Diurnal variations of indoor short-lived radon daughters with positive ²¹⁸Po and ²¹⁴Pb clusters and their impact on atmospheric air ions

Area of Science:

• Environmental Science
• Radiological Protection
• Atmospheric Physics

Background:

• Airborne radon progenies (²¹⁸Po, ²¹⁴Pb, ²¹⁴Po) are radioactive aerosols and a major source of natural indoor radiation exposure.
• These radionuclides influence environmental ionization and aerosol characteristics, necessitating accurate indoor measurements for air pollution assessment.
• Understanding radon progeny behavior is crucial for public health risk assessment and mitigation strategies.

Purpose of the Study:

• To conduct continuous indoor measurements of airborne radon progeny (²²²Rn, ²¹⁸Po, ²¹⁴Pb, ²¹⁴Po) in El Jadida, Morocco.
• To analyze diurnal and seasonal variations in radon progeny concentrations and their relationship with meteorological parameters.
• To calculate radon-linked ionization rates and air ion concentrations.

Main Methods:

• Continuous indoor monitoring at 2-hour intervals across seasons (2023-2024) in El Jadida.
• Aerosol sampling on filters followed by alpha-counting using CR-39 nuclear track detectors (three-count approach).
• Development of PC-based software to solve differential equations using experimental data for physical quantity calculation.

Main Results:

• Annual average concentrations: ²²²Rn (80.2 ± 6.6 Bq/m³), ²¹⁸Po (44.0 ± 3.6 Bq/m³), ²¹⁴Pb (34.5 ± 2.8 Bq/m³), ²¹⁴Po (24.3 ± 2.0 Bq/m³).
• Significant diurnal variations (3-4 times) with morning maxima and afternoon minima; seasonal variations (30-50%) peaking in colder months.
• Annual averages for radon-linked ionization rate and air ion concentration were 27.9 ion-pairs cm⁻³ s⁻¹ and 2113 ions/cm³, respectively.

Conclusions:

• Indoor radon progeny concentrations exhibit significant diurnal and seasonal variability, influenced by meteorological factors.
• The study provides essential data for assessing indoor air quality and natural radiation exposure in the region.
• Approximately 52% of ²¹⁸Po and 49% of ²¹⁴Pb clusters were found to be positively charged under normal home conditions.