Evaluation of natural radioactivity in soil, sediment and water samples of Niger Delta (Biseni) flood plain lakes, Nigeria

This paper presents the findings of a baseline study undertaken to evaluate the natural radioactivity levels in soil, sediment and water samples in four flood plain lakes of the Niger Delta using a hyper pure germanium (HPGe) detector. The activity profile of radionuclides shows low activity across the study area. The mean activity level of the natural radionuclides 226Ra, 232Th and 40K is 20 ± 3, 20 ± 3 and 180 ± 50 Bq kg−1, respectively. These values are well within values reported elsewhere in the country and in other countries with similar environments. The study also examined some radiation hazard indices. The mean values obtained are, 76 ± 14 Bq kg−1, 30 ± 5.5 ηGy h−1, 37 ± 6.8 μSv y−1, 0.17 and 0.23 for Radium Equivalent Activity (Raeq), Absorbed Dose Rates (D), Annual Effective Dose Rates (Eff Dose), External Hazard Index (Hex) and Internal Hazard Index (Hin) respectively. All the health hazard indices are well below their recommended limits. The soil and sediments from the study area provide no excessive exposures for inhabitants and can be used as construction materials without posing any significant radiological threat to the population. The water is radiologically safe for domestic and industrial use. The paper recommends further studies to estimate internal and external doses from other suspected radiological sources to the population of the Biseni kingdom.

► The activity profile of the radionuclides has clearly showed the existence of low activity in the study area. ► The average activity concentration of 226Ra, 232Th and 40K is 20 ± 3, 20 ± 3 and 185 ± 47 Bq kg−1 DW (or L−1) respectively. ► These values compared well with other values obtained within Nigeria and other countries of the world. ► The soils and sediments of the area have no immediate health implication on the inhabitants. ► This work has established baseline information for the region.