Coastal monitoring: Results from 26 samples, mostly collected in September and October, did not find any of the Fukushima fingerprint isotope, 134Cs (2 year half-life), in the coastal waters. Low levels of 137Cs (~30 year half-life) were present in all of the samples. Also, some of the new results were from June-August, filling in some gaps that are related to calibration of the new spectrometer. No 134Cs was detected in samples returned for that interval.
These latest samples mark one year since the beginning of InFORM monitoring efforts. While clear evidence of the 134Cs plume is detected offshore, we are also seeing a clear trend towards increasing 137Cs contamination in the coastal environment. Over the last year, the amount of 137Cs in the samples from coastal BC waters have increased by ~0.5 Bq m-3.
The lack of 134Cs detected in coastal waters is not altogether unexpected. We know that while 134Cs and 137Cs were released from Fukushima in a 1:1 ratio in 2011, it has also been almost 2.5 half-lives for 134Cs (half-life = ~2 years). This means that there is less than 25% of the original 134Cs released to the environment remaining. So while our observations have seen an increase of 0.5 Bq m-3 in 137Cs concentration, there has also likely been a 0.125 Bq m-3 increase of 134Cs in the samples as well (expected increase = 0.5 Bq m-3 x 0.25 amount remaining after 2 half-lives = 0.125 Bq m-3). This would be the maximum expected increase in 134Cs due to mathematical rounding. However, given the volume of seawater we process and counting time alloted for these samples the typical detection limit of our method is ~0.2 Bq m-3. Therefore, 134Cs is likely present in the samples, but at levels below detection.
These results would indicate that the leading edge of the Fukushima plume is now being detected at low levels in BC’s coastal waters more exposed to the open Pacific. The maximum allowable concentration of radiocesium in Canadian drinking water is 10,000 Bq m-3. The levels being detected in our citizen science samples are thousands of times lower and are not a risk to the health of the marine ecosystem or the public.
Biotic monitoring: InFORM partners at Health Canada report that they only have a few of the 160 salmon samples remaining to analyze. Results will be released within the next few weeks when they are validated.