![\"This](\"http:\/\/s2.twnmm.com\/thumb?src=\/\/s2.twnmm.com\/images\/en_ca\/12\/Fukushima-Radiation-Plume-WHOI-43195.jpg&w=690&h=388&scale=1&crop=1\")
This model of the Fukushima radiation plume in the Pacific was tested by the movement of the very plume itself, giving scientists a keen insight into how Pacific currents behave. Credit: WHOI\/YouTube<\/p>\n<\/div>\n\nMeteorologist, theweathernetwork.com<\/strong><\/div>\n
Wednesday, January 7, 2015, 8:09 PM – Radioactive isotopes originating from the Fukushima nuclear power plant in Japan have been slowly drifting across the Pacific Ocean since March 2011, and Canadian scientists have been using this to test some of their most basic ideas of how ocean currents work.<\/p>\n
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In March 2011, when the Fukushima Daiichi nuclear power plant was damaged by the magnitude 9.0 earthquake that struck off the east coast of Japan, it resulted in a ‘plume’ of radioactive cesium isotopes being released into the Pacific Ocean.<\/p>\n
While regions closest to the plant came under intense scrutiny, due to the health risk posed by these isotopes – cesium-134 (134Cs) and cesium-137 (137Cs) to be exact – scientists from the\u00a0Bedford Institute of Oceanography<\/a>\u00a0in Dartmouth, Nova Scotia began to closely monitor the plume as it was carried away by Pacific Ocean currents.<\/p>\n This wasn’t due to any risk to the ocean environment beyond Fukushima, though, or any radiation threat to the shorelines of North America (or any other part of the world). Even just months after the accident, ocean currents had so diffused the plume that radiation exposure levels had dropped to well below safety standards for drinking water, and by the time the plume had reached halfway across the ocean, the levels of radiation from the isotopes had dropped to such low levels that they would have been overwhelmed by the natural radioactivity of the ocean water itself.<\/p>\n The reason these scientists, led by Bedford research scientist John Smith, tracked these cesium isotopes was that they represented a unique opportunity to see Pacific Ocean currents at work, and verify the computer models they are currently using.<\/p>\n “We had a situation where the radioactive tracer was deposited at a very specific location off the coast of Japan at a very specific time,” Smith told\u00a0Phys.org<\/a>. “It was kind of like a dye experiment, and it is unambiguous – you either see the signal or you don’t, and when you see it you know exactly what you are measuring.”<\/p>\n One of the models being tested by these findings is shown below, from the\u00a0Woods Hole Oceanographic Institution<\/a>, in Woods Hole, Massachusetts.<\/p>\n Note that the scale on this model, in Bq per cubic metre, only goes up to 10,000 (the safe level in Canadian drinking water), and levels by September 2011 – even closest to the power plant – are well below that, at around 1,000 Bq per cubic metre. As the plume spreads out, levels drop to below 100 Bq\/m3, and the most concentrated areas represent only around 20-30 Bq\/m3 (the scale is\u00a0logarithmic<\/a>, so the greens halfway between 10 and 100 are in the low 20s). This is well below any danger level to humans or wildlife.<\/p>\n Ken Buesseler, a marine chemist at Woods Hole who is currently working with Smith, as well as University of Victoria researcher Jay Cullen, on a monitoring program\u00a0called\u00a0InFORM<\/a>, has been watching the waters along the northern coast of California for this same signal from Fukushima.<\/p>\n “We detected cesium-134, a contaminant from Fukushima, off the northern California coast. The levels are only detectable by sophisticated equipment able to discern minute quantities of radioactivity,” he said in\u00a0a Woods Hole press release<\/a>\u00a0back in November. “Most people don’t realize that there was already cesium in Pacific waters prior to Fukushima, but only the cesium-137 isotope. Cesium-137 undergoes radioactive decay with a 30-year half-life and was introduced to the environment during atmospheric weapons testing in the 1950s and ’60s. \u00a0Along with cesium-137, we detected cesium-134 \u2013 which also does not occur naturally in the environment and has a half-life of just two years. Therefore the only source of this cesium-134 in the Pacific today is from Fukushima.”<\/p>\n Smith and his team tested sites stretching out into the ocean up to 1,500 kilometres from the British Columbia coastline, gathering water samples and specifically looking for both cesium-134 and cesium-137.<\/p>\n
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DID YOU KNOW?<\/strong>\u00a0Radioactive elements, including uranium-238, tritium, potassium-40, carbon-14 and r<\/em>ubidium-87, which are naturally found mixed into seawater, give the ocean\u00a0an average natural radioactivity of 13,000\u00a0Becquerel (decays per second) per cubic metre<\/a>. The safe radioactivity level for drinking water, in Canada, is\u00a010,000\u00a0<\/a><\/em>Bq per cubic metre<\/a>. Even the human body gives off\u00a0roughly 100 Bq\/kilogram<\/a>.<\/em><\/p>\n
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