Dramatic Decrease of Fukushima Derived Radionuclides in the Northwest Pacific Ocean 2011-2012

By Jay T. Cullen

A schematic view of the formation and subduction of mode waters in the North Pacific

The purpose of this diary is to report on a recently published (Jan 2015) open-access, peer reviewed study which examined the activities of 137Cs (half life 30.2 yr), 134Cs (half life ~2.1 yr) and 90Sr (half life ~28.8 yr) in the northwest Pacific off the coasts of Japan and China. The diary is part of a ongoing effort to communicate the results of scientific research into the impact of the Fukushima Dai-ichi nuclear disaster on environmental and public health. Men and colleagues report on how activities of these fission produced isotopes changed between three research expeditions in June 2011, December 2011 and June 2012. Activities in seawater decreased dramatically through time for all three isotopes consistent with very high release rates measured from the Fukushima site in March-April 2011 followed by ongoing but many orders of magnitude (10,000 – 100,000 fold) lower releases from the site thereafter. By 2012 the impact of the Fukushima releases could be still be detected in most samples for Cs isotopes however 90Sr distributions were much more uniform with the highest measured activity only slightly above the pre-Fukushima background. These results are consistent with:

  1. the relatively small source term for 90Sr from compared with the Cs isotopes from Fukushima as determined by measurements of air, soil and water after the disaster
  2. the much lower Fukushima derived activities for these isotopes in the eastern Pacific off of North America being measured given decay and mixing of the contamination as it is transported by ocean currents

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Most Recent Measurements of Plutonium in Pacific: Fukushima Fallout Undetectable

By Jay T. Cullen

@JayTCullen and @FukushimaInFORM

The purpose of this post is to report results from two recently published studies on plutonium releases from Fukushima to the Pacific Ocean. The post contributes to an ongoing series where results from peer-reviewed studies on the impact of the triple meltdowns at the Fukushima Dai-ichii nuclear power plant on the health of the Pacific ecosystem and residents of the west coast of North America are reported. A frequently asked question of those involved in monitoring the health of the North Pacific is why more measurements of the long lived, alpha-emitting isotopes of plutonium (239Pu half-life 24,100 years; 240Pu 6,570 years) are not being made given the potential for these isotopes to pose radiological health risks. Previous work indicates that 239+240Pu releases from Fukushima were about 100,000 and 5,000,000 times lower than releases from the Chernobyl disaster in 1986 and 20th century weapons testing respectively. Initial measurements of Pu isotopes in seawater and marine sediments off the coast from Fukushima indicated no detectable change occurred in Pu inventories in the western Pacific after the disaster. These two most recent studies monitored the activity and isotopic composition of Pu in seawater and marine sediments off of Japan from 2008-2013. Similar to earlier work these studies find that the release of Pu isotopes by the Fukushima accident to the Pacific Ocean has been negligible. The Fukushima signal is not detectable in the ocean off Japan relative to legacy sources from atmospheric weapons testing in the 20th century. Given these accumulating results 239+240Pu from Fukushima is unlikely to negatively impact the health of the Pacific Ocean ecosystem and levels in the environment from Fukushima will not pose a danger to the population of North America.
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Prince Rupert Citizen Science Monitoring Continues for February 2015

Feb. 19, 2015

Prince Rupert BC

Prince Rupert’s third sample was recently collected by our volunteer team including students from NWCC Desiree Louis (College and Career Prep program) and Michael Standbridge (Applied Coastal Ecology (ACE) program). Sampling is being coordinated by Cheryl Paavola (Instructor and Science Lab Tech) at Northwest Community College – Prince Rupert.

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More Citizen Science Seawater Monitoring Results: No Fukushima Contamination Detected

By Jay T. Cullen

@JayTCullen and @FukushimaInFORM

February 16, 2015

What we found:

The absence of any detectable 134-Cs (an unambiguous fingerprint isotope of Fukushima contamination) in the seawater samples indicates that as of November 2014 these locations covering the length of the British Columbia coast have not be affected by ocean currents carrying Fukushima contamination.

The detection limit for 134-Cs averages ~0.2 Bq m-3

Newly added results come from seawater samples collected in collaboration with citizen scientists at the following locations in British Columbia, Canada during November 2014.

  1. Bamfield
  2. Masset, Haida Gwaii
  3. Lax Kw’alaams

Samples were processed and the amount of gamma emitting isotopes determined using a high purity germanium detector.  We look primarily for radioisotopes of cesium (134-Cs half life ~2 years and 137-Cs half life ~ 30 years) for the following reasons:

  1. 134-Cs has a half life that is short enough that all other human sources to the environment have decayed away making it an ideal tracer for Fukushima contamination
  2. next to the short lived Iodine-131 (half life ~ 8 days), Cs isotopes were released in greatest activity to the environment from Fukushima and would be most likely to represent a radiological health risk given their chemistry and propensity to be taken up by the biota
  3. other isotopes were released in much lower amounts from Fukushima relative to Cs (see other posts here and search for plutonium and strontium for example) and would therefore be much more difficult to detect
  4. because they are gamma emitters (unlike Pu isotopes and 90-Sr which emit alpha and beta radiation respectively) they are relatively easy and resource efficient to detect

The absence of detectable 134-Cs indicates that waters near these locations spanning the length of British Columbia have not been contaminated with Fukushima radioactive elements transported across the Pacific by prevailing currents as of Nov 2014. The presence of 137-Cs is due to historical sources of this human made isotope owing to atmospheric nuclear weapons tests in the 20th century and contamination from the Chernobyl disaster in 1986. You can read about the levels of 137-Cs in the North Pacific pre-Fukushima here.

More results will be published as they become available.

Talk at Mobilizing Science Knowledge and Research: A National Centre of Excellence Symposium

Originally posted on Cullen Lab: Chemical Oceanography:

Knowledge Mobilization Symposium Halifax 2015January 28, 2015

Cullen traveled to Halifax to present a talk about the early stages of the InFORM project and efforts to build a citizen scientist network and mobilize knowledge about the impacts of the Fukushima Dai-ichi disaster on the health of the North Pacific and residents of Canada’s west coast.

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Kelly Creek Community School Collects January 2015 Fukushima Monitoring Sample

Powell River, BC

Jan. 16, 2015

January sampling was carried out in close proximity to the Kelly Creek Community School on the Sunshine Coast of British Columbia.  According to volunteer citizen science coordinator Katherine McLean the school students helped to document the sampling and they saw two sea lions catching herring just off the beach.

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InFORM Citizen Science: Collecting January 2015 Seawater Sample at Salt Spring Island, BC

Jan. 15, 2015

Citizen scientist volunteer Karen Clemson collected seawater for the InFORM project on Vesuvius Beach, Salt Spring Island BC.

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Vesuvius Beach, Salt Spring Island BC Canada

Prince Rupert Citizen Science Monitoring in January 2015

Jan. 9, 2015

Prince Rupert BC

Collection team for January 2015 was Brittany Fenwick and Michael Standbridge, both students at NWCC.  Michael has just started in the Applied Coastal Ecology (ACE) program, and had only been in Prince Rupert for a week. Brittany is taking classes and also works/volunteers at the local fish hatchery. Sampling is being coordinated by Cheryl Paavola (Instructor and Science Lab Tech) at Northwest Community College – Prince Rupert.

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