Impacts of the Great East Japan Earthquake on the ocean environment

Transcription

1 Impacts of the Great East Japan Earthquake on the ocean environment Mitsuo Uematsu Atmosphere and Ocean Research Ins2tute, U of Tokyo, Japan Ken Buesseler Woods Hole Oceanographic Ins2tu2on, USA

2 MEMBERS: Mitsuo Uematsu (U Tokyo) Kimio HANAWA (Tohoku U) Atsushi TSUDA (U Tokyo) Motoyoshi IKEDA (Hokkaido U) Takashi ISHMARU (TUMST) Jota KANDA (TUMST) Michio KAWAMIYA (JAMSTEC) Yukio MASUMOTO (JAMSTEC) Yoshimi KAWAI (JAMSTEC) Masahiro SUZUMURA (AIST) Michio AOYAMA (MRI) Ken Buesseler Woods Hole Oceanographic InsNtuNon N. Fisher SUNY Stony Brook H. Dulaiova University of Hawaii J. Halverson Savannah River Lab T. Guilderson Lawrence Livermore NaNonal lab K. Higley Oregon State University H. Neis Int l Atomic Energy Agency Marine Lab I. Osvath Int l Atomic Energy Agency Marine Lab P. Masque University of Barcelona G. Henderson Oxford University

3 Cesium- 137 in the ocean- what do we know? - mostly from 1960 s weapons tes;ng but some local sources - soluble in seawater, 137 Cs half- life = 30 yrs 137 Cs (Bq m -3 ) Surface ocean 137 Cs ac;vi;es: 1990 Baltic Irish Sea Black Sea North Sea Arctic Mediterranean North Pacific Japan coast North Atlantic Indian Ocean South Pacific South Atlantic Antarctic IAEA 1995; Buesseler & Livingston, 1996, Yamada and Nagaya 1998

4 Long- term trend of 137 Cs in surface water in the western North Pacific Ocean: pre- Fukushima 137 Cs activity / Bq m Nuclear tests by former USSR, USA, etc. Nuclear tests by China Chernobyl Accident 137 Cs decrease due to decay Year Aoyama, M., Hirose, K., TheScien2ficWorldJOURNAL, 4, , 2004 and update

5 Sources of Fukushima radioacnve contaminants- air Airborne releases of radioac;ve contaminants due to overhea;ng, hydrogen explosions & fires Gases and vola;les dominate air releases 10 msv/hr Highest airborne releases on March 15 & 16

6 Sources of radioacnve contaminants - atmospheric deposinon - rain on March 15th provided most contamina;on on land % fell on ocean Yodhida and Kanda, 2012 Simulated atmospheric deposi;on of 137 Cs (Bq m - 2 ) by Masingar II of MRI Aoyama et al., 2013

7 Sources of radioacnve contaminants - direct discharge to the ocean Water used to cool reactors is a major release pathway for radioac;ve contaminants to the ocean However, leak from reactor in early April was likely the largest direct source of radioac;ve contaminants to the ocean

8 One year history of cesium- 137 in ocean immediately off Fukushima At nuclear power plant Ocean Cs levels peak on April 6th - possible reproduc;ve effects and mortality for marine biota - Fukushima NPP represents unprecedented release of radionuclides to the ocean Levels of concern for seafood - levels decreased rapidly, then leveled off one banana Levels prior to March 11 EPA drinking water limit Highest ocean levels post Chernobyl - so reactors are s;ll a source (through Sept. 12) - but levels now safe for marine biota & human exposure - what about seafood?

9 R/V Kaimikai- O- Kanaloa (U. Hawaii) at Osanbashi, Port Yokohama on 4 th June 2011

10 Aier the mee;ng with Ambasador Roos At the NSF Tokyo Branch, Embassy of the United States 31 st May 2011

11 Briefing with Japan and US scien;sts before the cruise At the NYK Mari;me Museum on 31 st May 2011

12 In April 2011, see both near shore and far field sources of cesium Fukushima! KEO! S1! JKEO! KNOT! 137 Cs! (Bq m -3 )! K2! 500! 400! 300! 200! 100! 0! Cs in ocean at low levels at great distances in April 2011 due to atmospheric source Higher Cs close to Japan due to direct ocean discharge Honda et al. 2012

13 SpaNal variability in Fukushima Cs determined by currents & mixing coastal eddy 134 Cs in ocean- June Cs t 1/2 = 2 yr >99.5% soluble 134 Cs varies by 3 orders of magnitude- up to 4000 Bq m - 3 Kuroshio acts as barrier (if air deposi;on to south, not very much) Highest values associated with near shore eddy Buesseler et al. PNAS April data available on line

14 Ocean currents transport cesium across Pacific Driiers were released off Japan in June 2011 Map shows surface ocean driier tracks as of July 2012 Provides direct measure of transport ;mes Rypina et al., 2012

15 Pacific surface ocean sampled using ships of opportunity みらい NYK AQUARIUS 凌風丸 Aoyama March 2011 to June 2012 白鳳丸 NYK Heijin

16 Example of 134 Cs in surface water for April- June 2011 Data sources: Aoyama et al.2012, Honda et al.2011, Kim et al.,2012 Inoue et al. 2011, Karasev 2012, MEXT monitoring Bq m - 3

17 Summary of Eastward transport of Cs across Pacific 137 Cs activity / Bq m Aoyama et al, 2012 AprJun2011 Julysept2011 OctDec2011 Janmar Longitude May Aug Nov Mar Eastward transport = 8 cm/sec (7 km/d) Cs decreases at source Posi;on of >10 Bq m - 3

18 Over Nme, Cs moves east and mixes deeper in ocean at 39N, 165E on 11 June 2012 stn RF Cs / Bq m Oct Depth / m Oxygen June 2012 maximum Sigma0=26.3 Station Year Month 10 6 Bq m -2 Bq m Cs inventory KS RF m Deeper than 200 m

19 EsNmates of total releases from Fukushima atmosphere ocean discharge Converging on totals Atmospheric fallout PBq Direct ocean discharge PBq

20 Summary budget of 137 Cs Global fallout as of ± 30 PBq a Es;mated N. Pacific pre- Fukushima 69 PBq b Fukushima direct discharge PBq c Fukushima atmospheric release PBq d Fukushima deposi;on on land PBq e Total Fukushima in ocean PBq Chernobyl global release in PBq f (only 10-20% of Chernobyl fallout in oceans = 9-17 PBq) a: Aoyama, M., Hirose, K., Igarashi, Y., J. ENVIRON. MONITOR., 8, , 2006 b: Aoyama unpublished data estimated 3-D distribution of 137 Cs c: Tsumune et al., 2011, Rypina et al., 2012, Charette et al., 2012 d: Chino et al., 2011, Morino et al, 2011, ISRN 2011, Aoyama et al. in prep. e: Aoyama et al. in prep. f: IAEA, Proceeding of an International Conference, Vienna, 8-12 Apr. 1996

21 Summary of sources and fate of Fukushima Cs in the ocean Direct ocean discharge PBq FNPP Rivers Atmospheric fallout PBq Rapid offshore transport >99% Cs soluble groundwater? sinking marine snow ver;cal mixing seafloor burial 0.04 PBq? remineraliza;on near booom sediment flow

22 Remember, its not just cesium isotopes that were released Tagami et al Gamma- ray spectra of soil from 20 km from FNPP

23 What about stronnum- 90? 137 Cs at NPP Even with clean up of Cs at NPP, 90 Sr remains elevated Dec leak 90 Sr at NPP 90 Sr 100 ;mes lower than 137 Cs in ini;al source Povinec et al. 2012

24 Conclusions Fukushima Cs isotopes widely distributed and diluted by ocean due to its soluble nature Peak releases early April but remaining 1,000 Bq m - 3 at NPP today Levels off shore decrease rapidly - horizontal transport fast & verncal mixing slow/seasonal SNll some uncertainty in total Cs sources from Fukushima - atmospheric PBq 137 Cs - direct ocean discharge PBq Seafloor sedimentanon is small, but important sink for Cs (Pu?) 131 I (fast decay)> 137 Cs= 134 Cs > x 90 Sr (new sources) >10 6 x Pu

25 Lessons learned Fukushima NPP represents unprecedented release of radionuclides to the ocean off Japan Many reasons for study- Human health- internal/external dose assessments Radioecology- marine biota New ocean tracers in Pacific Modeling/predicNons of future accidents Japan is leading studies, but more work is needed than any one lab, or any one country can take on ConfirmaNon by mulnple internanonal and independent labs will build public confidence in Japan (and increase sciennfic insights) Easier to measure Cs than to determine health effects

26 Fukushima Ocean Impacts Symposium: Exploring the impacts of the Fukushima Dai- ichi Nuclear Power Plant Accidents on the Ocean Sanjo Conference Hall, The University of Tokyo, Japan, 12 and 13 November 2012 Fukushima and the Ocean Public Colloquium, Ito Hall, The University of Tokyo, Japan, 14 Novmeber 2012 Fukushima and the Ocean Public Colloquium, Woods Hole, MA, USA, 9 May 2013 A special issue of OCEANUS both in English and Japanese will be published for public