Impacts Of The Fukushima Nuclear Accident On The China Seas Evaluation Based On Anthropogenic Radionuclide 137Cs

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February 2013 Vol.58 No.4-5: 552558
doi: 10.1007/s11434-012-5426-2


Impacts of the Fukushima nuclear accident on the China Seas:
Evaluation based on anthropogenic radionuclide 137Cs
WU JunWen, ZHOU KuanBo & DAI MinHan*
State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361005, China
Received March 9, 2012; accepted July 10, 2012; published online September 27, 2012

In order to evaluate the impact of the Fukushima nuclear accident on the China Seas, seawater samples from the South China Sea
(SCS), the East China Sea (ECS) and the Yellow Sea (YS) were collected in April–June 2011, and their 137Cs activities were
measured using low-background -spectrometry. 137Cs activities in the study area ranged from 0.75±0.07 to 1.43±0.08 Bq m3
with an average of 1.12±0.08 Bq m3. 137Cs activities initially increased from the nearshore to the inner shelf, and subsequently
decreased from the inner shelf to the outer shelf. Vertical profiles showed higher 137Cs activities at the surface but lower activities
at depth in the ECS, suggesting atmospheric input of 137Cs. As such, the distribution pattern of 137Cs in the region was presumably
determined by a combination of atmospheric deposition and subsequent mixing between different water masses including the
coastal currents, the Yangtze River plume and the Taiwan Warm Currents. Based on the inventory of 93 Bq m2 and the atmospheric deposition flux of 137Cs in the ECS of 32.2 mBq m2 d1 (5.4–42.9 mBq m2 d1) which we estimated, we derived the residence time of 137Cs in the upper water column to be 66 d (45–95 d). We concluded that in terms of 137Cs, the ECS was less impacted by the Fukushima accident as compared to the Chernobyl accident. The released amount of 137Cs into the ECS from the
Fukushima accident was minute.
Fukushima nuclear accident, anthropogenic radionuclide, 137Cs, radioactive contamination, China Seas, atmospheric

Wu J W, Zhou K B, Dai M H. Impacts of the Fukushima nuclear accident on the China Seas: Evaluation based on anthropogenic radionuclide 137Cs. Chin
Sci Bull, 2013, 58: 552558, doi: 10.1007/s11434-012-5426-2

The Fukushima nuclear accident, which was associated with
a magnitude 9.0 earthquake and the subsequent tsunami
occurred on 11 March, 2011, and released a large amount of
artificial radioactive fission products, including 131I, 134Cs,
Cs, 239Pu and 240Pu from the nuclear reactors into the environment via immediate discharge into the ocean and rapid
dispersal into the atmosphere [1]. Using a regional ocean
circulation model, Tsumune et al. [2] estimate that a total of
3.5±0.7 PBq (1 PBq=1015 Bq) of 137Cs was directly discharged to the ocean from 26 March to 30 May, 2011.
Buesseler et al. [3] further assess the impacts of the accident
on the marine environment based on a field survey from 4
to 18 June, 2011, and reveal that the 137Cs activities and
inventories markedly increased in the ocean waters sur*Corresponding author (email:
© The Author(s) 2012. This article is published with open access at

rounding Fukushima. In addition to this direct release into
the ocean, the accident also dispersed about 15 PBq of 137Cs
to the atmosphere, dominated by a leak from 12 March to 6
April, 2011 [4]. These nuclides once discharged into the
atmosphere might have a global effect through fast atmospheric circulation. Indeed, 133Xe, a typical nuclear fission
product was observed on 16 March, 2011 at the US Pacific
Northwest National Laboratory (46.28°N, 119.28°E), which
is located more than 7000 km from Fukushima [5]. Meanwhile, elevated 131I, 134Cs and 137Cs activities in both air and
rainwater samples were detected from 24 March to 9 April,
2011 at Thessaloniki, Greece (40.63°N, 22.97°E) [6], which
is located more than 7500 km from Fukushima.
The China Seas are located in the Northwest Pacific
Ocean. It might have been difficult for the materials released immediately