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

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

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

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.)

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

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

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

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

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

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

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

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.

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.

Naturally-Occurring Radium Isotopes

Flow Chart - Ln•Resin Method 1 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)

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).

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

Water Samples: MnO2 ppt Seawater MnO2 Suspension MnO2 ppt supernatant Seawater, 100-400 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)

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.

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

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.