Assessment of the Natural Radioactivity in the Brazilian State of Rio Grande Do Norte

TLDR

The study sampled 51 soil cores to 30 cm depth across central and eastern Rio Grande do Norte and measured background radionuclide concentrations with an HPGe gamma‑ray spectrometer, supplemented by hand‑held scintillometer surveys of external gamma radiation in Santana do Matos. Average soil activities were 29 ± 19.4 Bq kg⁻¹ for ²²⁶Ra, 46.6 ± 36.2 Bq kg⁻¹ for ²³²Th, and 677.8 ± 434.9 Bq kg⁻¹ for ⁴⁰K, with Santana do Matos bedrock exhibiting markedly higher levels (≈90 Bq kg⁻¹ ²²⁶Ra, 285.6 Bq kg⁻¹ ²³²Th, 1,414 Bq kg⁻¹ ⁴⁰K) and surrounding areas showing even higher external gamma doses.

Abstract

Fifty-one soil samples were collected to a depth of 30 cm in the central and eastern region of the Brazilian state of Rio Grande do Norte. Concentrations of background radionuclides in soil samples were determined by gamma ray spectrometry with an HPGe detector. The average concentrations of 226Ra, 232Th, and 40K in the surveyed soils were 29.0 ± 19.4 Bq kg−1, 46.6 ± 36.2 Bq kg−1, and 677.8 ± 434.9 Bq kg−1, respectively. The bedrock of Santana do Matos (Rio Grande do Norte) showed fairly high radioactivity (90 Bq kg−1 of 226Ra, 285.6 Bq kg−1 of 232Th, and 1,414 Bq kg−1 of 40K). Radiological measurements carried out in Santana do Matos with a hand-held scintillometer revealed external gamma radiation ranging from 200–330 nGy h−1 in the downtown area. Higher values were recorded in the surroundings of that town.