# A Case Study of the Radon Hazard at the Boundary of a Coal Minefield
###### Abstract  
The main purpose of this study is to assess the radon hazard in areas near the boundary of a coal mine. Our assessment included an analysis of the soil's radon volume activity (VAR) and radon flux density (RFD), as well as their spatial characteristics and correlations with other factors. The soil VAR varies in the range from 3477.7 to 17,520 Bq/m\({}^{3}\) (mean value 9786.9 \(\pm\) 474.9 Bq/m\({}^{3}\)), and RFD from 10 to 160 mBq\(\cdot\)m\({}^{-2}\cdot\)s\({}^{-1}\) with a mean value of 59.76 \(\pm\) 2.45 mBq\(\cdot\)m\({}^{-2}\cdot\)s\({}^{-1}\). The RFD parameter is spatially clustered (\(p\leq 0.01\)). No significant differences between RFD and soil VAR were found, both inside and outside the minefield areas (\(p\geq 0.05\)). However, we suggest considering the entire studied space of the minefield boundaries and surroundings to be radon-hazardous. This contributes to the understanding of the radon hazard of coal mines for ground structures both in the mine area and in its surroundings. coal mine; soil radon; radon flux density; tectonic faults; radon exhalation; Kuznetsk coal basin +
Footnote †: journal: _Sciences_  
0000-0002-4000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-  
Radon extraction from soils can vary drastically within one area with a homogeneous geological structure. This variation is caused by soil porosity, water saturation, and temperature. Also, faults and rock fractures caused naturally by technogenic activity create additional ways for radon to migrate to the surface [6; 7; 8; 9; 10]. All rocks can be classified as fissure-pore formations. Radon is emitted from rocks into pores and crack spaces, and some of it goes into adsorbent and absorbent. Tectonic disturbance areas exhibit a greater volume of fissure-pore space, facilitating the accumulation of noteworthy amounts of liquids and gases, such as radon. Radon is subsequently transported from these voids to the surface by means of diffusion, convection, and other forces. Accompanying gases, particularly methane and hydrogen, play a crucial role in stimulating the migration rate of radon. Alterations to the stress-strain state of rocks cause significant changes to the volume of the pore-crack space. The compression zone results in a decrease, while in the tension zone, an increase occurs. Consequently, this leads to a low volume of radon and a low capability to move to the surface along the fault zone. Active faults generally exhibit significant variation in the radon field above them, while inactive faults tend to be more stable or not evident at all [11; 12; 13; 14; 15]. Previous research has shown that an area with significant soil radon concentration, which emanates to the surface, forms above the fault zone. This radon concentration may exceed the area of rock crushing that accompanies tectonic disturbances [16]. The territories where underground workings are located are characterized by the formation of zones of geological disturbances of different scales and uneven subsidence of the ground. This leads to the formation of channels and cavities, contributing to radon escaping to the surface. Underground coal mines can substantially shift the radiological parameters of the adjacent part of the lithosphere and other shells [17; 18; 19; 20]. The crustal areas where underground workings are located are characterized by an increased potential for the development of neotectonic processes. It can be assumed that these effects are more intense on the periphery of the excavated underground space. There, as a result of the subsidence of the excavation roof in depth, additional zones of tectonic disturbance under tensile conditions are likely to be formed. In addition, the activation of ancient faults that are located nearby is also possible. These structural changes in the rock can potentially lead to the formation of additional radon transport channels. Such effects even occur in areas composed of weakly radioactive rocks.