Since October, citizen scientists have been dipping buckets into the waters of B.C.’s coast, looking for fallout from the 2011 nuclear meltdown in Japan.
At the centre of the search are two man-made isotopes, Cesium-134 and Cesium-137, which act as “fingerprints” for radiation specific to the Japan disaster. Both isotopes were released when the reactors failed in the aftermath of an earthquake and tsunami, just as they were during nuclear testing in the mid-20th century.
While Cesium-137 has a half-life — the time it takes for the radioactivity to fall to half its original value — of 30 years, Cesium-134’s is only two years. That means that if Cesium-134 is found in a sample, scientists can be certain it came from Fukushima.
“It’s been sufficiently long since atmospheric weapons testing last century or the Chernobyl disaster that we don’t see traces of [Cesium-134 from those sources] anymore,” said University of Victoria ocean chemist Jay Cullen. “So if we detect it in seawater or an organism, then we know that sample has been affected by Fukushima.”
The radiation is as close as 100 kilometres, with levels expected to peak over the next two years. But so far, members of the InFORM Network — citizen scientists, and representatives from academia, government and non-governmental organizations — haven’t found anything in seawater samples collected by volunteers at 14 coastal locations.
“The models of ocean circulation that the physical oceanographers have put together suggest that we are going to see it along the coast and we can expect it to arrive over the next couple of years, the heart of that contaminated plume,” said Cullen, who leads the network.
InFORM is also monitoring marine life, which can absorb radiation. The first results, from sockeye salmon and steelhead trout selected for their known migration paths, showed traces of Cesium-137, but no Cesium-134.
The network will monitor samples over the next three years. But Cullen does not expect to find levels that pose acute health risks.
“It can pose a radiological health risk because it tends to concentrate in organisms,” Cullen said. “[But] health physicists suggest the exposure of consumers to these fish don’t pose a danger to anybody’s health.”
John Smith, a senior research scientist with Fisheries and Oceans Canada, agrees that the health risks are likely to be “extremely low.” At its peak, the radiation in the plume is expected to be three to five becquerels per cubic metre of water. Canadian guidelines for safe drinking water impose a limit of 10,000 becquerels per cubic metre, he said.
For Smith, who began monitoring the plume’s spread in 2011, it provides a “dye test” for testing theories about ocean currents. The results will have implications for all kinds of models, including understandings of climate change, he said.
“This was a unique oceanographic event in that a large quantity of radioactivity was deposited into the ocean off Japan at a given moment in time and at a given location. It was a tremendous disaster. But it has provided an oceanographic tracer for currents that has never occurred before.”
Smith’s research is focused along a line that stretches about 1,500 kilometres northwest from the Victoria area. Samples are collected three times a year at 26 locations.
In June 2011, no Cesium-134 had reached the line. By June 2012, it was identified at the westernmost station. By June 2013, it stretched along the line to the edge of the continental shelf. And by February 2014, the signal had increased.
“We expect to see the maximum in either 2015 or 2016. After that, it should begin to decline and return to present fallout levels,” Smith said.
Back on land, the InFORM Network remains an opportunity for volunteers to participate in scientific research, be they surfers or Scouts.
Lucas Harris, vice-chairman of Surfriders, said the project fits with the group’s environmental mandate. Members collect samples in Port Renfrew.
Bob Vangenne said collecting samples at Esquimalt Lagoon was a good challenge for his Scouts and Venturers groups. “This is a great opportunity to see what types of jobs are available, what research looks like and what needs to be done.”