Variation of primordial radionuclide activities in the drinking water collected from Darbandikhan Lake water resources during four seasons

The variation in the levels of natural radioactive materials in drinking water throughout the four seasons has been studied in Darbandikhan Lake using a gamma spectrometer system with an HPGe detector for the measurements. The arithmetic activity concentrations for ²²⁶Ra, ²³²Th and ⁴⁰K in the water samples were established to be 1.54 ± 0.21, 2.39 ± 0.0.33 and 77.94 ± 1.70 Bq/L; 1.22 ± 0.18, 2.38 ± 0.31 and 63.79 ± 1.48 Bq/L; 1.18 ± 0.18, 1.89 ± 0.30 and 51.30 ± 1.33 Bq/L; 1.34 ± 0.20, 2.30 ± 0.32 and 68.14 ± 1.56 Bq/L, for spring, summer, autumn, and winter, respectively. It was observed that ²³²Th was about twice as high as the WHO’s recommended levels for drinking water. In wet seasons of spring and winter, Drinking water show higher average activity concentration than those in summer and autumn. The results obtained from ANOVA statistical tests showed that only ⁴⁰K had a statistically significant difference in concentration throughout the four seasons (p = 0.029). Both the external and internal hazard indices (0.025 and 0.03) are significantly below the recommended value of one. The committed effective dose is measured at 0.70 mSv/y, while the annual effective doses for outdoor and indoor exposure are 0.006 mSv/y and 0.043 mSv/y, respectively. The calculated excess lifetime cancer risk due to water ingestion is 2.46 × 10⁻³, whereas the cancer risk for indoor and outdoor exposure is 0.02 × 10⁻³ and 0.15 × 10⁻³, respectively. With the exception of the annual committed effective dose and the cancer risk associated with water consumption, all hazard indices are significantly below the recommended global standards.