The coastal average concentration of cesium-137 is now at 2.7 Bq per m3 according to data from samples collected in March and April 2017, which are now available. While nearly 300% of the pre-Fukushima levels, our observations remain extremely low when compared to the 10,000 Bq per m3 drinking water limit as set by Health Canada’s Radiation Protection Bureau.
Since early in our monitoring we have measured a distinction between samples collected from oceanic locations compared to those collected in more estuarine settings. As we have previously explained, there are physical explanations for this as it simply takes time for the plume waters to transit the distance into the Salish Sea.
In addition to the circulation explanation, we have wondered if there is also a connection between the salinity of the waters sampled and the activity of the cesium signal. The hypothesis is that fresh, riverine, waters which are free of Fukushima cesium may have diluted the arrival of the marine Fukushima signal. River water should be free of Fukushima radiation these days since any radionuclides that were atmospherically deposited on land in the weeks and months following the accident in 2011 should have already eroded and passed through the watershed. So it is rational that we might see a mixing line in our data where fresher, river influenced, samples have the lowest 137-Cs concentrations while saline, oceanic influenced samples would have the highest 137-Cs concentrations. Read the full August update ->
Extended testing of select 2016 salmon samples has identified the Fukushima-fingerprint isotope in one sample re-measured earlier this year. The maximum level of contamination observed in a sample (134Cs: 0.07 Bq kg-1, 137Cs: 0.51 Bq kg-1) is over 1,700 times lower than the Health Canada Action Level (1,000 Bq kg-1) and is not known to be a health risk for either humans or the environment. These results are an update to the 2016 results for salmon and shellfish.
Salmon samples for 2017 have begun arriving for preparation at the University of Ottawa and analyses on the gamma spectrometer at Health Canada across town. We hope to again have nearly 100 samples generously donated from hatcheries and the subsistence fishery of our many First Nations partners.
The peak concentrations of the Fukushima plume are now nearing North American coastal waters according to the data collected in February 2016 along Line P. The highest concentrations are no longer measured at Station Papa, as they have been since it was first detected in June 2013. Rather, measured activities at Station Papa are now indicating the back side of the highest concentrations. Peak sea surface concentrations, the total of Fukushima radiation and remains from nuclear weapons testing, measured 8.3 Becquerels per cubic meter (Bq m-3) at station P8. This concentration is over 1,000 times lower than the 10,000 Bq m-3 level of concern according to Health Canada. Station P8, located ~200 km west of Tofino or nearly 300 km from the mouth of the Strait of Juan de Fuca remains well off the continental shelf and we know from coastal samples collected at the end of 2016, discussed below, that this peak signal has not yet progressed to the coast. Read more ->
Interested in older samples? Check out our archive!