Subj: Re: Cs-137 levels in South FL soils- ADDENDUM

[RADPROJECT@aol.com]

In a message dated 12/8/98 4:59:39 PM Eastern Standard Time, RADPROJECT
writes:

<<   I don't have the references right at hand but Cs-137 in FL was, if memory
serves me right, at peak about 50-70 mCi/km^2. From this one can derive an
average soil concentration based on RG 1.109 assumptions of soil depth,
density, etc. It would work out to about 150 pCi/kg of soil, give or take 50%
on average. >>

My memory is hereby corrected. The above value quoted was for Sr-90 areal
deposition, not Cs-137.  Since sending the above, I had a chance to check a
figure from a paper I delivered at an HPS Annual Meeting in Washington in 1991
["Cs-137 in Woodash -Results of Nationwide Survey"] which contained a figure
on Sr-90 deposition isopleths in the US per various published references.

The figure from an old AEC publication shows Sr-90 [not Cs-137] deposition of
60 to 70 mCi/km^2 at peak. The Cs-137 areal deposition across FL would thus
have been about 100 mCi/km^2 at peak concentration in the late 1960s, and
about half that level at present based on decay. I haven't derived an
estimated Cs-137 concentration, but it would probably be about 150 to 200
pCi/kg of soil at present

Of note, one subsequent measurement of a woodash sample from Gainesville, FL
[my wife's sister's  fireplace - hardwood ash] not reported in my HPS paper in
1991, had a Cs-137 concentration measured in 1994 at over 30,000 pCi/kg of
woodash, the highest concentration of Cs-137 in woodash measured anywhere in
the U.S.  This one data point is quite intriguing. 

FL soil generally has very low potassium and therfore probably has a very high
transfer of Cs-137 from soil to plant since there is an inverse relationship
between potassium and plant uptake of Cs-137 since plants have to struggle to
get enough K in low K soils and tend to suck up the Cs-137 which comes down in
fallout as carrier free Cs. In the 1960s, FL also reported some of the highest
Cs-137 concentrations in milk of any area of the US despite the fallout there
not being unusually high.

Reg. Guide 1.109 provides a value for the transfer factor from soil to plant
[the so-called Biv value : pCi/kg-plant/pCi.kg-soil) of 0.01]. Woodash
typically has an ash fraction of about 0.5 to 1% or about 100 to 200 parts
wood to one part ash. 30,000 pCi of Cs-137 per kg of ash thereby implies
[assuming no Cs loss on combustion!] a plant concentration of 150 to 300
pCi/kg. However, the soil concentration of Cs-137 in FL is likely to be
about150 pCi/kg. Thus the Biv for FL is about 1.0 to 2.0 not 0.01!! Thus any
dose calculations of terrestrial food pathways done for any unit Cs-137
deposition in FL using a RG 1.109 transfer factor of 0.01 is likely to be low
by a factor of from 100 to 200. 

This point should receive intensive study but it has never been investigated.
I tried to get the EPA a few years ago to fund an investigation of Cs-137 in
wood ash after my initial survey and paper at the HPS meeting. However, one of
the EPA reviewers discounted my proposal saying they didn't think there would
be any Cs-137 in trees despite measurements having been reported to me from
about 15 different institutions and facilities including the Princton Plasma
Physics Lab, various NBS traceable measurements at various utilities, etc.

I guess the old saying is true. "Don't try and teach a pig to sing. You only
waste your time and upset the pig"


Stewart Farber, MS Public Health
Public Health Sciences
Phone/FAX: 401 727-4947 
Email: radproject@usa.net
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