Question Answered by Arthur Rood, President K-Spar Inc.
Radon-222 is a tasteless, odorless gas formed by the decay of radium-226. Radium-226 is a naturally occurring radioactive element that is present in most soils and masonry building materials in small quantities. Typical radium-226 concentrations in soil range from 0.5 to 2 picocuries per gram, but in some places can be as high as 5 to 10 picocuries per gram depending on the geology. A picocurie is a measure of radioactivity and is 0.0000000000001 of a Curie. The radon formed from radium-226 in soil can migrate through soil pores, cracks in cement, and other pathways into the home. Radon-222 has a half-life of 3.82 days, so increasing the time it takes for radon to migrate from the soil into your home is important in determining radon concentrations in homes. Depending on many factors including soil moisture, cracks in your cement foundation, and home ventilation, background radium-226 concentrations in soil and building materials can result in varying levels of radon-222 concentrations in your home.
The EPA recommends that the annual average radon concentration in a home be no more than four picocuries per liter of air. Radon has been known to cause lung cancer in early uranium miners who worked in unventilated mines where radon concentrations were tens of thousands picocuries per liter. Radon concentrations in homes are many times less than this and can be reduced by sealing cracks in basement foundation and adding basement ventilation to remove radon from the home.
Radon originates from uranium, a solid element commonly found in bedrock. Almost anywhere in the world you can find some radioactive uranium in the soil. Radioactive simply means that an unstable atom emits a particle and changes into a different element. The energy released as the atom changes is known as radioactive decay. Uranium goes through a number of decays before becoming radon. All the elements before and after radon are solids. Radon, however, is a noble gas which means it can freely move through the soil. Radon moves more rapidly through permeable soils, such as coarse sand and gravel, than through impermeable soils, such as clays, but fractures in any soil or rock allow radon to move more quickly.
Materials: clear plastic box, hammer, nail, puffed rice cereal, broken cookies, chocolate chips, small sprinkles, coconut, blow dryer
- Have an adult help you punch some holes in the bottom of the plastic box using a nail and hammer.
- Cover the bottom of the box with broken cookies. This represents the fractured bedrock layer.
- Add a layer of puffed rice cereal. This represents the limestone layer.
- Add a layer of chocolate chips. This represents the sand and gravel layer.
- Add a layer of sprinkles. This represents the fractured clay layer.
- Add a final layer of coconut. This represents the sand and silt layer.
- Turn your blow dryer on the cool setting and blow air through the holes in the bottom of the plastic box. Does your model show that radon gas could travel upwards