Assessment of the Natural Radioactivity of Polish and Foreign Granites Used for Road and Lapidary Constructions in Poland
The measurements of the specific activity of natural radioactive isotopes of radium (226Ra), thorium (232Th) and potassium (40K) in chosen samples of imported (China, Finland, Spain, India, Sweden) and Polish (Izerski, Karkonosze, Siedlimowicki, Strzegomski, Strzelinski) granites were performed. The measurements were carried out with 2 × 2” NaI(Tl) scintillation detector. The measured specific activity on natural radioactive isotopes were within the following ranges: 5.8–312 [Bq kg−1], 5.5–189 [Bq kg−1] and 109–1590 [Bq kg−1] for 226Ra, 232Th and 40K, respectively. Obtained concentrations of radioactive isotopes allowed to perform the analysis of the exposure of the humans from the ionizing radiation emitted by the granites. The determination of the exposure consisted in the calculation of absorbed gamma dose rate (D) [nGy h−1] for each sample, which fell in the range between 20 and 511 [nGy h−1], annual effective dose rate (AED) [mSv year−1] ranging between 0.10 and 2.50 [mSv year−1], radium equivalent activity (Raeq) [Bq kg−1] with values between 22 and 570 [Bq kg−1], external and internal hazard indices (Hex) and (Hin) falling in the ranges 0.06−1.53 and 0.08–2.41 respectively, as well as gamma (Iγ) and alpha (Iα), representative level indices with values 0.08–2.0 and 0.029–1.56, respectively. Moreover, obtained results were compared with the international standard values given by the European Commission (EC), the United Nations Scientific Committee on the Effects of Atomic Radiation given in UNSCEAR Reports, and the results of research from other laboratories.