Speciation of uranium in contaminated ground water at Rifle, CO
description
Transcript of Speciation of uranium in contaminated ground water at Rifle, CO
![Page 1: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/1.jpg)
Speciation of uranium in contaminated ground water at Rifle, CO
by Nikki Peck
![Page 2: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/2.jpg)
The Problem 2/3 of DOE sites have uranium-
contaminated ground water Estimated 4x1012 L of contaminated ground
water Excavation of contaminated soil ineffective
Oak Ridge, TN
Rifle, CO
[U] ≤ 50 mg/L [U] ~ 0.17
mg/LMCL: 0.044 mg/LEPA limit: .03 mg/L
![Page 3: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/3.jpg)
Uranium contamination and speciation Speciation: chemical/physical form, oxidation
state, local molecular structure U(VI) very soluble, very toxic U(IV) orders of magnitude less soluble Attempt to sequester uranium from ground
water by reducing U(VI) into U(IV)
biogenic uraninite
500 nm
U(VI) + 2 e- U(IV)
![Page 4: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/4.jpg)
Bioremediation technique: acetate stimulation
CH3COO− + UO2++ + H2O + NH4
+ UO2(s) + H+ + HCO3
−
Inject: electron donor (acetate, ethanol)
Stimulate microbial growth in acetate plumeDevelop metal-reducing conditions
Groundwater flow
U(VI) U(IV)
![Page 5: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/5.jpg)
Microbial metal reduction Anaerobic bacteria like Geobacter use metallic
ions like we use oxygen Acetate acts as an electron donor, stimulating growth and inducing anoxia Microbes reduce electron acceptors like iron, sulfate and, of course, uranium!
![Page 6: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/6.jpg)
But the question is…
WHAT FORM OF URANIUM FORMS IN THE FIELD?
![Page 7: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/7.jpg)
UraniniteCH3COO− + UO2
++ + H2O + NH4+ = UO2(s) +
H+ + HCO3−
Uraninite: least soluble form of nonmetallic U Produced by metal-reducing bacteria in pure
culturesBUT…Is uraninite actually the product of bioreduction in the field?
FT(Х
(k)•
k3)
O U
UraniniteR
![Page 8: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/8.jpg)
Rifle, CO Site of a former uranium mill Excavated under UMTRA, but ground water
remains contaminated with 0.17 mg/L U
![Page 9: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/9.jpg)
Rifle, CO Many wells drilled into soil to allow access to
aquifer
![Page 10: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/10.jpg)
In situ columns Rifle U concentration is very low,
making spectroscopy challenging
Need a method of adding U to allow for spectroscopy on sediment samples
Solution: in situ sediment columns!
Concentrate U in field conditions
![Page 11: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/11.jpg)
In situ columns Effluent pump Influen
t PumpU(VI) ac solution
Reactor
RGW
![Page 12: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/12.jpg)
In situ columns
![Page 13: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/13.jpg)
In situ columns: well deployment
![Page 14: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/14.jpg)
XAS consists of X-ray Absorption Near Edge Spectroscopy (XANES) and Extended X-ray Absorption Fine Structure (EXAFS)
XAS: X-Ray Absorption Spectroscopy
EXAFS
XANES
![Page 15: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/15.jpg)
XANES: determining oxidation state U(VI) vs. U(IV) shifts edge by ~3 eV Fit linear combination of known U(VI) and
U(IV) XANES spectra to find percentage
7% U(VI)93% U(IV)
![Page 16: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/16.jpg)
EXAFS: P101 Sediments
![Page 17: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/17.jpg)
EXAFS: P102 Sediments
![Page 18: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/18.jpg)
EXAFS: P101 & P102
P101 EXAFS P102 EXAFS
![Page 19: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/19.jpg)
Not uraninite! Actual data vs. Uraninite
FT(Х
(k)•
k3)
Rifle well P102 sediment
O U
UraniniteR
![Page 20: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/20.jpg)
Not uraninite! Actual data vs. Uraninite
FT(Х
(k)•
k3)
Rifle well P102 sediment
O U
UraniniteR
![Page 21: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/21.jpg)
What does this tell us? Clearly, the product of bioremediation is not
uraninite
Models that apply to pure bacteria cultures do not hold for in situ results!
CH3COO− + UO2++ + H2O + NH4
+ = UO2(s) + H+ + HCO3
−
![Page 22: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/22.jpg)
What does this tell us? Clearly, the product of bioremediation is not
uraninite
Models that apply to pure bacteria cultures do not hold for in situ results!
CH3COO− + UO2++ + H2O + NH4
+ = UO2(s) + H+ + HCO3
−
![Page 23: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/23.jpg)
So what is it? Obtain greater resolution to identify local
structure more precisely
Understand speciation over time—does it change?
How stable is this reduced uranium?
![Page 24: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/24.jpg)
AcknowledgementsSpecial thanks to… Department of Energy SLAC SULI Program My mentor, John Bargar Fellow SULI members Patricia Fox and Jim Davis at the USGS Jose Cerrato from WUStL Sung-Woo Lee and Carolyn Sheehan from
OHSU Marc Michel and Mike Massey Many, many more!
![Page 25: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/25.jpg)
Questions?
![Page 26: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/26.jpg)
Questions?
![Page 27: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/27.jpg)
Questions?
![Page 28: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/28.jpg)
Questions?
![Page 29: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/29.jpg)
Questions?
![Page 30: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/30.jpg)
Questions?
![Page 31: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/31.jpg)
Questions?
![Page 32: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/32.jpg)
Questions?
![Page 33: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/33.jpg)
Questions?
![Page 34: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/34.jpg)
Questions?
![Page 35: Speciation of uranium in contaminated ground water at Rifle, CO](https://reader035.fdocuments.in/reader035/viewer/2022062218/5681649b550346895dd677cf/html5/thumbnails/35.jpg)
Questions?