Re: radon measurements in soils

[DHINTEN@nervm.nerdc.ufl.edu]

Sergio,
     Radon measurements in soils have proven to be somewhat difficult to
use as predictive measures for potentially elevated indoor radon concentrations
in many instances due to the great number of variables that can ultimately
affect the transport and entry.  We have had relatively good success by
utilizing two sets of measurements, soil radium and soil gas radon.  Soil
radium profiles provide a quantitative measure of the source potential and
are usually obtained from core samples and analyzed with gamma spec to
determine radium content (activity/gm).

Even with a large source potential there still may not be a problem because
the radon must be able to emanate from the source soil and subsequently
be transported through the surficial soil layers, which involves variables such
as the soil permeability, water content, etc.  Measurements of the soil gas
radon concentration measure the radon available for transport into a structure.
It is typically measured by pumping soil gas from approximately a 1 m depth
at known pressure or flow (thus providing a standard for different soil
permeabilities) and measuring the radon concentrations in the soil gas
(activity/volume).  While soil gas radon is more variable due to rainfall,
and other environmental conditions, I believe it provides a more consistent
measure if performed during "typical" weather conditions.

A number of radon mitigation/measurement companies in the U.S. offer these
measurements locally.  You might consider Rogers and Associates Engineering
in Salt Lake City, who have alot of experience and have performed these
measurements on a national scale.

Dr. David E. Hintenlang
Health Physics Program Coordinator
Department of Nuclear Engineering Sciences
University of Florida