What happens to radon levels during periods of reduced soil permeability?

During periods of reduced soil permeability, radon levels tend to increase due to the way radon is generated and can move through the soil. Radon is a radioactive gas that emanates from the decay of uranium and thorium found in soil and rock. When soil permeability is low, the movement of gases, including radon, can become restricted.

This restriction can lead to a buildup of radon in the areas beneath structures, as the gas finds it more difficult to escape into the atmosphere. Additionally, if the permeability is reduced due to factors such as increased soil moisture or compaction, the radon gas can accumulate in higher concentrations in and around the foundation of buildings, leading to increased indoor radon levels.

The other choices do not accurately reflect the behavior of radon in conditions of limited soil permeability. For instance, decreased radon levels would not be observed as the gas is not dissipated effectively. Stabilization and inconsistency of levels are also unlikely, as the primary effect of reduced permeability is an increase in concentration due to the limitation of radon escape routes. Therefore, the only accurate response to the question is that radon levels increase during these conditions.