Distribution of naturally occurring radionuclides and associated radiological hazards in south-western Nigeria coastal and off-shore sediment, Gulf of Guinea

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发表日期：

2026年3月6日

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Samuel Olatunde Popoola,
Ayoola Olubunmi Nubi,
Olaniyi Rafiu Shelle,
Ismail Adejare Ladigbolu,
Oluwaseun Adedayo Adeleye,
Olaiwola Falilu Adekunbi,
Otolorin Opeyemi Oyatola,
Elizabeth Ekene Nwamba,
Ismaila Ayinde Oba,
Taofeek Olawale Olabiyi,
Olaoluwa Akintoye Fashade

摘要

The concentrations of natural radionuclides in the sediments along the Lagos coast and the Gulf of Guinea in South-western Nigeria were measured using gamma-ray spectrometry. The mean activity concentrations of ⁴⁰ K, ²³⁸U, and ²³²Th were found to vary, with values of 240.36 ± 129.90 Bqkg⁻¹, 6.20 ± 1.08 Bqkg⁻¹, and 4.26 ± 1.40 Bqkg⁻¹ at the Lagos coast, and 432.50 ± 68.18 Bqkg⁻¹, 10.76 ± 2.96 Bqkg⁻¹, and 3.85 ± 1.82 Bqkg⁻¹ at the Gulf of Guinea coast, respectively. The overall calculated mean of the indoor absorbed dose rates was 17.58 ± 5.66 nGyh⁻¹, with a corresponding total annual effective dose of 0.11 ± 0.03 mSvy⁻¹. To assess the radiological hazards associated with the presence of naturally occurring radioactive materials (NORM) in sediments, we calculated the representative level index (RLI), radium equivalent activity (Raeq), external hazard index (Hex), excess lifetime cancer risk (ELCR), and internal hazard index (Hin). These indices provide a way to evaluate potential health risks to humans, benthic ecosystems, and the marine environment. The overall estimated values for Raeq, Hex, Hin, RLI, and ELCR were 31.10 ± 12.32 Bqkg⁻¹, 0.08 ± 0.03, 0.10 ± 0.04, 0.28 ± 0.09, and 0.07 ± 0.03 × 10^–3, respectively. Principal Component Analysis (PCA) was used to link radionuclide distributions to sediment’s particle size, and results reveal close association between sand and silt with elevated ²³²Th; and clay with enriched ⁴⁰ K and ²³⁸U concentrations respectively. The sediment values from the Lagos coast and the Gulf of Guinea fell below the safety limits set by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) (e.g., 400Bqkg⁻¹, 30Bqkg⁻¹ and 35Bqkg⁻¹), except at few stations that showed elevated ⁴⁰ K due to local geology. The values obtained for the hazard indices in sediment from the study area were similar to those found in other areas recognized for their low radiation levels. Therefore, it can be concluded that sediments from the Lagos coasts and Gulf of Guinea basins pose minimal potential health risks to humans, benthic ecosystems, and the environment, complying with established guidelines and regulations for permissible radiation exposure. The results of this study could serve as an important baseline for future epidemiological studies and monitoring initiatives in the region.