Rough bq/m2 for Boise, Idaho

As much as I have hated this whole FK thing, it has made me interested in science again. Because basically, science is the only way to understand this, and understanding is key.

So I thought, I wonder what the ground depostion of cesium in say, Boise ID might be. We have all seent he maps of Fukushima and Chernobyl, with levels in kBq/m2 (and sometimes more). A good part of Europe took on 10-40 kbq/m2 from Chernobyl in Cs-137. How can I halfway figure that the amount might be in Boise?

I used the following data set - during the time the EPA was testing rainwater in Boise (which had the by far the most "rain-out" of any of the stations), there were two times when cesium was detected, 3/22 and 3/27. On the worst sample, the levels were 42 pCi/L of Cs-134 and 36pci/L Cs-137, for a total cesium activity of 78 pCi/l (bear in mind that I am using both 134 and 137, most maps show 137 only so I am skewing the data towards worst case). If you convert the 78 pCi/L to bq, you get 2.886 bq/l in cesium activity.

Now I checked weather underground for archival precip data for Boise, and between 3/15 and 3/31, Boise recieved 1.33 in of rain. Converted to metric, that is .0338 meters of rain. To find the amount of rain that fell on a square meter, multiply .0338m X 1 meter X 1 meter = .0338m3 of rain per square meter during the last two weeks of March.

.0338m3 = 33.8 liters. 33.8 liters at an activity of 2.886 bq/l = 97.54 bq/m2 of combined cesium activity from rain was deposited in Boise, ID. Please note that is bq, NOT kBq.

I did use some assumptions, all of them worst case -

1) That all of the rain that fell in Boise was as bad the worst sample. In fact, the two measurements recorded vary significantly, with lower measurement showing about 35% of the levels of the higher one.

2)I used Cs-134 AND C-137.

One big unknown here is how much was deposited by "air". I have read that rainouts are the largest contributor to fallout. Can anyone provide a ratio, or is there even such a thing?

So the take-away for me is that Europe survived a hell of a lot worse fallout than the US has received thus far. Of course, the data set I used was limited, but I made it as ugly as I could. Had I used only the Cs-137 (like the Chernobyl numbers) or averaged out the rainfall activities, I could have shown a number about 30% of what is shown here.

Bear in mind that this was the worst sample, a great many of the rain samples didn't show anything. The flip side is that there are probably worse samples that could have been taken in spots that we may not even suspect. A huge amount of testing should be done, but it won't, so there ya go, but at least the info we have suggests that the risks here in the US are low (kinda like the BRAWM guys have been saying :).

BTW, I am not minimizing the concerns that all of us have, and will add that A) Northern Japan is hosed mightily and B)we need to power this crap down while we still can, lest the worst of our fears come to pass.

Note this archival data, more at the Davistown Museum site which I think was originally referrenced by Tdm.

Juzdan, Z.J., Helfer, I.K., Miller, K.M., Rivera, W., Sanderson, C.G. and Silvestri, S. (1986). Deposition of radionuclides in the northern hemisphere following the Chernobyl accident. In: Environmental Measurements Laboratory: A compendium of the Environmental Measurements Laboratory's research projects related to the Chernobyl nuclear accident: October 1, 1986. Report No. EML-460. U.S. Department of Energy, New York, NY.

May 5, 1986 Forks, WA Wet and dry deposition 137Cs 301.55 Bq/m2
May 5, 1986 Forks, WA Wet and dry deposition 131I 1200 Bq/m2
May 5, 1986 Forks, WA Wet and dry deposition 103Ru 134.68 Bq/m2
May 5, 1986 Forks, WA Wet and dry deposition 134Cs 72.89 Bq/m2