RE: Potassium 40 variation in soil

["Heinmiller, Bruce" <heinmillerb@aecl.ca>]

The 400-Bq/kg for K-40 in soil is the number quoted in NCRP-94.  If this was
the source and you're using NCRP-94 for Th-232 and U-238 data, be careful,
as it appears that the 66-Bq/kg quoted for U-238 in soil, from Table 4.3 of
that report is incorrect.  The evidence that I offer for this is the
following.  The 1.8-ppm quoted corresponds to 22 Bq/kg which is consistent
with NCRP-45 which gives 0.6 pCi/g which is also 22 Bq/kg.  You'll also note
that the 1.8-ppm figure is in the range of the various data quoted for ppm
U-238 in rocks, whereas the 66-Bq/kg is not; it is greater than any of the
corresponding data for U-238 in rocks, and this seems unlikely to me if soil
is a combination of weathered rock plus organic matter.  In none of the
other data in that table for nuclides in soils and rocks does the soil
specific activity exceed all of the corresponding data that are given for
rocks.

Bruce Heinmiller CHP
heinmillerb@aecl.ca

> ----------
> From: 	Bjorn Cedervall[SMTP:bcradsafers@hotmail.com]
> Reply To: 	radsafe@romulus.ehs.uiuc.edu
> Sent: 	Monday, November 08, 1999 6:59 PM
> To: 	Multiple recipients of list
> Subject: 	Potassium 40 variation in soil
> 
> I have this one number of 400 Bq K-40 per kg in soil. Guess that "soils"
> can 
> vary in composition quite a bit. Can anyone give me an idea about the 
> natural variation - or give me a hint about some relevant website? (I am 
> also interested in values for granite and other major rock types). The
> same 
> question is for Th-232 and U-238. This is for educational purposes - to 
> teach people about natural radioactivity. Thank you in advance for any
> help.
> 
> Bjorn Cedervall    bcradsafers@hotmail.com
> 
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