbonate

C=O

Pseudomonas DMY2::ncc-nre exposed to 2 mM NiCl2

Cluster image

Carbonates not observed

O K-edge will be sensitive to NiO formation

C=C

Carbonate in organic matrix

NSLS Beamline X1A

slide12

C

U(VI) reduction by Fe(II)-containing minerals

Green rust:

Fe(II)-containing mineral

Green rust after

Rxn w/ U(VI)-containing aqueous solution

slide13

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)?

slide14

Pseudomonas DMY2 tested in column studies

2,6 - FRC community

3,7 - FRC community + Pseudomonas wild type

4,8 - FRC community + Pseudomonas pMol222

5,9 - FRC community + Pseudomonas::ncc-nre

1

2

7

8

3

4

5

6

9

Kill

Media +

Formaldehyde

Media +

1 mM NiCl2

Media

no Nickel added

slide15

Geochemical interrogation: S, Fe & U at time zero

U-Fe correlation

U distribution

S speciation and redox state

port B

U oxidation state at M5 edge

Area 2 FRC soil

Area 2 FRC soil

U4+

standard

Typical soil

Organic matter

U6+

standard

inorganic sulfate

sulfate

reduced organic S species

NSLS beamlines X27A & X15B

slide16

Geochemistry of columns after 65 days

Column effluent indicators

Ni distribution in Column 2

  • Initial mobilization of Uranium
  • Nickel breakthrough observed but significant adsorption occurs

Soil indicators by x-ray absorption spectroscopy

  • Small increase in sulfide relative to kill
  • (oxidation during transfer may be problem)
  • Fe(III) oxides still dominate
  • No reduction of Uranium observed
slide17

Summary: Applications of synchrotron-based studies in nuclear waste management

  • Determine chemical state of untreated wastes
  • Assess and optimize treatment technologies and remediation strategies
  • Assess end-states to improve long-term performance predictions
  • Conduct basic science research to seed future innovation in cleanup technologies
slide18

Acknowledgements

BNL Environmental Sciences Dept.

Garry Crosson

BNL Biology Department

Niels van der Lelie

David Moreels, Safiyh Taghavi, Craig Garafola

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)

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