Re: Cs-137 in soil

[Les Fraley <les@lamar.ColoState.EDU>]

On Thu, 7 Nov 1996, Gary Schroeder wrote:

> >Is CS-137 left over from the above ground weapons testing?
> >Yes.  About 50 % of the original fallout still remains, although it has 
> >been redistributed to a certain degree.  It is still possible to find 
> >137-Cs in surface soil samples, especially in undisturbed locations 
> >such as untilled pastures and graveyards.
> >Les Fraley
> 
> Les, it's most certainly observable in locations other than untilled fields
> and graveyards!  Besides, natural erosion mechnisms like wind and rain are
> far more influential than tilling when you're considering a time scale of
> decades.  Go grab a few hundred grams of dirt from your back yard.  It may
> be less than a pCi/g, but you'll find it with a high efficiency HPGe detector.
> 
> 
> ===============
> Gary L. Schroeder
> Brookhaven National Laboratory
> gs1@bnl.gov
> 
Gary,
  You are quite right, of course.  I didn't mean to imply that 137-Cs 
could not be found other places, just that the locations mentioned would 
be easy places to locate it, especially with modest equipment.
  The issue about redistribution is a little more tricky.  Not that it 
has not become redistributed; it has.  Exactly how and to what extent the 
redistribution has taken place, and which mechanisms were responsible, is 
another matter.  I have read papers that report on the extent of erosion 
measured based on 137-Cs concentrations in soil.  All such research, 
however, is based on uniform distribution when the 137-Cs was originally 
deposited.  I don't accept that.  I have yet to see any report that 
indicates the degree of uniformity from fallout deposition was actually 
measured.  It has been extablished that, at least in these parts, the 
original deposition was not uniformly distributed.  This can also be 
inferred by observing snowfall patterns; and snow is an excellant 
scavinger of airborne particles, including fallout.  This non uniformity 
holds for both the mountains and the plains.  Rain, even though more 
uniform (at least on the plains) than snow, is not uniformly deposited.  
In addition, the deposition occured over a several year period.  This 
further complicates the problem of trying to measure erosion rates using 
137-Cs.
  Just some thoughts.  Les Fraley