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Fukushima

By Bill Hauser

When people learn that I am a fishery biologist in Alaska, one question I am often asked is about radioactivity released from the Fukushima power plant that is (or, may be) drifting toward Alaska. Here is some information I have recently learned. . . [My additions, below, are in italics.]

On March 11, 2011, a massive 9.0 magnitude earthquake triggered a tsunami off the coast of Japan, severely damaging the Fukushima Dai-ichi Nuclear Power Plants resulting in the discharge of a radioactive plume into the atmosphere and ocean. The radioactive material that entered the ocean moved eastward towards North America via the Kuroshio and North Pacific current systems.

A paper published in December 2014 in the Proceedings of the National Academy of Sciences (PNAS) details the arrival and concentration of radioactive isotopes from the Fukushima nuclear reactor in the North Pacific Ocean. This paper, by the Canadian Department of Fisheries and Oceans scientist Dr. John Smith, documents the first and only systematic study of its kind validating ocean circulation models while tracking the eastward movement of radioactive isotopes.

Fisheries and Oceans Canada (DFO) established an ocean monitoring program using radioactive cesium isotopes Cs-134 and Cs-137 to validate ocean circulation models and trace the arrival of Fukushima radioactivity in the Pacific and Arctic Oceans. Between 2011 and 2014, DFO researchers on board the Canadian Coast Guard Ship John P Tully took measurements of radioactivity along Line P, a research transect, which extends 1500 km (935 miles) westward from Victoria, B.C. to the interior of the North Pacific. Samples were also collected in the Beaufort Sea in 2012 to check for the presence of Fukushima radiation in the deep Arctic Ocean by DFO scientists on the Canadian Coast Guard Ship Louis S St. Laurent.

In June 2012, about 1.3 years after the accident, a small amount of Fukushima Cs-134 was detected at the western end of Line P. Measurements of this short-lived isotope indicate that the source is from Fukushima and allows researchers to then determine what portion of the longer-lived isotope (Cs-137) comes from Fukushima and what portion was pre-existing. By June 2013, Cs-134 was detected in surface waters all along Line P to the Canadian continental shelf.

Ocean circulation model estimates indicate that future total levels of Cs- 137 off the North American coast will likely peak at 3-5 Bq/m3 (Becquerel per cubic meter) (one cubic meter is equal to 35.3 cubic feet) by 2015-2016, before declining to levels closer to 1 Bq/m3 by 2021. The increase in Cs-137 levels in the eastern North Pacific from the Fukushima reactor will probably return to background radiation levels that prevailed during the 1980s. Cesium-137 exists in the Pacific Ocean at a background level of approximately 1 becquerel per cubic meter of water. Since the Fukushima incident, radiation levels off the BC coast have increased to about 2 becquerels and its expected to peak in 2015-16 at about 5 becquerels per cubic meter of water. To put that in perspective - Canada’s standard for Cesium-137 in drinking water is 10,000 becquerels per cubic metre meaning that the increase in Cesium-137 in Canadian Pacific waters do not represent a threat to human or animal health. (Bold emphasis is mine, WJH.)

While these results suggest that Fukushima-generated radiation levels do not represent a threat to Canada (Bold emphasis is mine, WJH.), studies such as these allow scientists to better assess potential impacts on human health and the environment now and in the future.

OK. So what does this mean for Alaska? Radioactivity is traveling eastward from Japan to North America by way of the North Pacific Current which is at about 40 to 50 degrees north latitude. This means that it arrives on our continent at a latitude of about the State of Oregon to southern British Columbia where it splits into the southbound California Current and the northbound Alaska Current. I interpret this to say that expected radioactivity in Alaska waters will be less than in Canadian coastal waters.

In February, 20, 15, the Alaska Department of Environmental Conservation reported, “results of testing conducted on Alaskan fish in 2014 results showed no detection of radionuclides from Fukushima. However, scientists predict that the peak concentrations of radionuclides in water will reach the North Pacific in 2015” and testing of fish for evidence of radioactivity will continue in 2015. You can see more at their website: http://dec.alaska.gov/eh/radiation/.

Date modified: 2014-12-30 (my comments, March 10 - 14, 2015)

Alaska Fly Fishers, 200 W 34th Ave, Suite 1233, Anchorage, AK 99503

 
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