The purpose of this post is to report on new results coming out the crowd-funded Our Radioactive Ocean program headed up by Dr. Ken Buesseler of Woods Hole Oceanographic Institution. This post is part of an ongoing series dedicated to scientific inquiry into the impact of the triple meltdowns at Fukushima on the health of the North Pacific Ocean and residents of the west coast of North America. Measurements of the cesium radioisotopes 134-Cs (half life ~ 2 years) and 137-Cs (half life ~30 years) were made on samples collected on a transect between Monterey Bay CA and Dutch Harbor AK this summer. Because of its relatively short half life 14-Cs serves as an unequivocal tracer of Fukushima contamination in the environment. Fukushima derived 134-Cs was detected at offshore stations with a maximum activity of ~ 2 Bq/m^3 and total 137-Cs activities of ~7 Bq/m^3 of seawater. Measurements have yet to detect 134-Cs in nearshore waters sampled up and down the North American west coast. These activities of Cs are orders of magnitude below levels thought to pose a measurable risk to human health or marine life, according to international health agencies.
For a primer on radioactivity in the ocean and the units used to discuss radioactive elements in the environment please visit this post.
A press release from WHOI regarding these new results can be found here and details about sampling locations and activities of Cs detected are available here.
At a great majority of sites sampled along the coast and offshore the activity of 134-Cs is below detection limit (~legacy contamination resulting from atmospheric weapons testing in the 20th century. Similar to previous work by Dr. John Smith of the Department of Fisheries and Oceans Canada the presence of the contaminated plume of seawater owing to releases from Fukushima can be detected in offshore stations (150 – 1500 km) with levels of 134-Cs approaching 2 Bq/m^3 and total 137-Cs (bomb + Fukushima) of about ~7 Bq/m^3. These levels of 137-Cs are similar to levels in the North Pacific Ocean that were present in 1990 owing to the combined effects of Chernobyl and weapons testing fallout as shown in the figure below.
Activities of these isotopes were about 10 million fold higher in coastal waters near the Fukushima Dai-ichi nuclear power plant off Japan in the weeks following the beginning of the disaster in March and April 2011 when rates of release and seawater concentrations were at their peak. Current releases from the plant support seawater activities on the order of 10’s-100’s of Bq/m^3 within 2 km of the plant site. The highest activities associated with the most contaminated seawater from Fukushima are predicted to travel across the North Pacific with prevailing currents and arrive in North American waters between this year and next. These offshore activities of Fukushima derived 137-Cs of ~ 5 Bq/m^3 exceed predicted activities of ~3 Bq/m^3 suggesting that offshore activities are likely reaching near peak values. The measurements being made by the international scientific community will undoubtedly help to improve our understanding of mixing and transport in the oceans.
The activities of radiocesium being detected offshore are well below levels thought to represent significant radiological health risks to marine organisms or residents of the west coast of North America. To this point no 134-Cs from the contaminated plume approaching the coast has been detected in nearshore waters. Ongoing monitoring by programs like Our Radioactive Ocean and its partner program InFORM which are making measurements of contamination in seawater and marine organisms will be key to understanding impacts of the Fukushima on our environment.
The most recent results of Kelp Watch 2014 , a program dedicated to monitoring for the presence of Fukushima sourced radionuclides off our Pacific Coast, are reported in this post. This post is the latest contribution to a series dedicated to the dissemination of information about the impacts of the Fukushima Dai-ichi disaster on the North Pacific Ocean ecosystem and on North American public health. New results from the second sampling period (June to August 2014) of Kelp Watch 2014 were just released and can be found here. As with previously reported results here and here no radioactive isotopes from Fukushima were detected in kelp growing at sampling sites spread across the eastern Pacific coast. However, significant quantities of the short lived radioisotope 131-Iodine (half life ~8 days) continued to be found in Los Angeles County and San Diego in southern California. Rather than being transported across the Pacific these isotopes were likely released locally in waste water that carries significant 131-I because of its application in nuclear medicine to treat thyroid maladies. The absence of 134-Cs in kelp suggest that ocean transport of Fukushima contamination has yet to reach North American coastal water.
Samples were collected June to August of this year at various sampling locations along the coast with some kelp obtained from Chile and Tasmania (where little Fukushima impact is expected) to serve as reference locations.
Full results for the second sampling period can be found here along with details about the goals and approach of Kelp Watch 2014.
Because of its relatively short half life of ~2 years radioactive 134-Cs serves as a useful tracer of Fukushima impact as it was released in significant quantities, with many other isotopes, into the environment after the disaster in March 2011. All other legacy sources of the human produced isotope have occurred far enough in the past that any 134-Cs present in the environment faithfully reflects release from Fukushima. Similar to previous work by this program all samples of kelp collected from the Pacific by Kelp Watch 2014 in June to August of this year had no detectable (detection limit ~ 0.04 Bq/kg dry weight of kelp) levels of 134-Cs suggesting that isotopes from Fukushima are not significantly affecting radioisotope activities in these organisms to date.
The authors summarize findings about 134-Cs and its longer lived cousin 137-Cs (half life ~30 yr) as follows:
Cesium-137 was detected in all West Coast samples at very low levels. This isotope is still detectable in the marine environment due to above-ground nuclear weapons testing that took place mostly in the 1950s and 1960s. The very low limits set on the shorter-lived Cesium-134 mean that the Cs-137 cannot be directly tied to the Fukushima releases and is more likely due to these “legacy” sources.
Ongoing monitoring of seawater and marine organism activity concentrations of radioisotopes from Fukushima will help to determine the likely impacts on the ecosystem and public health along North America’s Pacific coast resulting from the disaster. As always, I will report new results as they are made available and we look forward to more work from this quality monitoring program.
The purpose of this post is to report measurements of radioactivity in fish caught off the west coast of Canada based on the work of InFORM team member Dr. Jing Chen. A collaborative effort between Health Canada, Department of Fisheries and Oceans Canada, and the University of Victoria was published in May 2014 in the peer-reviewed, open-access scientific journal Radiation Protection Dosimetry (link). The authors examined the activities of cesium radioisotopes (134-Cs half-life ~2 years and 137-Cs half-life ~30 years) that were released in large quantities due to the triple reactor meltdowns at Fukushima Dai-ichi Nuclear Power Plant in 2011 as well as a naturally occurring polonium isotope (210-Po) that can pose radiological health concerns for human consumers of marine fish. Samples of chum and coho salmon, halibut, sablefish and spiny dogfish were analyzed and none were found to contain detectable levels of Fukushima derived radionuclides. Radiation doses to human consumers were determined by assuming a conservative worst case scenario where Cs isotopes were present at detection limits of the measurement and found to be 18 times lower than doses attributable to the naturally occurring, alpha-emitter 210-Po. The authors conclude that the radiation dose from Fukushima derived isotopes present in fish caught in Canadian waters represent a very small fraction of the annual dose from exposure to natural background radiation. Based on these measurements, at present, Fukushima derived radionuclides in fish do not represent a significant radiological health risk to Canadians. Continue reading Looking For Fukushima Radionuclides in Fish Caught Off the West Coast of Canada→
If you are interested in helping the scientific community document the presence of sea star wasting syndrome please visit the following University of California Santa Cruz website. Another great resource to learn more about the outbreak can be found on Karyn Traphagen’swebsite that provides fine photos and information.
In addition to the citizen scientist sampling network that is under construction the other pillar of the InFORM project is the collection of samples in the open North Pacific and Arctic Oceans. The first samples for radionuclide analyses were collected by University of Victoria undergraduate student Kathryn Purdon on the first leg of the icebreaker CCGS Sir Wilfrid Laurier’s annual operations in Canada’s far North.
The goal of our sampling program was to obtain a detailed information about the location and intensity of the Fukushima contaminated plume of seawater by collecting seawater across the northeast Pacific from Victoria to Dutch Harbor, Alaska and up through the Bering Strait in the Chukchi Sea in the Arctic Ocean.
60 litres of seawater was collected for each sample and processed to concentrate radioactive elements for subsequent detection by gamma spectometry.