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Soil as a source of indoor 220Rn
Y Li1, S D Schery, B Turk
1Physics Department, New Mexico Institute of Mining and Technology, Socorro 87801.
Health Physics
|May 1, 1992
Summary
Soil beneath homes is a significant source of indoor thoron (220Rn). Mitigation systems that reduce soil gas flow effectively lowered indoor 220Rn levels by an average of 70% in four houses studied.
Area of Science:
- Environmental Science
- Indoor Air Quality
- Radiological Health
Background:
- Indoor radon (Rn) and thoron (220Rn) are radioactive gases that can pose health risks.
- Previous research has suggested building materials or soil as primary sources of indoor 220Rn.
- Limited data and measurement challenges have hindered definitive source identification.
Purpose of the Study:
- To investigate and provide evidence for the sources of indoor 220Rn in occupied homes.
- To quantify the contribution of soil gas to indoor 220Rn levels.
- To assess the effectiveness of subfloor depressurization in mitigating indoor 220Rn.
Main Methods:
- Continuous measurement of indoor 220Rn using a two-filter system.
- Measurement of 220Rn progeny with single filters and alpha-track detectors.
- Implementation of subfloor depressurization systems to block soil gas entry.
Main Results:
- Four out of seven houses showed significant reductions in indoor 220Rn levels when mitigation systems were active.
- An average reduction of 70% in indoor 220Rn was observed in houses with effective mitigation.
- One house showed no reduction, attributed to ineffective soil gas flow curtailment by the mitigation system.
Conclusions:
- Soil beneath houses is a significant and demonstrable source of indoor 220Rn.
- Subfloor depressurization is an effective mitigation strategy for reducing soil-derived indoor 220Rn.
- This study provides strong evidence supporting soil as a major contributor to indoor 220Rn concentrations.