Radionuclides in the ocean Ken Buesseler Department of Marine Chemistry and Geochemistry Woods Hole Oceanographic Institution Woods Hole, Massachusetts, USA Yokohama June 2011

- We live in a sea of radioactivity - Natural sources are larger than man-made sources - Danger is in the dose - one banana = 12 Bq 40 K - need to eat 20 million banana’s go get dose of radiation concern - We can measure less than 1 Bq - In the ocean (and human body) different radionuclides have different fate and toxicity Ken Buesseler WHOI Many sources of radioactivity 1 Bq = 1 Becquerel = one radioactive decay per second 1 PBq = peta-Becquerel = one million billion Bq = 1,000,000,000,000,000 Bq

Various Routes to the Ocean: Boundary Conditions Atmospheric deposition Atmospheric deposition １ Mid-March （ 5 〜 30 P Bq ） Direct discharge ２ After late-March (3 〜 15 P Bq) small source today Through river runoff ３ Through underground water flow Through underground water flow ４ small and continues small and continues? 80% Fukushima contamination in ocean There are still some uncertainties on “where” and “how much” of different radionuclides were released to the environment. P (peta) = 10 15

One year history of cesium-137 in ocean immediately off Fukushima Levels prior to March 11 At nuclear power plant Ocean Cs levels peak on April 6th - possible reproductive effects and mortality for marine biota Levels of concern for seafood Highest ocean levels post Chernobyl US drinking water limit - Fukushima NPP represents unprecedented release of radionuclides to the ocean - levels decreased rapidly, then leveled off - so reactors are still a source (through Sept.’12) - but levels now safe for marine biota & human exposure - what about seafood? one banana April 1 June 1 Aug 1 Oct 1 Dec 1 Feb Data from TEPCO

JCOPE2 model (Bq/L) Masamoto et al. JAMSTEC

JCOPE2 Tracer-Run (Bq/L) Kuroshio current important for rapid cesium transport May 2011 Aug Nov Mar 2012 Position of >10 Bq m -3

Cesium-137 today off Japan Fukushima Dai-ichi Nuclear Power Plant Seawater 15 TBq (TBq = Bq) Seafloor 94 TBq River water <<1 TBq/month River sediment 0.8 TBq/month Power plant >0.3 TBq/month Kanda et al TUMST

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 & fish Modeling/predictions of future accidents Japan is leading studies, but more work is needed than any one lab, or any one country can take on Confirmation by multiple international and independent labs will build public confidence in Japan (and increase scientific insights) Studies of fish are not enough- need long term studies of ocean, seafloor, rivers, etc. Easier to measure Cs than to determine health effects

Sponsors of today’s event Arigatou Gozaimasu!

What about fish off Japan- where are fish most contaminated? - highest off Fukushima Bottom dwelling fish only Data source- Japan Fisheries Buesseler, in review for Science

What types of fish are most contaminated? - bottom fish & freshwater fish - still high after 1 year - variability unpredictable - 18% of fish reported are above limit Data source- Japan Fisheries Buesseler, in review for Science Ken Buesseler WHOI

137 Cs radioactivity at “Unloading dock” inside the plant harbor Data source: TEPCO 137 Cs radioactivity at “Unloading dock” inside the plant harbor Data source: TEPCO 137 Cs radioactivity (Bq/L) Leak from the plant 137 Cs release in summer 2012 Harbor-water: 2.3 x 10 6 m 3 Exchange rate: 0.44 day -1 (6 ～ 19 April 2011) Average 137 Cs at “Unloading dock”: 9.9Bq L -1 (1 April ～ 30 September 2012) 137 Cs release in summer 2012 Harbor-water: 2.3 x 10 6 m 3 Exchange rate: 0.44 day -1 (6 ～ 19 April 2011) Average 137 Cs at “Unloading dock”: 9.9Bq L -1 (1 April ～ 30 September 2012) 10 GBq day TBq month day Bq L -1 Unloading dock Plant harbor

Water volume (m 3 ) Contaminated water underneath the reactor/turbine housings of Reactors 1-4 Calculated by JK based on data released by TEPCO 137 Cs inventory (PBq) Volume 137 Cs “Highly-contaminated” water under the plant Remaining 137 Cs 156 PBq (May 2011) 3 PBq (September 2012) Processed 137 Cs 220 PBq (June 2011 ～ September 2012) Diluted by groundwater inflow Remaining 137 Cs 156 PBq (May 2011) 3 PBq (September 2012) Processed 137 Cs 220 PBq (June 2011 ～ September 2012) Diluted by groundwater inflow Possible groundwater seepage from nearby seafloor??? Possible groundwater seepage from nearby seafloor???

1 Bq = 1 Becquerel = one radioactive decay per second 1 PBq = petaBecquerel = one million billion Bq = 1,000,000,000,000,000 Bq - We live in a sea of radioactivity - Natural sources are larger than man-made sources - Danger is in the dose - one banana = 10 Bq - need to eat 20 million banana’s go get dose of radiation concern - We can measure less than 1 Bq - In the ocean (and human body) different radionuclides have different fate and toxicity Ken Buesseler WHOI Radioactivity in the Oceans Oceanus, June 2012 Cesium-137 Three Mile Island Fukushima 8-45 PBq Chernobyl 85 PBq Global fallout 1960’s 400 PBq

Special Oceanus issue on – Fukushima and the ocean Goal is to bring content of our presentations and discussions to general audiences Hard/web copies early May 2013 In English and Japanese Coincides with 2nd Colloquium in Woods Hole Wed. Nov. 14th 16:00 Ito Hall U. Tokyo Public Event- panel w/ Q&A

Exploring the impacts of the Fukushima Dai-ichi Nuclear Power Plants on the Ocean goal: present a scientific review of what we know and don’t know about contaminants released at Fukushima, their fate in the ocean, and their potential to impact marine ecosystems and human health What are the lessons learned? Goal is to inform, not alarm

JCOPE2 Tracer-Run (Bq/L) Kurashio current important for cesium transport

? LNT? ?! ?

Summary of sources and fate of Fukushima Cs in the ocean Direct ocean discharge PBq Atmospheric fallout PBq Rapid offshore transport >99% Cs soluble groundwater ? Rivers vertical mixing sinking marine snow near bottom sediment flow seafloor burial ≈ 0.04 PBq? remineralization FNPP