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View Diary: Fukushima: CA Universities Launch Kelp Watch 2014 (20 comments)

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    Jay Cullen's diary today expressing my opinion - and hope - that they'd consider strontium-90 as the benchmark radionuclide in all new studies (fish and seaweed), because we're now past 1,000 days and the cesium levels have pretty much reached equillibrium. Because its biological half-life is 70 days, at this point there shouldn't be any meaningful difference in food chain concentration in migratory predators despite even though there are considerable concentration differences between waters off Japan and those off California.

    Strontium, on the other hand, is a calcium substitute, and once incorporated into tissues stays there until it either decays or the organism dies. Thus steady and increasing levels from ocean releases at Fukushima will continue to bioaccumulate to higher and higher levels.

    Of the "big three" dangerous radioisotopes released by nuclear bombs/accidents in the most concentration, strontium is the most dangerous for deadly cancers (leukemias, bone cancers, organ cancers). With the presumption that thyroid cancers from iodine-131 are mostly "curable" these days (though debilitating). And at this point strontium concentration in the ongoing releases is essentially 1:1 with cesium.

    I also mentioned the problem with only giving a fraction of the contamination levels when reporting - cesium 134/137 only - and then writing it off to "less than K40 or Po210." There's a lot more contamination in the water and in the organisms than just the cesium sisters, so cesium reports do NOT reflect radiation dose from eating Pacific seafood. Nor does it reflect the fact that exposure from any and all Fukushima nuclides is in addition to the 'normal' levels of 'natural' background sources in that same seafood. Those never change.

    •  Hi Joieau (0+ / 0-)

      Please see my reply to your comment.  The amount of Sr-90 an organism will incorporate depends on the concentration of Ca2+, Sr2+ and Sr-90 in seawater.  The first two are not changing and the 3rds concentration despite continued release will not unless release rates increase dramatically.

      Cs isotopes bioaccumulate to a greater degree than does Sr-90 in marine organisms by a factor of 5-30 (link). That means at the same concentration there will 5-50 times more Cs in organisms than Sr.  But the concentration of Cs-137 is much, much higher in the plume given that initial releases of Sr-90 were about 3% of Cs.  Now after the initial releases Japanese marine fish were showing ~10's of Bq/kg Cs isotopes averaging around 18 Bq/kg excluding the immediate vicinity near to the reactors.  Sr-90 would be much lower given the lower concentrations.  A fish with 18 Bq/kg Cs-137 if ingested by a person imparts a dose of about 60 nanoSv per kg consumed.  If you increase the exposure by a factor of 10 from other radionuclides you get to roughly half a microSv. How much do you think looking at Cs alone underestimates dose? An order of magnitude? Two or three? The dose from 210-Po alone is over 23,000 nSv kg consumed.

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