Small amounts of radioactivity from the 2011 Fukushima Dai-ichi Nuclear Power Plant accident have been found on the shoreline in British Columbia, but scientists say it’s “well below internationally established levels of concern to humans and marine life”.
Woods Hole Oceanographic Institution (WHOI) scientists found the traces from samples collected at more than 60 sites along the US and Canadian west coast and Hawaii over the past 15 months. The first sample containing detectable radioactivity from Fukushima was found last November 100 miles off shore of northern California. However, no radiation had yet been found along any of the beaches or shorelines where the public has been sampling since 2013.
“Radioactivity can be dangerous, and we should be carefully monitoring the oceans after what is certainly the largest accidental release of radioactive contaminants to the oceans in history,” said Ken Buesseler, a marine chemist at WHOI who has been measuring levels of radioactivity in seawater samples from across the Pacific since 2011. “However, the levels we detected in Ucluelet, British Columbia, are extremely low.”
Scientists at WHOI are now analysing samples for two forms of radioactive cesium (Cs) -134 and -137. Cesium-137 remains after atmospheric nuclear weapons testing and, according to WHIO, is found in all the world’s oceans because of its relatively long, 30-year half-life, meaning it takes 30 years for one-half of the cesium-137 in a sample to decay. Cesium-134 has a two-year half-life.
The Ucluelet sample contained 1.4 Becquerels per cubic metre (Bq/m³) – the number of decay events per second per 260 gallons of water – of cesium-134, which WHOI says is a “telltale sign” of having come from Fukushima, and 5.8 Bq/m³ of cesium-137.
Scientists have had to rely on a crowd-funding and citizen-science initiative known as ‘Our Radioactive Ocean’ to collect samples because no US federal agency is responsible for monitoring radiation in coastal waters.
“We expect more of the sites will show detectable levels of cesium-134 in coming months, but ocean currents and exchange between offshore and coastal waters is quite complex,” added Mr Buesseler. “Predicting the spread of radiation becomes more complex the closer it gets to the coast and we need the public’s help to continue this sampling network.”
