Seasonal and spatial variations in Rn-222 and Rn-220 in soil gas, and implications for indoor radon levels

Area of Science:

• Environmental Science
• Geology
• Radiological Protection

Background:

• Radon-222 (Rn-222) gas enters dwellings via soil gas, driven by pressure differentials.
• Understanding soil gas emanation is crucial for indoor radon mitigation.

Purpose of the Study:

• To investigate radon (Rn-222 and Rn-220) emanation pathways and influencing factors in soil.
• To identify specific soil characteristics affecting radon transport into dwellings.

Main Methods:

• Field measurements of radon isotopes (Rn-222, Rn-220) in soil gas at varying distances from a dwelling.
• Correlation analysis with environmental factors like wind run, temperature, and soil type (Northampton Sand Ironstone).

Main Results:

• A preferred radon-222 emanation pathway (hotspot) was identified, showing distinct concentration differences.
• Radon-222 concentrations exhibited a strong negative correlation with wind run, indicating wind pressure reduces soil radon.
• Radon-220 (Rn-220) showed positive correlations with grass and air temperatures but was not linked to the Rn-222 hotspot.

Conclusions:

• Soil gas emanation, particularly Rn-222, is influenced by geological features and meteorological conditions.
• Wind pressure is a significant factor in reducing soil radon concentrations at shallow depths.
• Rn-220 behavior differs from Rn-222, being more influenced by temperature than specific geological pathways.