Re: Los Alamos Wildfires -Airborne radioactivity news coverage

[Chris Alston <alstonc@odrge.odr.georgetown.edu>]

Please note that the naturally occurring elements uranium, thorium, and
radium, and their progeny, some of the latter of which are reasonably
long-lived (i.e., days), are alpha- and beta-emitters. Of course, there are
also gammas associated with these. The primordial radionuclide potassium-40
decays (% = 89.3) by emitting a large beta (max E = 1.3 MeV). There is,
too, a 1.46 MeV gamma, from the electron-capture mode of decay (% = 10.7).
Carbon-14 and hydrogen-3 (both beta-emitters) are found everywhere. Some of
this is natural, and some is from the testing of nuclear weapons. Plants,
*naturally*, cannot tell the difference. I'm sure that we all have heard of
the dating methods that archeologists and paleontologists use, which rely
greatly on this uptake. Plants also take up, from the soil and the air, the
heavier natural radionuclides.

Foliage and fruits are excellent sources of potassium, as is common
knowledge. The specific activity of K-40 is ~800 pCi/g; that is, each gram
of regular potassium contains 800 pCi of radioactive K. In point of fact,
as I've noted before in this forum, I have used cartons of orange juice to
provide energy-calibration points for gamma spectrometers (when one is
poor, one must make do).

So, intuitively, there would be good reason to see increased levels of
radioactivity, as a result of a forest fire. To anyone who wants the *real*
lowdown on natural radiation, I highly recommend (again):

Eisenbud, M. and Gesell, T.; Environmental Radioactivity, 4th edition;
Academic Press; San Diego 1997; ISBN 0-12-235154-1.

Happy reading
cja
alstonc@odrge.odr.georgetown.edu


At 02:00 PM 5/18/00 -0500, you wrote:
>. . . that the smoke contains only natural radioactivity, 
>despite a 10 fold elevation in measured airborne gross alpha, a 2 fold 
>increase in gross beta, and some unspecified increase in gross gamma
activity 
>in air particulates.
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