Radon content in Danish till deposits: relationship with redox conditions and age

Radon (222Rn) is a radioactive, noble insoluble gas with a half-life of 3.8 days. It belongs to the uranium (238U) decay chain where radon is formed from radium (226Ra). Uranium and radium are built into mineral structures or are, for example, adsorbed on the surface of clay minerals, limonite or organic material. When radon is formed by radioactive decay from radium, parts of it enter the pores of rocks and soils and are transported by diffusive or advective forces in the pores. The transport rate depends on the permeability and water content in the pores (Nazaroff 1992)