Radioactivity concentrations in anthill soils used for building construction: A case study of Oshikoto region, Namibia

Abstract

The level of background radioactivity concentration is gradually increasing worldwide due to anthropogenic activities. Humans are exposed to radiation either from terrestrial sources emanating from these activities or cosmological sources. The main aim of the study was to measure the radioactivity concentrations in anthill soils used for building residential dwellings in the northern region. The study was conducted along the B1 road of the Oshikoto region to determine the natural activity concentration of terrestrial radionuclides of ²³⁸U (²²⁶Ra), ²³²Th and ⁴⁰K by using a high-purity germanium detector and to assess the radiological health parameters associated with the anthill building material. The average activity concentrations for (²²⁶Ra), ²³²Th and ⁴⁰K were found to be 8.01 ± 0.43, 11.75 ± 0.48 and 159.33 ± 5.19 Bq/kg, respectively. All measured average activity concentrations of the radionuclides were below the world safety limits. The corresponding radiological parameters of interest of the study (absorbed dose rate, annual effective dose equivalence, radium activity, external hazard index, and internal hazard index) were estimated. The averages for the absorbed dose rate and annual effective dose equivalent were found to be 17.02 ± 0.42 nGy/h and 0.02 ± 0.00 mSv/y, respectively, whilst the averages for radium equivalent activity, external hazard index and internal hazard index were 36.08 ± 0.92 Bq/kg, 0.10 ± 0.00 and 0.12 ± 0.00, respectively. The absorbed dose rate for soil was approximately three times (x3) lower than that of the world average. The spread of data from the mean value was 5.94 nGy/h for the absorbed dose rate, 6.29 mSv/y for annual effective dose, 11.02 Bq/kg for radium equivalent activity, 0.03 for the external hazard index and 0.04 for the internal hazard index. The average values for the external and internal hazard indices were below unity, implying that the external exposure of humans to radiation is negligible and therefore, the soil materials are safe for building constructions of human shelters