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RADON:
WHAT IS IT?
Radon is a radioactive, colorless,
odorless, tasteless gas produced by the natural breakdown of radioactive
elements in soil and rocks. There are many ways to test soil and rock to
determine whether the material contains radioactive elements, and therefore
identify areas which may have higher levels of radon.
One method for radioactive
material detection is with aerial gamma-ray data collection. A gamma-ray
detector mounted on an aircraft is flown over an area of interest and the
amount of radioactive elements in the area can be calculated. To read more
about this method and about the U.S. Department of Energy’s National
Uranium Resource Evaluation program, click
here.
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Radon from Uranium
Levels of radon vary from place to place and even from
house to house within a given area. The higher the uranium content of the
rocks that underlie an area, the greater the likelihood that houses in the
area will contain elevated levels of radon.
Because
radon is a gas, it can migrate through rocks and soils, escaping into
fractures and openings in rocks and into ground water.
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FROM GROUND TO YOU
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Radon Potential
By evaluating the geology in an area, scientists can
evaluate the radon potential of the rocks and soils at housing sites or
other areas of interest. The factors listed below can increase the
probability that an area will have above-average levels of radon.
1. Uranium-rich rocks underlie the area.
2. The site is located on a hill or slope.
3. Soils are well drained or dry most of the time.
4. Soils form deep cracks during dry time of the year.
5. Highly permeable soils are present.
6. The soils are thin and bedrock is close to the
surface.
7. Underlying rocks are fractured.
8. The underlying rock contains limestone caverns.
9. High levels of indoor radon have been reported in
the county or neighborhood.
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Radon from Ground to Home
Radon moving through soil near the earth's surface
usually escapes into the atmosphere, although some of it may seep into our
homes through construction joints, cracks in the foundation, or the water
supply. Even if the soil air contains only moderate levels of radon,
concentrations inside houses may be high.
The U.S. Environmental Protection Agency's action
level (the level at which steps should be taken to reduce radon) is 4
picocuries per liter of air (pCi/L). About 1 out of every 15 houses in the U.S.
has radon levels exceeding the recommended action level.
The only way to know if you
have a radon problem is to test. Click here to
learn more about how to test for radon.
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RADON
IN ALABAMA
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Radioactive Geology
In Alabama, areas
that have higher uranium concentrations include the Appalachian Mountains,
the Cumberland Plateau, and the inner Gulf
Coastal Plain. Faults in granite and shale in the Appalachians
contain elevated uranium. The inner Coastal Plain units contain sands with
glauconite, a clay mineral high in uranium. Karst areas in north Alabama overlie the
Chattanooga Shale Formation which contains a high level of uranium. In the
map to the right, you can see the levels of radon are also correlated with
these higher uranium areas.
The most radioactive geologic unit in Alabama is the Upper
Devonian age Chattanooga Shale formation (above). The Chattanooga Shale is
a brownish-black to grayish-black silty, organic shale and fine grain
sandstone. Outcrops of this unit occur in the northern and eastern parts of
the Plateaus and in the Valley and Ridge. Roadcut exposure of Chattanooga
Shale (black layer) near Goose Pond in Jackson County, Alabama.
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To
see radon test results for your county, click here.
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Geological Survey of Alabama
geologist by an outcrop of Chattanooga Shale near Duck Springs in Etowah County, Alabama.
Related information on the research conducted in relation to this photo can
be found in “Geological foundation for production of natural gas from
diverse shale formations” by J. C. Pashin, D. C. Kopaska-Merkel, A. C.
Arnold, and M. R. McIntyre, (2011), Research Partnership to Secure Energy
for America (RPSEA) Final Report 07122.17.01.
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Chattanooga Shale as seen through the
microscope. To examine the tiny particles that make up the shale, a sample
of rock is glued to a microscope slide and ground down until thin enough to
pass light through it in order to see the individual mineral grains. Q =
quartz, R = radiolarians (a type of marine microfossil). Black areas are
matrix that contains a fine residue of uranium. This sample was taken from
the outcrop pictured to the left.
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ADDITIONAL INFORMATION
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Testing
for Radon in Your Home
There are many kinds of inexpensive, do-it-yourself
radon test kits available through the mail and in hardware stores and other
retail outlets. Be sure to buy a kit that is approved by the U.S.
Environmental Protection Agency (USEPA). Short-term tests may take as
little as 2 days and are generally performed in the lowest level of the
home.
Click the video to the left (or
click here) to learn more about radon in homes and how you can test for
radon in your home. To read more information on radon and radon in Alabama, click the
links below to the USEPA and U.S. Geological Survey.
http://www.epa.gov/radon/index.html
http://www.epa.gov/radon/states/alabama.html
http://energy.cr.usgs.gov/radon/radonhome.html
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