Natural radioactivity is one of the essential components of the environment. Unlike the Sudety mountains area in Poland, the Tatra Mountains were not the subject of wide survey as regards the levels of natural radioactivity. Especially, the concentrations of radon (natural radioactive gas) have not been investigated there in terms of their possible negative health impact. Within the frame of bilateral cooperation between the Institute of Nuclear Physics in Kraków, Poland, and the Jožef Stefan Institute in Ljubljana, Slovenia, the measurements of natural radioactive elements in old uranium mines in the Tatra National Park were performed in June 2010. The investigated sites were located in Dolina Białego (The Valley of the White). One of the mines is situated near the tourist path. The paper presents the results of complex measurements of natural radioactivity in both uranium drifts. The concentration of radon gas inside the mining drifts exceeded 28,000 Bq m(-3). Also, very high gamma dose rates were observed (up to 5600 nSv h(-1)). The maximum concentrations of natural radioactive elements (potassium (40)K, radium (226)Ra, thorium (232)Th) in rock samples amounted to 535, 2137, and 18 Bq kg(-1), respectively. The effective dose rates due to radon and thoron inhalation have been assessed as 0.013 mSv h(-1) (for the lowest concentration) and 0.121 mSv h(-1) (for the highest concentration).

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Zn1-xMgxO nanocomposites were synthesized by a modified sol-gel method. The effect of increasing Mg content on structural, optical properties, and antibacterial activity was studied. The structure and physical properties of the Zn1-xMgxO nanocomposites were characterized by thermogravimetric (TG) analysis, Fourier-transform infrared spectroscopy (FT-IR), X-Ray Diffraction (XRD), and transmission electron microscope (TEM). The optical properties were investigated by UV-visible spectroscopy and Photo luminesce spectra (PL). The thermal properties and the weight stability were studied for the samples using TG-Analysis to determine the best annealing temperature at 550 °C. The XRD result confirms that clear indications for segregation into a hexagonal and a cubic phase are found for samples having magnesium content between 0.2 ≤ x ≤ 0.8. According to Scherer's formula, the average particle size of the synthesized nanocomposites is in the range of 16.32-25.56 nm. TEM images showed hexagonal, irregular, and spherical shapes. The calculated band gap energies (Eg) of the Zn1-xMgxO nanocomposites were changed from 3.18 to 3.31 eV by increasing Mg concentration in the Zn1-xMgxO nanocomposites. The XRD and UV-vis analysis results indicated that the physical characteristics of Zn1-xMgxO nanocomposites were dependent on increasing the incorporation of Mg2+ ion concentration. The antibacterial assessment illustrated that the ZnO-MgO nanocomposites showed excellent antibacterial activity, the inhibition zoon increases from 12 mm for pure ZnO to 15 mm for Zn1-xMgxO nanocomposites with Mg ratio (x=0.4). The result concluded that Zn1-xMgxO nanocomposites have significant potential for antibacterial applications.