Cesium, iodine and tritium in NW Pacific waters – a comparison of the Fukushima impact with global fallout

Abstract

Abstract. Radionuclide impact of the Fukushima Dai-ichi nuclear power plant accident on the distribution of radionuclides in seawater of the NW Pacific Ocean is compared with global fallout from atmospheric tests of nuclear weapons. Surface and water column samples collected during the Ka'imikai-o-Kanaloa (KOK) international expedition carried out in June 2011 were analyzed for 134Cs, 137Cs, 129I and 3H. The 137Cs, 129I and 3H levels in surface seawater offshore Fukushima varied between 0.002–3.5 Bq L−1, 0.01–0.8 μBq L−1, and 0.05–0.15 Bq L−1, respectively. At the sampling site about 40 km from the coast, where all three radionuclides were analyzed, the Fukushima impact on the levels of these three radionuclides represents an increase above the global fallout background by factors of about 1000, 50 and 3, respectively. The water column data indicate that the transport of Fukushima-derived radionuclides downward to the depth of 300 m has already occurred. The observed 137Cs levels in surface waters and in the water column are compared with predictions obtained from the ocean general circulation model, which indicates that the Kuroshio Current acts as a southern boundary for the transport of the radionuclides, which have been transported from the Fukushima coast eastward in the NW Pacific Ocean. The 137Cs inventory in the water column is estimated to be about 2.2 PBq, what can be regarded as a lower limit of the direct liquid discharges into the sea as the seawater sampling was carried out only in the area from 34 to 37° N, and from 142 to 147° E. About 4.6 GBq of 129I was deposited in the NW Pacific Ocean, and 2.4–7 GBq of 129I was directly discharged as liquid wastes into the sea offshore Fukushima. The total amount of 3H released and deposited over the NW Pacific Ocean was estimated to be 0.1–0.5 PBq. These estimations depend, however, on the evaluation of the total 137Cs activities released as liquid wastes directly into the sea, which should improve when more data are available. Due to a suitable residence time in the ocean, Fukushima-derived radionuclides will provide useful tracers for isotope oceanography studies on the transport of water masses during the next decades in the NW Pacific Ocean.

Fukushima-derived radioactivity measurements in Pacific salmon and soil samples collected in British Columbia, Canada

“…1,[7][8][9] As cesium has been previously shown to accumulate in tissues, additional monitoring campaigns have been initiated to investigate the contamination of various freshwater 5,6 and marine 7,[10][11][12][13][14][15] biota, as well as to develop 137 Cs bioaccumulation models in Pacific food-webs. 16 The primary purpose of many radionuclide monitoring campaigns is to describe the degree of contamination in the environment or to provide a dose estimate to the public within a specific region.…”

“…16 The primary purpose of many radionuclide monitoring campaigns is to describe the degree of contamination in the environment or to provide a dose estimate to the public within a specific region. The data from these campaigns may then be pooled together to provide global estimates for the total worldwide radionuclide contamination from all major nuclear events 8 or to provide detailed effective dose estimates for the global population. 17 Although none of the monitoring campaigns listed above measured total radiocesium ( 134 Cs + 137 Cs) activity concentrations near Health Canada's action levels for total radiocesium at 1000 Bq/kg 18 or effective doses near the dose limit set by the Canadian Nuclear Safety Commission (CNSC) at 1 mSv/year, 19 there are still concerns held by many in the general public regarding the safety of consuming Pacific seafood.…”

Recent results from the AMS/IBA laboratory at the Comenius University in Bratislava: preparation of targets and optimization of ion sources

“…The AMS technology has been widely used in environmental studies, both terrestrial and marine. Specific applications included tracing of long-lived radionuclides ( 10 Be, 14 C, 36 Cl, 129 I, U-isotopes, etc.) in climate change, atmospheric, hydrology, marine, geology and geophysics studies [2,10,[16][17][18][19].…”

“…Some of the cosmogenic radionuclides (e.g. 10 Be, 14 C, 26 Al, 36 Cl, 41 Ca, 53 Mn, etc.) have been widely applied in space research, e.g.…”

“…Except the most frequently studied 134 Cs and 137 Cs (gamma-ray emitters easily measured with HPGe detectors [31,32]), which have been important for delivery of postaccident radiation doses to the public and biota [33], there have been many other radionuclides released during the accident [30,[34][35][36], requiring our attention. This has been motivated first of all because of delivery of radiation doses to the public and biota by long-lived radionuclides (e.g.…”