## 2 Materials and Methods
### Sample Preparation and Measurements of Gamma Spectrometry  
The activity concentrations of radionuclides, such as radium-226, thorium-232, potassium-40, and cesium-137, used in this study were obtained from the Environmental Radiation Atlas of Turkive, prepared by the Turkish Atomic Energy Authority (TAEK) [24]. This report provides a geographical mapping of the natural radioactivity levels in Mardin Province (including its districts) but does not include radiological parameter calculations. The use of TAEK data in this study is based on its reliability, standardized measurement methods, and national acceptance, ensuring consistency with previous research conducted in other regions of Turkiye. The primary reason for using the existing data provided by TAEK in our study is to analyze regional radiological risks based on a dataset consisting of long-term, reliable measurements. These data have been collected using standard methods and are recognized as reliable at the national level. In our study, we re-mapped the natural radioactivity levels using equal activity distribution curves for each radionuclide and performed radiological parameter calculations. Additionally, the spatial distributions of these calculated radiological parameters were presented to offer a more comprehensive assessment. According to the TAEK report [24], 23 surface soil samples were collected from Mardin Province. It was stated that the sampling locations were selected to best represent the region, prioritizing areas with good water permeability that were not affected by flooding or excessive rainfall, were free from vegetation or leaf cover, and were located in open, undisturbed, flat areas. The report further specifies that soil samples were collected from an area of approximately 1 m\({}^{2}\) at a depth of 0-5 cm, with at least three subsamples mixed to create a composite sample. Before analysis, the samples were cleaned of foreign materials, such as stones, plant roots, and other debris. The activity concentrations of the soil samples were analyzed using a High-Purity Germanium (HPGe) detector (Canberra Inc., Meriden, CT, USA) at TAEK's [24] research and training centers in Ankara (SANAEM)  
Figure 2: The location of the Mardin Province [23; 24] (combined and modified).  
and Istanbul (CNAEM). The minimum detectable activities (MDAs) of the detector in use were determined using Equation (1), as outlined in similar reports.  
\[\text{MDA}=\frac{2.71+4.65\sqrt{\text{B}}}{\left(\varepsilon\ \times\ \text{t}\ \times\ \gamma\ \times\ \text{m}\right)} \tag{1}\]  
where B is the background counts, \(\varepsilon\) is counting efficiency, \(\gamma\) is the gamma emission probability for the gamma of interest, m is the sample mass, and t is the measurement time.  
In this TAEK report [24], the soil sample analysis method was described as follows: The samples of soils were first dried in the air at room temperature, then crushed, and after a homogenization process, they were sieved through a 30 mesh BS (0.5 mm mesh). A total of 1 kg of the sieved samples was further dried at 110 \({}^{\circ}\)C for 24 h for removal of moisture and then subsequently cooled in a dry ambient area. The prepared samples were kept in 250 cm\({}^{3}\) polystyrene bottles, which were hermetically sealed and left undisturbed for 4 weeks to achieve secular equilibrium. This equilibrium ensures that the decay rate of radon progeny becomes equal to that of the parent isotope, which is a critical stage to confine radon gas in the sample volume, and retain its progeny in the material [24].