Assessment of natural radioactivity in soil samples collected from the Tosham region, Northwestern India

This study evaluates the distribution, radiological significance, and controlling factors of naturally occurring radionuclides in agricultural soils from the Tosham Ring Complex (TRC), north-western India, a region underlain by high heat-producing granites of the Malani Igneous Suite. Nineteen soil samples were analyzed using high-purity germanium (HPGe) gamma spectrometry to determine the activity concentrations of 40 K, 226 Ra, and 232 Th. The measured activity concentrations of 40 K ranged from 395.2 to 558.6 Bq kg −1 (mean: 464.0 ± 40.7 Bq kg −1 ), while 226 Ra and 232 Th ranged from 32.8 to 66.4 Bq kg −1 (mean: 45.3 ± 9.3 Bq kg −1 ) and 19.4–38.9 Bq kg −1 (mean: 28.4 ± 5.5 Bq kg −1 ), respectively. The mean activities of 40 K and 226 Ra exceed global average values, whereas 232 Th remains within the worldwide range. Radiological hazard indices, including radium equivalent activity (Raeq), absorbed dose rate (AAD), annual effective dose equivalent (AEDE), annual gonadal equivalent dose (AGED), gamma index (Iγ), and internal and external hazard indices, were calculated to assess potential health risks. Coreelation analysis indicates strong positive correlations between 226 Ra and 232 Th (r ≈ 0.91) and radiological hazard indices (r > 0.95, p < 0.0001), suggesting their contributor to estimate radiological risk. In contrast, 40 K shows comparatively weaker correlations (r = 0.62, p < 0.005). Principal component analysis further confirms that with PC1 ( 226 Ra and 232 Th) 94.94% of total variance and representing a general radioactivity intensity factor. The calculated radiological parameters remain within internationally recommended safety limits, indicating low radiological risk for the studied soils and providing baseline data for natural radioactivity in the region.