Pushing the Limit: Fukushima Fingerprint Isotope Found in Salmon from 2015

Complete results from 2015 biotic monitoring. New results are larger icons with bold/italic labels.

For the first time, the Fukushima fingerprint isotope, cesium-134 (¹³⁴Cs; half-life ~ 2 years), has been detected at an extremely low level in a Canadian salmon by the InFORM project. The single sockeye salmon that tested positive was sampled from Okanagan Lake in the summer of 2015, according to scientists from the Radiation Protection Bureau at Health Canada, in cooperation with Fisheries and Oceans Canada and local First Nations.  The sample was one of a few (7 out of 156 total) individual fish that had trace levels of the longer lived  cesium-137 (¹³⁷Cs) (30 yr half-life) that we reported on last winter. To determine if this trace ¹³⁷Cs was from Fukushima or remnant from atmospheric weapons testing, InFORM reexamined these individual fish samples to see if extremely low levels of ¹³⁴Cs may be present. The results of this extended analysis show that trace (0.07 Bq kg^-1) levels of ¹³⁴Cs were detected in one sample from Okanagan/Columbia River population. No ¹³⁴Cs was detectable in the other samples. The observed levels remain well below the action level (1000 Bq kg^-1) set by Health Canada guidelines. 

As we reported in the winter 2016 update, 7 individual fish (out of the 156 measured) from 2015 tested positive for low levels (<1 Bq kg^-1) of cesium-137 (¹³⁷Cs). With its ~30 year half-life, ¹³⁷Cs is still present in the environment from 20th century atmospheric weapons testing and Chernobyl in addition to the Fukushima accident.  In contrast, no individual fish from the 2014 monitoring effort were found to contain detectable levels of ¹³⁷Cs. This difference led the team at the Radiation Protection Bureau to conduct a more detailed investigation of some of those few positive samples to determine if ¹³⁴Cs, the Fukushima fingerprint isotope, was present. Results from 5 of those 7 are now available and discussed below. The remaining two samples are still in processing.

To read more: https://fukushimainform.ca/2016/11/15/pushing-the-limit-fukushima-fingerprint-isotope-found-in-salmon-from-2015/

November 19, 2016 - Posted by dunrenard | Fukushima 2016 | Canada, Fukushima Radiation, Salmon