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Ocean radiation levels returning to normal five years after Fukushima

Monday, 04 July 2016


Despite being the largest release of nuclear material into the world’s oceans, new research has shown that five years after the Fukushima accident radiation levels across the Pacific Ocean are rapidly returning to normal.

However, ongoing releases of radioactive material from the plant on Japan’s east coast continue to contaminate coastal waters around the plant.

There has also been a lack of support to continue monitoring oceanic radioactivity, which is still a cause for concern, according to the research authors.

The major international review was conducted by a team of scientists as part of the Scientific Committee on Oceanic Research and was co-authored by ECU Professor of Environmental Radiochemistry Pere Masqué.

The research examined radioactive caesium levels measured in the ocean from Japan’s coast right across the Pacific to North America.

Caesium is a by-product of nuclear power and is highly soluble in water making it ideal for measuring the release of radioactive material from the stricken Fukushima plant into the ocean.

Immediately following the earthquake in 2011 radiation levels off the coast of Japan were tens of millions of times higher than normal.

The review collected data from 20 studies of radioactivity associated with the Fukushima disaster. Professor Masqué said the analysis showed the levels were decreasing rapidly.

“Oceanic currents have dispersed the radioactive material across the Pacific Ocean as far away as North America,” he said.

“Radiation levels across the ocean are likely to return to levels associated with background nuclear weapon testing over the next four to five years.”

“As an example, in 2011 about of half fish samples in coastal waters off Fukushima contained unsafe levels of radioactive material however by 2015 that number had dropped to less than one per cent above the limit.”

“However, the seafloor and harbour near the Fukushima plant are still highly contaminated and monitoring of radioactivity levels and sea life in that area must continue.”

The review was presented at the Goldschmidt Geochemistry conference on July 1 and will be published in the Annual Review of Marine Science.

The research is available at the Annual Review of Marine Science webpage.

Article Reference: Buesseler, K.O., Dai, M., Aoyama, M., Benitez-Nelson, C., Charmasson, S., Higley, K., Maderich, V., Masque, P., Oughton, D. and Smith, J.N. (2016). Fukushima Daiichi-derived radionuclides in the Ocean: transport, fate, and impacts. Annual Review of Marine Science


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