2. Developments in Environmental Radiochemistry* Environmental Radioactivity Measurement Facility Department of Oceanography Florida State University Tallahassee, Florida USA * Research funded by the PG Research Foundation

3. Objectives  Study the distribution of U/Th decay- series nuclides to address problems in the earth/marine sciences.  Improve chemical and instrumental techniques for measurement of all radionuclides in the environment.

4. Current Projects  Tracing of groundwater discharge into the coastal zone via Rn-222, radium isotopes  Automated Rn-222 in water and improved Ra isotopes via Mn-fiber/Rn counting  Th-234 in marine sediments via extraction chromatography - LSC  Ra-228 via Diphonix – TRU  Resin

5. U-Series Disequilibrium in the Ocean R/V Eichrom

6. Th-234 in Marine Sediments: 234 Th Characteristics  Half-life = 24.1 d  Maximum beta energies: 198 keV (73%), 104 keV (27%)  Pa-234m energies: 2290 keV (98%), 1530 keV (2%) 238 U 4.5 x 10 9 y 234 Th 24.1 d 234 Pa 1.18 m 234 U 2.48 x 10 5 y

7. Th-234 in Marine Sediments: General Strategy  Add known amount Th-230 as yield tracer, leach sediment with HNO 3  Separate Th using TEVA  Resin  Count 234 Th/ 230 Th via LSC Options:(1) count resin directly (2) count TEVA elution (3) Cerenkov and/or LSC

8. TEVA  Resin: Acid Dependency  TEVA·Resin = Aliquot 336 (2:1 mixture, trioctyl: tridecyl methyl ammonium chlorides on nonionic polymeric support  Th(IV) has very high retention at 2- 3M HNO 3

9. Th-234 in Marine Sediments: Separation of Th/U via TEVA U and Th loaded onto standard TEVA column in 2.5M HNO 3 Rinse Load

10. Th-234 in Marine Sediments: Elution Curve total recovery (5 mL) ≥97% 1M H 3 PO 4 lowers Th retention on TEVA by several orders of magnitude; combines well with cocktail; lowers quench

11. Th-234 in Marine Sediments: Sample Preparation Hot Block 95 o C, 2 hrs. Hot Block 95 o C, 2 hrs. 230 Th tracer Hot Block 95 o C, 2 hrs Centrifuge, Rinse 1g Sediment HNO 3 /H 2 O 2 LSC plastic vial 2.5M HNO 3 1M H 3 PO 4 TEVA  Resin Counting: Cerenkov LSC discard Up to 36 samples may be processed simultaneously on the “Hot Block”

12. Th-234 in Marine Sediments: Results 8 sediment samples spiked with Th- 234 -- all produced values within 10% of expected value, most within 4%.

13. Laboratory-Scale MnO 2 ppt MnO 4 (purple) is reduced by added MnCl 2 to precipitate MnO 2 (brown). MnO 2 precipitate settles relatively quickly. Concentrates Am, Pu, Th, Ra…

14. Hold-Back of 90 Sr

15. MnO 2 ppt: Large Volume Seawater Samples Supernatant seawater transferred from one plastic tank to another via pumping — this will be used for 90 Sr and 137 Cs. MnO 2 suspension withdrawn from bottom of conical- shaped plastic tanks — processed for Am and Pu.

16. 238 U 4.49 x 10 9 y 226 Ra 1600 y 222 Rn 3.825 d 218 Po 3.05 m 214 Pb 26.8 m 214 Bi 19.7 m 214 Po 1.6x10 -4 s 210 Pb 22.3 y 232 Th 1.39 x 10 10 y 228 Ra 6.7 y 220 Rn 54.5 s 216 Po 0.158 s 212 Pb 10.6 h 212 Bi 60.5 m 212 Po 3.0 x 10 -7 s 208 Pb Stable 235 U 7.13 x 10 8 y 223 Ra 11.4 d 219 Rn 3.92 s 215 Po 1.83 x 10 -3 s 214 Pb 36.1 m 214 Bi 2.16 m 207 Pb Stable 208 Tl 3.1 m 207 Tl 4.79 m 4.78 5.49 6.00 5.68 6.08 6.78 6.28 7.698.78 6.62 6.28 7.37 6.81 6.55 5.71 5.60 Alpha Decay (MeV) Beta Decay 228 Th 1.9 y 228 Ac 6.13 h 224 Ra 3.64 d Radium Isotopes via Rn Analysis

17. MnO 2 -Fiber ( 226,228,224,223 Ra) Alpha Detector - - - 222 Rn 220 Rn 219 Rn 222 Rn, 220 Rn, 219 Rn 215 Po 216 Po 214 Po 218 Po Drierite Air Pump RAD7 Detection on Radon Monitor

18. TRU 1 2 1 2 Rinse 2M HCl 1 2 Diphonix 1 2 Load sample in 2M HCl Collect Ba-133 yield Hold >30 hrs. Process Actinide Elements Rinse 2M HNO 3 1 2 Load sample in 2M HNO 3 Elute 228 Ac with 4 M HCl Beta source preparation CeF 3 co-precipitation GFPC MnO 2 co-precipitation Dissolve in 2 M HCl Centrifuge Ra-228 via Diphonix-TRU

19. 228 Ac t 1/2 = 6.14 ± 0.13 hrs. Half-Life Determination ( 228 Ra sample)

20. Half-Life Determination ( 228 Ra + 90 Sr sample) 228 Ac t 1/2 = 6.10 ± 0.15 hrs.

21. Ra-228 Test Results Ra-228 + Sr-90 Ra-228 + Ra-226 Ra-228 Expected Ra-228