Is high indoor radon concentration correlated with specific activity of radium in nearby soil? A study in Kosovo and Metohija

This paper presents indoor radon concentrations and specific activities of natural radionuclides measured in soils of Kosovo and Metohija. The measurements of radon concentration were performed during two consecutive 6-month periods in two rooms of 63 houses using CR-39 detectors. The annual radon concentration ranged from 30 to 810 Bq m⁻³ with the average value of 128 Bq m⁻³. Almost 15% of the houses had radon concentration higher than 200 Bq m⁻³. The difference between radon concentrations measured in the two 6-month periods was analyzed, showing, as expected, a slightly higher radon concentration in the “winter period” than in the “summer period”. The variation between different rooms of the same houses was also analyzed, showing that 20% of the dwellings had a significantly higher radon concentration (>100 Bq m⁻³) in one room compared to the other (the coefficient of variation ranged up to 96%). The specific activities of natural radionuclides in the nearby soil were determined by gamma spectrometry. The estimated average value (and standard deviation) of ²²⁶Ra, ²³²Th, and ⁴⁰K specific activities were 32 (13), 35 (16), and 582 (159) Bq kg⁻¹, respectively. The correlation between indoor ²²²Rn and ²²⁶Ra content in soil was investigated. Only a weak correlation was found (Spearman’s rho = 0.220) indicating that other factors might affect diffusion and accumulation of radon indoors, as confirmed also by the high variability between the rooms of the same houses.