Indoor radon concentration and a diffusion model in dwellings situated in a subalkaline granitoid area, Southern Brazil

G Romero-Mujalli,A Cordova-Gonzalez,A Roisenberg,P H P Stefano

doi:10.1007/s12665-021-09849-3

Abstract

Radon (Rn), a radioactive element, has especial interest in medical geology because long-term exposure to high concentration is related to lung cancer. In this study, outdoor and indoor radon measurements were conducted in dwellings of the Piquiri Syenite Massif, located in southern Brazil, given the relative high Rn content in soils of this region. Measurements were done using CR-39 detectors and placing them inside and outside dwellings. Moreover, a one-dimensional diffusion model was performed in order to quantify the natural transport of Rn to the air in confined and aerated environments. Results indicate that the region presents relatively low air Rn concentrations, within the environmental limits; however, the health risk might increase in confined and ill-ventilated environments because of transfer from soil and exhalation from ornamental rock-material often found inside dwellings. The main north facies of the syenite, where most of the rock extractions are located, was found to have the highest air Rn concentration because of the higher soil Rn concentration, compared to other facies of the syenite.

Highlights

Radon (Rn) is a noble gas found in the atmosphere, trapped between soil grains and dissolved in water
The outdoor Rn concentration obtained using the CR-39 detectors varies between 0.008 and 0.018 kBq m−3 that might represent the natural concentration expected in the region
It is worth noticing that in this study all indoor Rn concentrations measured by CR-39 detectors are lower than the maximum recommended limit of 0.3 kBq m−3 (World Health Organization 2009), which is equivalent to 10 mSv a−1

Summary

Introduction

Radon (Rn) is a noble gas found in the atmosphere, trapped between soil grains and dissolved in water. There are three naturally occurring isotopes of radon, each one associated with a different radioactive decay series, 222Rn (radon), which occurs in the 238U series, 220Rn (thoron) in the 232Th series and 219Rn (actinon) in the 235U series. Their direct parent atoms are 226Ra, 224Ra and 223Ra, respectively (Sextro 1994; Ferronsky and Polyakov 2012). Its occurrence is related with the mobility of 226Ra, which at the same time is related with the geochemical behavior of 238U (Appleton 2005)

Methods

Results

Discussion

Conclusion