Diurnal and seasonal variability of outdoor radon concentration in the area of the NRPI Prague

Study of variation of indoor radon levels in houses and prediction of indoor concentrations using house characteristics and outdoor radon levels

The measurement of 222Rn concentrations in indoor and outdoor air was carried out in certain locations of Mandya city, Karnataka, using the Solid State Nuclear Track Detectors (SSNTD) technique. The annual mean values of 222Rn in indoor and outdoor are found to be 20.5 ± 1.4 and 9.0 ± 0.5 Bq m-3, respectively. The observed mean value of indoor radon concentration is found to be well within the world and the Indian average of 40 and 42 Bq m-3, respectively. Outdoor radon concentrations have been measured in the vicinity of houses where yearlong radon measurements carried out using the SSNTD technique. The seasonal variation in the outdoor radon was studied and the average concentrations during summer, rainy and winter are 9.1, 6.9 and 12.9 Bq m-3 respectively. Considering the possible factors such as house characteristics (Volume, Surface area of building material, Leakage area, etc.), indoor-outdoor temperature difference and outdoor radon concentration into account, the indoor radon levels were predicted using the existing model which is based on the mass balance equation. The results are systematically analysed and discussed. The predicted values are compared with the measured values.

Residential radon exposure and seasonal variation in the countryside of southeastern Brazil

Poorly ventilated environments such as residences can accumulate radon gas to levels that are harmful to humans and thus produce a public health risk. To assess the risk from natural radiation due to indoor radon exposure, ²²²Rn measurements, using an alpha RAD7 detector, were conducted in Timóteo, Minas Gerais state, southeastern Brazil. Indoor radon concentrations, along with meteorological parameters, were measured every 2 h during both wet and dry seasons in 2017 and 2018. The mean concentration of indoor radon varied between 18.0 and 412.8 Bq m^-3, which corresponded to an effective annual dose of 1.2 and 7.6 mSv y^-1. Average radon concentrations were significantly higher during the winter dry season, and there was a strong positive correlation with humidity in both wet and dry season. Furthermore, concentrations showed an inverse correlation with atmospheric pressure, wind speed, air temperature, and solar radiation. The radon levels are generally above the limits recommended by international standards, meaning that mitigation measures are needed to improve air quality to reduce human exposure and risk. Finally, through the statistical analysis, it was possible to determine the differences and similarities between the sampling points concerning the geology of the place and the geographical location.

On the relation between outdoor 222Rn and atmospheric stability determined by a modified Turner method

In practice, information about atmospheric stability is often obtained from discrete stability classes determined from routine meteorological observations. However, changing concentrations of the radioactive gas ²²²Rn present in the atmosphere are also considered a good indicator of vertical dispersion and atmospheric stability. A complex, in-depth analysis between these different approaches of atmospheric stability assessment has not been performed so far, and was the main motivation behind this study. The study presents atmospheric radon data measured in Bratislava (Slovakia) and stability indexes (SI) calculated according to a modified Turner method during a period of one year. Basic features of the diurnal and seasonal variations of these variables are discussed. It was found that the time series of radon activity concentration (RAC) lags approximately 5 h behind that of the Turner stability classes adjusted for temperate climate regions. Various time lags were also identified between RAC and meteorological variables used to determine the stability classes. Evaluation of seasonal trends revealed a low variability of mean monthly values of stability classes compared to the variability of mean monthly values of RAC. Another notable difference between RAC and stability indexes was found - while the stability index can both increase and decrease with wind speed, concentration of outdoor radon was never observed to increase with increasing wind speed. In spite of the mentioned discrepancies, the time series of RAC and SI are generally in a good agreement. This is especially true if one compares the deviations of RAC and SI from their mean daily values, when the differences in their seasonal variability are eliminated. Deviations of RAC can be used to calculate diurnal variations of stability indexes. Analysis of a complete year of data also revealed a roughly linear relationship between average values of RAC and calculated stability indexes, because in large datasets random processes tend to cancel each other out.

Thermo-diffusional radon waves in soils

A new theoretical framework for diurnal and seasonal oscillations of the concentration of radon in soil and open air is proposed. The theory is based on the existing temperature waves in soils and thermo-diffusional gas flux in porous media. As soil is a non-isothermal porous medium, usually possessing a large fraction of microscopic pores belonging to Knudsen's free molecular field, a thermo-diffusional gas flow in soil has to arise. The radon mass transfer equation in soil for sinusoidal temperature oscillations at the soil-atmosphere boundary is solved, which reveals that radon concentration behaves as a damped harmonic wave. The amplitude of radon concentration oscillations and phase shift between radon concentration oscillations and soil temperature depend on the radon diffusion coefficient in soil, rate of radon production, soil thermal conductivity, average soil temperature, decay constant, and heat of radon transfer. Primarily numerical calculations are presented and comparisons with experimental data are shown.