Potassium 40 variation in soil

["Bjorn Cedervall" <bcradsafers@hotmail.com>]

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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