Fukushima Cesium in Higher Levels Detected Offshore

Higher levels of Fukushima cesium have been detected offshore. As scientists continue to monitor the spread of radiation in the ocean from the Fukushima nuclear accident, they're reporting that there are an increased number of contamination sites.

Researchers started monitoring radiation in the Pacific just three months after the accident that started in March 2011. With the help of citizen scientists to gather samples, the researchers used sophisticated sensors to look for minute levels of ocean-borne radioactivity from Fukushima. In 2015, the scientists added more than 110 new samples in the Pacific.

"These new data are important for two reasons," said Ken Buesseler, one of the researchers, in a news release. "First, despite the fact that the levels of contamination off our shores remain well below government-established safety limits for human health or to marine life, the changing values underscore the need to more closely monitor contamination levels across the Pacific. Second, these long-lived radioisotopes will serve as markers for years to come for scientists studying ocean currents and mixing in coastal and offshore waters."

Almost any seawater sample from the Pacific will have traces of cesium-137, which is an isotope of cesium with a 30-year half-life. Some of this is left over still from nuclear weapons testing carried out in the 1950s and 1970s. The isotope cesium-134 is the "fingerprint" of Fukushima, but with a two-year half-life, it decays much more quickly than cesium-137. Scientists can actually calculate back traces of cesium-134 to figure out how much was actually released from Fukushima in 2011.

"Levels today off Japan are thousands of times lower than during the peak releases in 2011," said Buesseler. "That said, finding values that are still elevated off Fukushima confirms that there is continued release from the planet."

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