Update: Sampling for Fukushima Derived Radionuclides in the Northeast Pacific and Arctic 2015

By Jay T. Cullen

Locations where surface seawater samples were collected for the InFORM project in July 2015. Surface seawater temperatures at the time of collection are shown with values greater than 16C in the anomalous region referred to colloquially as “the blob”.

The purpose of this short post is to update readers on the activities of the Integrated Fukushima Ocean Radionuclide Monitoring (InFORM) project. This post is the most recent in a series documenting scientific research into the impact of the Fukushima Dai-ichi disaster on environmental and public health. Surface seawater samples were collected from the icebreaker CCGS Sir Wilfrid Laurier as it traveled between Victoria BC to Dutch Harbor Alaska during July 2015. These seawater samples will be analyzed to characterize the distribution of Fukushima derived radionuclides 137-Cesium (137Cs half life ~30 years), and 134-Cesium (134Cs half life ~2 years). As in previous years this information will help to determine how well model predictions of the activities and progression of ocean borne contamination across the Pacific Ocean match with observations. Understanding the spread of this contamination provides important information on the impact of the Fukushima Dai-ichi disaster on the health of the Pacific ecosystem and the North American public. The evolution of the contaminant plume in time and space also helps the scientific community to better understand ocean mixing which is a key parameter toward understanding the oceans role in mitigating atmospheric greenhouse gas increases and climate change.

60 liter seawater samples were collected and processed at sea by research assistant Laura McKay who is working with our group at the University of Victoria this summer. The picture below shows Laura in the main scientific laboratory on the icebreaker next to her filtration/concentration setup.

McKay and the KNiFCN resin preconcentration system on the CCGS Sir Wilfrid Laurier.
We look primarily for radioisotopes of cesium (134Cs half life ~2 years and 137Cs half life ~ 30 years) for the following reasons:
  1. 134Cs 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 diaries I’ve written 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 90Sr which emit alpha and beta radiation respectively) they are relatively easy and resource efficient to detect

Samples were collected at the following locations to help characterize the distribution of Fukushima derived contamination in the northeast Pacific Ocean:

The temperature overlay highlights the anomalously warm water present in the northeast Pacific at present that we have found is marked with higher levels of Fukushima contamination. In the press this temperature anomaly has been referred to as “the blob”. You can read about it here in an very informative post by my colleague Dr. Richard Dewey of Ocean Networks Canada. A lack of vertical and horizontal mixing has allowed the ocean to retain this heat which further suppresses mixing. This is likely leading to significant ecological consequences in our part of the Pacific like decreased production, species shifts and nuisance algal blooms.

Laura disembarked the CCGS Sir Wilfrid Laurier in late July in Barrow Alaska and samples were shipped back to the laboratory for radionculide analyses using a highly sensitive gamma spectrometer. Results will be made available on the Fukushima InFORM project website when analyses are completed in a couple of months.

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