Partitioning of 222Rn entry into a structure surrounded by soil

Area of Science:

• Environmental Science
• Geophysics
• Building Science

Background:

• Radon (222Rn) is a naturally occurring radioactive gas that can accumulate indoors.
• Understanding radon entry mechanisms is crucial for mitigating indoor air quality issues.
• Basement structures are particularly susceptible to radon ingress due to soil contact.

Purpose of the Study:

• To quantify the entry rate of radon (222Rn) into a basement.
• To identify the primary pathways and origins of radon ingress.
• To elucidate the transport mechanisms driving radon entry under varying conditions.

Main Methods:

• In-situ measurements of radon concentrations and entry rates.
• Analysis of radon origins, including contribution from concrete.
• Identification of radon transport mechanisms (diffusion and convection).

Main Results:

• The highest indoor radon concentrations were observed when the radon entry rate was at its lowest.
• Radon entry occurred primarily through the floor and walls (75%) and the floor-wall joint (25%).
• Approximately 30% of the radon originated within the concrete structure itself, with diffusion as the main transport mechanism.

Conclusions:

• Radon entry dynamics are counterintuitive, with higher concentrations linked to lower entry rates.
• Both diffusion and convective flow play roles in radon transport, particularly at the floor-wall joint.
• The concrete material contributes significantly to the indoor radon budget.