Assessment of Natural Radioactivity, Radiological Hazards and Spatial Variability of Coastal Sediments in Akwa Ibom State, Nigeria
DOI:
https://doi.org/10.83080/rejost.vol6no5.305Keywords:
Natural radioactivity, Activity concentration, Sediments, Radiological hazard, Niger Delta, Gamma spectrometryAbstract
The present research work investigated the concentrations of natural radionuclides (⁴⁰K, ²³⁸U, and ²³²Th) and their associated radiological hazards in sediment samples taken from Etiza (Eastern Obolo (EO)), Okorotak (Ibeno), and Enwang (Mbo) regions of Niger Delta coastline, Nigeria. Gamma-ray spectrometry was employed to determine the concentration levels of twenty-nine sediment samples, whereas radiological hazard parameters, namely radium equivalent activity (Ra(eq)), absorbed dose rate (D), annual effective dose equivalent (AEDE), and excess lifetime cancer risk (ELCR), were calculated based on international guidelines. Various statistical methods including descriptive statistics, Shapiro –Wilk test of normality, Levene's test, one-way ANOVA, Kruskal-Walli’s test, and Tukey’s HSD test were applied to analyze the spatial variations. The mean activity concentrations varied between 180.04 – 463.83 Bq kg⁻¹ for ⁴⁰K, 3.67 – 8.43 Bq kg⁻¹ for ²³⁸U and 48.57-74.81 Bq kg⁻¹ for 232Th. The ²³⁸U levels were still lower than the world average level but the 232Th levels were found to be higher than the world reference value, which indicated that there was an enrichment of thorium due to geological reasons in the area. Significant spatial variation occurred only for ⁴⁰K (p < 0.05), with Ibeno showing higher levels. All the mean Raeq values (86.99-151.13 Bq kg⁻¹), absorbed dose rate (38.54-68.42 nGy h⁻¹), AEDE (0.059-0.10 mSv y⁻¹) and ELCR (0.16-0.29 × 10⁻³) fell within internationally accepted safety guidelines. These results suggest that there is no threat to human health and provide useful baseline data for the Niger Delta coast. The calculated radiological indices were below internationally recommended safety limits, indicating that the sediments presently pose insignificant radiological risks to residents and aquatic ecosystems.
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