Satellite measurements of ocean temperature (illustrated by color) and the direction of currents (white arrows) help show where radionuclides from Fukushima are transported. Large scale currents transport water westward across the Pacific. Circles indicate the locations where water samples were collected. White circles indicate that no cesium-134 was detected. Blue circles indicate locations were low levels of cesium-134 were detected. Small amounts of cesium-134 have been detected in a water sample taken Feb. 19, 2015, from a dock in Ucluelet, British Columbia. (Woods Hole Oceanographic Institution)
The purpose of this diary is to report that for the first time ocean borne contamination from Fukushima has been detected at the shoreline in British Columbia representing the first landfall in North America. Citizen scientists collected the sample on February 19, 2015 in the town of Ucluelet on the west coast of Vancouver Island Canada. The isotope Cesium-134 (134Cs half life ~2 years) is an unequivocal fingerprint of Fukushima derived contamination because all other sources of this man made isotope (principally the Chernobyl disaster in 1986) are far enough in the past that 134Cs has long since decayed to levels too low to detect today. The Ucluelet sample contained 134Cs at 1.4 Becquerel per cubic meter (Bq m-3) of seawater and 5.8 Bq m-3 of the longer lived 137Cs (half life ~30 years). These levels were expected given measurements made by monitoring programs offshore and modeling studies which predict the arrival time and activity of Fukushima radionuclides. These levels of 137Cs and 134Cs, are well below internationally established levels that might represent a danger to human or environmental health. The next number of months will be very important to track the ocean transport of the contamination as citizen scientists with Our Radioactive Ocean and the InFORM project continue to collect samples up and down the coast of North America.
The location of Ucluelet BC is shown on the following map:
The results for the Ucluelet sample are reported decay corrected to the date of sampling (February 19, 2015). A good check on the quality of the data is to decay correct to the date of peak Fukushima input to the coastal ocean off Japan which is roughly April 6, 2011. These decay corrected values for 137Cs and 134Cs are 6.4 and 5.2 Bq m-3 respectively. As we know that pre-Fukushima levels of 137Cs were about 1.2 Bq m-3 owing largely to atmospheric weapons testing fallout in the 20th century the Bq m-3 this shows the Fukushima 137Cs/134Cs input ratio was equal to 1 and is consistent with previous marine monitoring work.
Monitoring of seawater and marine biota contamination will continue with the help of citizen scientist volunteers in the coming months and years to determine the impact of the Fukushima disaster along the coast of North America. Those interested should consult the following monitoring programs:
- Our Radioactive Ocean
- Kelp Watch
I will post more results here as they become available.
Sat Apr 11, 2015 at 3:41 PM PT: Here is a useful FAQ by reporter Tracy Loew of the Statesman Journal about the levels of Fukushima derived radionuclides along the west coast of North America: