Spatial variability and multivariate analysis of natural radioactivity in monazite-bearing coastal soils of Odisha, India

Abstract This study investigates spatial variability in radionuclide distribution and radiological characteristics of coastal soils from Ganjam and Puri, Odisha, India. A total of 72 samples from 24 locations were analyzed using NaI(Tl) gamma-ray spectrometry for 238 U, 232 Th, and 40 K, together with in situ ambient gamma dose measurements. Activity concentrations ranged from 106 to 2139 Bq kg − 1 for 238 U, 275–3825 Bq kg − 1 for 232 Th, and 601–4887 Bq kg − 1 for 40 K, with mean values substantially exceeding global averages and comparable to those reported for major Indian high background natural radiation areas (HBNRAs). Spatial and multivariate analyses revealed pronounced heterogeneity, with localized enrichment consistent with variations in heavy mineral assemblages. No statistically significant difference was observed between Ganjam and Puri ( p > 0.05), indicating broadly comparable radionuclide distributions. The correspondence between radionuclide concentrations and in situ gamma dose rates supports geological and sedimentary controls on the observed radiological characteristics. The mean absorbed gamma dose rate was 1693 ± 134 nGy h − 1 , while the annual effective dose, AGDE, and ELCR were elevated. The external gamma dose was dominated by 232 Th (64.8%), while 238 U and 40 K contributed 29.0% and 6.2%, respectively. These characteristics identify the study area as a coastal high background natural radiation area and provide a regional radiological baseline for the Ganjam–Puri coastal belt.