Fukushima Accident Raised Marine Radioactive Strontium Levels
June 12, 2013

Marine Levels Of Radioactive Strontium Spiked Following 2011 Fukushima Accident

redOrbit Staff & Wire Reports - Your Universe Online

New research suggests that the accident at the Fukushima nuclear power plant two years ago increased the amount of radioactive strontium on the east coast of Japan by as much as one-hundred times their normal levels.

Experts from the Institute for Environmental Science and Technology (ICTA) and the Department of Physics of the Universitat Autònoma de Barcelona (UAB) studied the spread of the radioactive element in the coastal waters during the three months following the March 2011 accident.

The samples they analyzed showed that the amount of the strontium-90 radioisotope (90Sr) was between 90 and 900 Tbq (terabecquerels). The highest concentrations of the isotope were located to the north of the Kuroshio current, which acts as a barrier preventing radioactive material from being carried to lower latitudes, they noted.

The study measured the concentrations of both 90Sr and another strontium radioisotope, 89Sr. The researchers analyzed water samples from the surface through 200 meters in depth in a region 30-to-600 kilometers off Japan´s eastern coast.

“The concentrations found were up to 85 Bq•m-3 (becquerels per cubic meter) for strontium 90 and 265 Bq•m-3 for strontium 89,” UAB officials explained in a statement. “These findings point to an increase of up to two orders of magnitude — a hundredfold — in concentrations of strontium-90 in the sea, with respect to the background values for this part of the Pacific before the Fukushima accident, which were 1.2 Bq•m-3.”

“The presence of strontium-89, with a half-life of only 50 days, was further proof of a recent release. The highest concentrations of radioactive strontium were found 130 kilometers from the coast, in the eddies that form at the meeting point between the Kuroshio and Oyashi ocean currents,” they added. “The levels of strontium-90 were compared with those of caesium-137, collected in the same survey. This allows researchers to estimate that between March and June 2011 the nuclear accident led to a release into the sea of between 90 and 900 Tbq of Sr-90.”

The June 2011 study was part of an oceanographic campaign led by Woods Hole Oceanographic Institution, and the ICTA and UAB researchers worked in collaboration with researchers from the University of Seville. The researchers believe that their work will help assess the possible effect of radionuclide releases into the marine environment following the Fukushima plant accident.

“Although on a global scale, the Fukushima Dai-ichi accident and the amounts released from March to June, 2011 meant a relatively small increase in this radioisotope in the oceans — less than 1% -  the impact on the area studied was very obvious, showing the need to continue monitoring it and assess its possible effects on coastal fauna,” explained former ICTA researcher Núria Casacuberta Arola, who now works with ETH-Zurich.

“Since June 2011 there have been further large discharges of strontium from Fukushima that have not been measured with precision,” added lead investigator Pere Masqué of UAB. “This does not necessarily mean that levels are now higher than two years ago: they could even be lower, as the isotope is diluted and dispersed over time. Whatever the case, however, more research is needed into the impact of radioactivity on the areas that were most affected.”