1. Applications of Extraction Chromatography in Marine Geochemistry
Bill Burnett
Department of Oceanography
Florida State University

2. Acknowledgments
FSU: Mike Schultz, Reide Corbett, Peter Cable, Jaye Cable, Mike Lambert, Jamie Christoff, Guebuem Kim, Christine Andre
GEL: James Westmoreland, Richard Kinney, Barry Stewart
IAEA (MEL): Pavel Povinic, Jerry LaRosa
Eichrom: Mike Fern, Larry Jassin, Anil Thakkar, Michaela Langer
PG Research Foundation: Phil Horwitz

3. U-Series Disequilibrium in the Sea
222Rn
210Pb
222Rn
222Rn
238U ~ 3.2 g/L
230Th
226Ra
Seawater
Sediments
238U
234U
237
271
<1
~10
dpm/100L:
(231Pa, 210Pb, etc.)
~50

4. Example Applications
U-series (230Th/234U, etc.) dating of fossil corals: sea level, uplift studies, etc.
U-series dating of biogenic materials and sea-floor minerals: ages, growth rates & directions
Sediment accumulation rates (230Th, 210Pb, etc.)
Tracing groundwater flow into the ocean via natural Ra isotopes (226Ra, 228Ra, etc.)

5. Analytical Challenges for Environmental Samples
Complex and variable matrices, e.g., seawater, sediment, fish, Mn nodules, etc. — methods must be versatile
Very low abundance of certain nuclides — yields must be high
Many U/Th-series nuclides are characterized by similar alpha decay energies — separations must be complete

6. Eichrom Technologies, Inc.
Development of an idea at Eichrom Technologies, Inc...
Eichrom
Phil
Larry
Anil
Mike

7. PHIL... “Phil Has Ideas that Last”
“Bill…you need to use extraction chromatography to make your life easier”
Phil
Bill

8. Distribution of Ocean-Floor Phosphorites
fsu X X
RELICT
MODERN
UNDIFFERENTIATED X
AREA OF
UPWELLING
Glenn et al. Fig. 4

9. U-Series Dating Age (103 yrs) 231Pa/235U 230Th/234U 0.0 0.2 0.4 0.6
0.8
1.0 50
100
150
200
250
Age (103 yrs)
230Th/234U
231Pa/235U

10. “Phil, how can we do this separation…”
“Bill, when is FSU going to play a real football team?”
Phil
Bill

11. U/Th/Pa Method
1M HCl 5 1 / 2
2M HNO3
0.1M HCl - 0.1M HF 6 3
9M HCl 4
4M HCl
Recent results have shown that Pa may be effectively isolated from U and Th on TRU.Resin alone.
TRU .
Resin 1 - 4 ( d i s c a r d ) 6 T h
(~90-95%) 5 U / P a
Burnett and Yeh, 1995
cation exchange

12. Pa-231 Alpha Spectrum 80
231 Pa 60 40 20 4 5 6 7
Energy (MeV)
Pa-231 is determined via low-level alpha-particle spectrometry after separation by extraction chromatographic resins.

13. Groundwater Discharge into the Coastal Zone
224Ra
228Ra
224Ra, 228Ra, 226Ra, 222Rn
226Ra
224Ra, 228Ra
226Ra
Naturally-occurring radium isotopes are useful for tracing groundwater flow into the coastal ocean.

14. Naturally-Occurring Radium Isotopes

15. Flow Chart - Ln•Resin Method1 2
Load sample in 0.09M HNO3
Rinse 0.09M HNO3 3
0.35M HNO3 Ln •
Resin
0.5-2 L acidified sample
Ba-133
BaSO4 ppt
Conversion to BaCO3
{hold for ~30 hrs.}
0.09M HNO3
g-ray measurement Ba-133
228Ra via 228Ac
{proportional or HPGe counter}
226Ra via Rn emanation
223,224Ra via a-spectrometry
Ra concentrated by ppt with BaSO4. Ac separated from other radioactive species via Ln.Resin (Burnett et al., 1995)

16. Elution Curve — Ln•Resin
The Ac fraction is collected and a CeF3 precipitate prepared for low-level gas-flow proportional counting (Burnett et al., 1995).

17. The “Double-Pass” Approach
First Pass: 1
Second Pass: 1 2 2
Load sample in 2M HCl
Actinide 1
Actinide 1
Load sample in 2M HCl
Rinse 2M HCl 2 2
Rinse 2M HCl • •
Process Actinide Elements
Resin #2
Resin #1 1 2 1 2
226Ra via Rn emanation
Collect
Ba-133 yield
Hold >30 hrs.
223,224Ra via
-spectrometry
Extrude resin into plastic vial; add cocktail, count via LSC
2nd column options: TRU.Resin — load 2.5M HNO3; elute Ac 1M HCl, ppt CeF3, count
Diphonix — load 2M HCl; elute Ac 0.5M HEDPA, evap., count

18. Water Samples: MnO2 ppt Seawater MnO2 Suspension MnO2 ppt supernatant
Seawater, liters
Acidify to pH 2, add Pu/Am tracers, stir/hold
For 100L sample, add 35 mL sat KMnO4 (~2.1g); Pu-->Pu(VI), org oxid, purple color
Adjust pH to 8-9 with NaOH
Add 0.5M MnCl2 (2x vol of KMnO4); --> MnO2 ppt, dark brown
Seawater
MnO2
Suspension
2MnO4- + 3Mn2+ + 2H2O = 5MnO2 + 4H+
Re-adjust pH to 8-9 as necessary
Stir occasionally to keep MnO2 suspended for few hours
Allow Mn02(Pu, Am) ppt to settle overnight
Pump supernatant into clean tank for Cs, Sr processing
Drain MnO2 slurry from bottom tap
centrifuge/
filter
MnO2 ppt
(Pu, Am, Ra, Ba)
supernatant
Cs, Sr,...
(Povinic et al., 2000)

19. Large Volume Seawater Samples
Supernatant seawater transferred from one plastic tank to another via pumping — this will be used for 90Sr and 137Cs.
MnO2 suspension withdrawn from bottom of conical-shaped plastic tanks — processed for Am and Pu.

20. Smaller-Scale MnO2 ppt
MnO4 (purple) is reduced by added MnCl2 to precipitate MnO2 (brown). MnO2 precipitate settles relatively quickly.

21. Summary
U/Th decay-series disequilibrium in nature may be exploited to measure environmental processes
Known source and fixed rate of decay provides information stable elements cannot provide
Extraction chromatographic methods have greatly simplified processing of environmental samples.