Variability of 137Cs and natural radionuclides accumulation in mosses relative to soil activity in Iğdır, Türkiye

Introduction This study investigates the activity concentrations of 232 Th, 226 Ra, 40 K, and 137 Cs in soil and moss samples collected from locations in Iğdır Province, Türkiye to evaluate spatial patterns and radionuclide accumulation behavior. Methods High-purity germanium (HPGe) gamma spectrometry was used to quantify radionuclide activities. Results Statistical analyses included Shapiro–Wilk normality testing, descriptive comparisons between soil and moss, and correlation assessments. Concentration ratios (CR = A moss /A soil ) were calculated to evaluate radionuclide accumulation patterns across species and sites. Spatial variability and multivariate structure were examined using PCA and k-means clustering to identify site- and nuclide-driven grouping patterns. Key radiological parameters calculated for the health risk analysis included absorbed gamma dose rate, internal and external hazard indices, radium equivalent activity, and annual effective dose equivalent. In moss samples, the mean activity concentrations of 226 Ra, 232 Th, 40 K and 137 Cs were measured as 13.74 ± 0.83 Bq kg -1 , 13.79 ± 1.1 Bq kg -1 , 244.72 ± 7.6 Bq kg -1 , 129.47 ± 1.74 Bq kg -1 , respectively, and in soil samples, 23.74 ± 0.82 Bq kg -1 , 22.53 ± 1.11 Bq kg -1 , 427.01 ± 8.95 Bq kg -1 , 215.74 ± 1.83 Bq kg -1 , respectively. Discussion All calculated radiological hazard indices, derived from natural radionuclide concentrations, were within permissible recommended limits. Slightly elevated annual effective dose values and absorbed gamma dose rates are observed for the total activity concentrations of both anthropogenic and natural radionuclides, exceeding world population-weighted outdoor averages.