By Jay T. Cullen
The purpose of this post is to report analyses carried out by the InFORM project on muscle and blubber samples from a grey whale (Eschrichtius robustus), that beached near Tofino, BC on April 20, 2015. The post is the most recent in a series that aims to communicate results of scientific research into the impact of the Fukushima disaster on the environment. With the cooperation of the Ucluelet Aquarium the InFORM project was able to obtain samples of the whales muscle and blubber which were analyzed for the presence of gamma emitting radioisotopes in Health Canada’s laboratories in Ottawa, ON Canada. The gamma radiation spectra were dominated by naturally occurring radioisotopes, primarily Potassium-40 (40K half life 1.25 billion years), and after 24 hours of counting no Fukushima derived Cesium-134 (134Cs half life ~ 2 years), a fingerprint of the disaster in the environment could be detected. The unfortunate demise of the grey whale is very unlikely to have been the result of acute or chronic radiation exposure owing to Fukushima derived radionuclides in seawater and the whales food.
On April 20, 2015 a yearling grey whale was found washed up on Wickaninnish Beach near Tofino and Ucluelet British Columbia Canada.
Scientists working for Fisheries and Oceans Canada and Parks Canada started to dissect the body of a yearling grey whale on April 23 to perform a necropsy to determine why the whale died. The results of the necropsy are not yet available but there were some signs that the whale had been struck by a ship. The whale was 10 metres long and was making its second migration up to Alaskan waters when it died.
After the necropsy the whale was further dissected by the public and the skeleton was interred to allow remaining tissue to decompose. Two years from now the skeleton will be dug up and reassembled to be put on display at the Royal BC Museum in Victoria (a great museum to visit if you ever get the chance to come to Victoria).
We worked with Laura Griffith-Cochrane who is curator of the Ucluelet Aquarium to obtain tissue samples for radioisotope measurements. Some members of the public had wondered if Fukushima derived radionuclides might have contributed to the whales demise. Samples were frozen immediately and shipped to Health Canada’s Radiation Protection Bureau’s laboratories in Ottawa for analysis by gamma spectrometry. Results were as follows:
Many of the spectral features in both the whale blubber and muscle gamma spectra are attributed to emissions (gamma and x-ray photons) from the decay of naturally occurring radionuclides associated with the background radiation. These are principally 210Pb, 212Pb, 214Pb, and 214Bi, all of which originate form from the 238U decay series. In addition to this, we have strong gamma emissions at 511 KeV and 1460 KeV, due to annihilation events within the detector and naturally occurring 40K found in the sample, respectively. With regard to radiocesium, the principal gamma emissions characteristic of 134Cs would be found at 605 and 796 KeV, while for 137Cs, the principle gamma emission would occur at 662 KeV. There is no discernible gamma emission at these energies, relative to background, under the counting conditions employed (HPGe detector, 24 hour count).
It is very unlikely that exposure to man made isotopes contributed to the death of this young whale. The absence of Fukushima contamination suggests that accumulation from seawater and food for this individual was insignificant over the last two years. The levels of radionuclides in the whale are consistent with the low levels of Fukushima derived radionuclides measured in the northeast Pacific Ocean over the past four years.
As always I will continue to report new results as they are generated. We are measuring the alpha emitting isotopes in the samples and I will update this post with this information and the results of the whale necropsy when it is made public