This study presents the first comprehensive spatial analysis of naturally occurring radioactive material (NORM) activity concentrations and absorbed dose rates across Bangladesh. Utilizing a database compiled from 56 published studies and 40 unpublished theses (1990-present), environmental sample data were mapped onto a systematic grid system comprising 2,094 cells (8.05 km × 8.05 km). Ordinary Kriging interpolation was applied to visualize nationwide distributions. The analysis revealed significant spatial heterogeneity primarily driven by differences in geology, rock structures, and soil types. Activity concentrations of Ra-226, Th-232, and K-40 ranged from 0.01 to 647.5 Bq/kg, 0.2 to 1230.0 Bq/kg, and 0.04 to 2352.0 Bq/kg, respectively. Consequently, the absorbed dose rates varied widely from 0.02 to 745.86 nGy/h, yielding a national average of 64.16 nGy/h. Furthermore, the gridded mapping exposed severe sampling imbalances: while some localized regions were measured up to 13 times, vast areas remain entirely unsampled. By establishing this pre-operational national baseline, this study successfully distinguishes natural background levels from potential Technologically Enhanced NORM (TENORM). The findings provide a critical reference for ongoing environmental monitoring particularly to assess radiation levels around the soon-to-be-operational Rooppur Nuclear Power Plant (RNPP) and offer a strategic framework to guide future targeted sampling in unmeasured regions.
Anik et al. (Wed,) studied this question.