The transport of close-in fallout plutonium in the Northwest Pacific Ocean : Tracing the water mass movement using 240 Pu/ 239 Pu atom ratio

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1 The transport of close-in fallout plutonium in the Northwest Pacific Ocean : Tracing the water mass movement using 240 Pu/ 239 Pu atom ratio Sang-Han Lee 1, *, Gi-Hoon Hong 2, Moon-Sik Suk 2, Janine Gastaud 3, Jerome La Rosa 4, Chul-Soo Kim 5, Eric Wyse 6, Pavel P. Povinec 7 1 Korea Research Institute of Standards and Science, Daejeon , Rep. of Korea, 2 Korea Ocean Research and Development Institute, Seoul , Rep. of Korea, 3 International Atomic Energy Agency, Marine Environment Laboratory, Monaco 4 National Institute of Standards and Technology, Ionizing Radiation Division, Gaithersburg, Maryland, USA 5 International Atomic Energy Agency, Agency s Laboratories (Seibersdorf), Austria. 6 New Brunswick Laboratory Argonne, Illinois, USA 7 Comenius University, Faculty of Mathematics and Physics, Bratislava, Slovakia

2 222 Rn Nuclear weapons testing Continental origin (wind transport) 210 Pb 90 Sr, 137 Cs, 239,240 Pu, 241 Am 210 Po 14 C, 3 H 7 Be, 10 Be,... Cosmic rays Atmosphere 222 Rn Precipitation 226 Ra 232 Th 228 Ra 228 Ac 228 Th 228 Ra 228 Th Scavenging 210 Pb 210 Po with organic and 7 Be, inorganic 39,240 Pu, 241 Am 238 U 234 Th particulate matter (complexes and sorption) 234 U 230 Th 235 U 231 Pa Seawater Advection and convection 137 Cs, 99 Tc and 129 I 224 Ra 220 Rn Continental Shelf 220 Rn 232 Th 228 Ra Re-mineralization Sedimentation with marine snow Particle reactive radionuclides ( 7 Be, 10 Be, 210 Pb, Th, Pu, Am isotopes, etc.) 226 Ra 222 Rn 210 Pb 230 Th 226 Ra 222 Rn Sediment

3 Pu isotopes High toxicity and possible radiological effects; 238 Pu (t 1/2 =87.74 yr), 239 Pu (t 1/2 = yr), 240 Pu (t 1/2 = yr), 241 Pu (t 1/2 =14.4 yr), 240 Pu/ 239 Pu atom ratio Stratospheric fallout ( the early 1950s): > 0.30 Stratospheric fallout ( the mid-1950s): Nevada test site : Global fallout : 0.18 Geochemical and oceanographic tracers

4 Seawater and sediment sampling stations from the Northwest Pacific Ocean. SW+SED Seawater+Sediment SW Seawater St. 1 SW+SED St. 3 SW SED Sediment St. 9 SED St. 8 SW+SED SED TEQ6 TEQ12 SED St. 7 SW St. 6 SED Kawabe et al., 2003

5 Seawater and sediment sampling stations from the Northwest Pacific Ocean. Equatorial Counter Current Fig. 1 Seawater and sediment sampling stations from the Northwest Pacific Ocean.

6 Seawater and sediment sampling on board

7 Co-precipitation and sequential separation of plutonium (Am, Th and some U) in the seawater supernatant solution Acidified and Filtered Sea Water ( liters) acidification to ph = 2 + AMP supernatant solution + oxalic acid + NaOH to ph = 5-6 supernatant solution + tracer: 242 Pu + carriers: Sr, Cs (with Cs-134, Sr-85) + KMnO 4 + NaOH to ph = 9 + MnCl 2 AMP (Cs) precipitate Ca(Sr)C 2 O 4 precipitate MnO 2 xh 2 O (Pu) precipitate (discard) Pre-concentration steps for 90 Sr, 137 Cs and Pu

8 Analysis of plutonium isotopes in the seawater MnO 2 xh 2 O (Pu) precipitate 20 L supernatant solution, Mn II ph 6-7 1M HNO 3 solution Fe(III), Pu dissolution in HCl + NH 2 OH HCl + Fe(III) (50 mg);naoh to [HCl] < 1M heat: Fe(III) reduces to Fe(II) Pu(IV,V,VI) reduces to Pu(III) + NaNO 2 : Fe(II) oxidizes to Fe(III) Pu(III) oxidizes to Pu(IV) + NH 4 OH to ph 8-9, heat/flocculate + HCl to final ph 6-7 Fe(OH) 3 Pu(IV) precipitate dissolution in HCl, conversion to nitrate with HNO 3 10 L MnO 2 dissolution procedure for Pu

9 Analysis of plutonium isotopes in the seawater 1M HNO 3 containing Fe(III) and Pu 8M HNO 3 containing Fe(III) and Pu(IV) + hydrazinium, heat: Fe III Fe II Pu(IV,V,VI) Pu(III) + conc HNO 3 4M HNO 3 Fe(II) Fe(III), Pu(III) Pu(IV) + NaNO 2 : Pu(III) Pu(IV) + conc HNO 3 8M HNO 3 Pu(IV) Pu(NO 3 ) 2-6 AG 1-X8 (NO 3- ) anion exchange resin column 8M HNO 3 10M HCl 0.1M NH 4 I-9M HCl Am fraction Th fraction Pu fraction Pu, Th and Am separation using anion exchange resins

10 Pu separation and purification or extraction chromatography (TEVA)

11 Pu purification (specially for ICP-MS) Pu solution in 20ml of 1M HNO 3 10mg of Nd g of Mohr s salt (NH 4 ) 2 Fe 2+ (SO 4 ) 2.6H 2 O Pu* Pu (III) 0.5ml of 25% NaNO 2 Pu(III) Pu(IV), U UO ml of 38-40% of HF Centrifuge 15mim. at 3000rpm Solution: UO 2 2+, HF, Fe 3+, NO 2-1 st NdF 3 (Pu 4+ ) Dissolve NdF 3 in 5ml of (4MHNO mg H 3 BO 3 ) + 15ml of 0.1M HNO 3 2 nd Purification using the same NdF 3 procedure Solution: UO 2 2+, HF, Fe 3+, NO 2-2 nd NdF 3 (Pu 4+ ) TEVA column Dissolve NdF 3 in 5ml of (4MHNO mg of H 3 BO 3 ) + 5ml of 2M HNO 3 20ml of 3M HNO 3 20ml of 10M HCl 0.1M HF-0.1M HNO 3 Plutonium

12 Depth (m) Depth (m) Depth (m) Depth (m) Pu (mbq/l) Pu (mbq/l) Povinec, et al., 2003 (Deep Sea Research II) GEOSECS (1973) GX GX-224 GX-225 GX Knorr73 (1978) 4000 KH-80-2 (1980) KH-80-2 (1980) CY-11 IAEA 97 (1997) 3000 St. 6 St. 7 St. 8 IAEA 97 (1997) Stn IAEA 97 (1997) IAEA 97 (1997) 5000 Stn-3 Stn *DUMMY GEOSECS:GX KH-80-2:CY-11 IAEA97:Stn GEOSECS:GX-229 Knorr73:St IAEA 97:Stn Pu (mbq/l) Pu (mbq/l) GEOSECS (1973) GX GEOSECS (1973) GX-229 Knorr73 (1978) Knorr73 (1978) St. 2 St. 3 St Knorr73 (1978) Knorr73 (1978) St. 2 St. 3 St. 4 St. 6 St. 7 St. 8 St. 13 St. 14 KH-82-1 (1982) KH-82-1 (1982) CE-8 IAEA 97 (1997) IAEA 97 (1997) Stn-6 GEOSECS:GX-229 GEOSECS:GX-229 Lee, et al., 2005 (Marine Geology) GEOSECS:GX-229 GEOSECS:GX-229 Knorr73:St Knorr73:St Knorr73:St KH-82-1:CE IAEA 97:Stn-6

13 Northwest Pacific Ocean Northeast Atlantic Ocean (Lee et al., 2009)

14 Deep-water circulation at low latitudes in the western North Pacific (Kawabe et al., 2003) St. 1 St. 3 St. 9 St. 8 St. 7 St. 6 TEQ6 TEQ12 Lower Circumpolar Water (LCPW)

15 Vertical profile of 240 Pu/ 239 Pu atom East Sea/ Sea of Japan (Kim et al., 2004)

16 Evaluation of the relative contribution from the global fallout and the close-in fallout Pu( Global ) Pu( Local) ( R ( R 2 R) R1) (1 (1 3.60R 3.60R 1 2 ) ), From simple mixing model of Krey et al. (1976). where R = ( 240 Pu/ 239 Pu atom ratios of the mixture for the water column), R 1 = 0.18 ( 240 Pu/ 239 Pu atom ratio of global fallout), R 2 = 0.36 ( 240 Pu/ 239 Pu atom ratio of local fallout). R 1 (Pu activity %) G + R 2 (Pu activity %) C = 100%

17 Pacific Seawater (profile) Station Pu / 239 Pu atoms ratio Rg Rc Plutonium (%) Rg (global fallout) Rc(close -in fallout) St Pu / 239 Pu Atom ratio Plutonium (%) R (global fallout) R (close -in fallout) mean mean St. 3 St mean mean

18 240 Pu/ 239 Pu atom ratios in the bottom sediments of the NW Pacific Ocean (Kim et al., 2003) (Wang and Yamada., 2010) ( )

19 The atom ratios of 240 Pu/ 239 Pu with latitude in the surface sediment 0.32 West Caroline Basin (St. TEQ 6 & TEQ 12) 240 Pu/ 239 Pu atom ratio Latitude( o N) East Mariana Basin (St. 6 & St. 8) Northwest Pacific (St. 1 & St. 9) Global fallout (0.18)

20 West Caroline Basin Equatorial Counter Current: St. TEQ 12 (flowing East) North Equatorial Current: St. TEQ 6 (flowing West)

21 North Equatorial Current: St. TEQ 6 (flowing West) Equatorial Counter Current: St. TEQ 12 (flowing East) TEQ cruise (Korean TOGA program) at 137 o E Line West Caroline Basin

22 N. Equatorial Current Equatorial Counter Current

23 Kuroshio Current LCPW (Lower Circumpolar Water) N. Equatorial Current Equatorial Counter Current

24 Conclusion The atom ratios of 240 Pu/ 239 Pu in the seawater samples were increasing with depth and were higher than the global fallout ratio (0.18). The elevated 240 Pu/ 239 Pu atom ratios indicate that the close-in fallout plutonium isotopes originating from the Pacific Proving Grounds (PPGs) due to the U.S. tests are prevailing in the seawater in the NW Pacific Ocean. While the atom ratio of 240 Pu/ 239 Pu in the surface sediment collected near the PPGs (at St. 6, 7, 8, TEQ 6) was significantly higher than the global fallout ratio, St. 1 and TEQ 12 presented the global fallout. As a consequence, the water masses associated with the currents would play a key role in driving the distribution of Pu and in transporting Pu from the PPGs to the far eastern marginal sea in the NW Pacific Ocean.

25 Thank you for your attention!