Natural radioactivity and GIS mapping of soils in Binh Phuoc, Vietnam

This study investigates the natural radioactivity in 500 soil samples collected across Binh Phuoc Province, Vietnam, a region characterized by basalt formations and bauxite mining. Activity concentrations of ²²⁶Ra, ²³²Th, ⁴⁰K, and ¹³⁷Cs were measured using gamma spectrometry, with spatial distributions mapped at a 1:60,000 scale using a QGIS software. Results revealed ²²⁶Ra ranging from 5.88 to 63.17 Bq.kg^-1, ²³²Th from 17.78 to 117.33 Bq.kg^-1, ⁴⁰K from 111.42 to 1019.90 Bq/kg, and negligible ¹³⁷Cs of about 0.26 Bq.kg^-1. Radiological hazard indices, including radium equivalent activity (Ra_eq: 117.42 Bq.kg^-1) and external hazard index (Hex: 0.317), remained below international thresholds of 370 Bq.kg^-1 and 1, respectively, indicating low environmental risk. Driven by a high sampling density (approximately 1 sample per 14 km²), the detailed geographic information systems (GIS) maps provide the first high-resolution baseline for naturally occurring radioactive materials (NORM) monitoring and support bauxite mining management as well as agricultural safety assessments in southeastern Vietnam. This research contributes significant data to the limited literature on natural radioactivity in Southeast Asian soils.