Evaluation of Radiological Hazard Indices in Selected Farmland Soils around Landfill Sites in Rivers State, Nigeria

Abstract

Natural radionuclide levels and radiological hazard indices in soils from selected farmlands around landfills in Rivers State, Nigeria, were assessed using gamma-ray spectroscopy with a NaI (Ti) detector. The assessment considered 40K, 238U and 232Th at the Aluu, IAUE and Igwuruta dumpsites. For Aluu, the calculated radium equivalent activity (Raeq) values in the present study ranged from 9.10 to 135.49 Bq/kg, with an average value of 62.24 ± 14.60 Bq/kg. The Iγ values ranged from 0.04 to 0.51, with a mean of 0.25 ± 0.06; Hₑₓ values ranged from 0.02 to 0.37, with a mean of 0.16 ± 0.04; and Hᵢₙ values ranged from 0.03 to 0.42, with an average of 0.22 ± 0.05. The absorbed dose rate ranged from 3.96 to 58.59 nGy/h, with a mean of 28.02 ± 6.31 nGy/h, while the AEDE values ranged from 0.00 to 0.07 mSv/y, with a mean of 0.03 ± 0.001 mSv/y. The gonadal dose ranged from 27.08 to 405.02 mSv/y. The ELCR values ranged from 0.08 × 10⁻³ to 1.12 × 10⁻³, with a mean of 0.48 ± 0.13 × 10⁻³, while the AUI values ranged from 0.08 to 1.12, with an average of 0.48 ± 0.13. For IAUE, the Raeq values ranged from 21.47 to 112.64 Bq/kg, with a mean of 85.60 Bq/kg. The Iγ values ranged from 0.09 to 0.49, with a mean of 0.37 ± 0.04; Hₑₓ values ranged from 0.06 to 0.30, with an average of 0.23 ± 0.03; and Hᵢₙ values ranged from 0.06 to 0.48, with a mean of 0.34 ± 0.04. The absorbed dose rate ranged from 11.13 to 50.39 nGy/h, with an average of 39.00 ± 4.18 nGy/h, while the AEDE values ranged from 0.01 to 0.06 mSv/y, with a mean of 0.05 ± 0.006 mSv/y. The gonadal dose ranged from 82.73 to 345.36 mSv/y, with a mean of 267.79 ± 27.82 mSv/y. The ELCR values ranged from 0.05 × 10⁻³ to 0.22 × 10⁻³, with a mean of 0.17 ± 0.02 × 10⁻³, while the AUI values ranged from 0.05 to 0.98, with an average of 0.70 ± 0.10. For Igwuruta, the calculated Raeq values ranged from 15.67 to 104.85 Bq/kg, with an average value of 54.13 ± 10.58 Bq/kg. The Iγ values ranged from 0.06 to 0.48, with a mean of 0.24 ± 0.05; Hₑₓ values ranged from 0.04 to 0.28, with an average of 0.15 ± 0.03; and Hᵢₙ values ranged from 0.04 to 0.47, with a mean value of 0.22 ± 0.05. The absorbed dose rate ranged from 7.17 to 47.90 nGy/h, with a mean of 25.23 ± 4.82 nGy/h, while the AEDE values ranged from 0.01 to 0.06 mSv/y, with a mean of 0.03 ± 0.006 mSv/y. The gonadal dose ranged from 51.14 to 326.57 mSv/y, with a mean of 175.00 ± 32.44 mSv/y. The ELCR values ranged from 0.10 × 10⁻³ to 0.21 × 10⁻³, with a mean of 0.11 ± 0.07 × 10⁻³, while the AUI values ranged from 0.10 to 0.89, with a mean of 0.40 ± 0.10. The radiological parameters varied among the three locations. IAUE recorded the highest mean values of Raeq (85.60 Bq/kg), Iγ (0.37), Hₑₓ (0.23), Hᵢₙ (0.34), absorbed dose rate (39.00 nGy/h), AEDE (0.05 mSv/y), gonadal dose (267.79 mSv/y) and AUI (0.70), indicating comparatively higher radiological activity. Igwuruta recorded the lowest values for most parameters, including Raeq (54.13 Bq/kg), absorbed dose rate (25.23 nGy/h), Hₑₓ (0.15) and AUI (0.40). In contrast, Aluu recorded the highest mean ELCR (0.48 × 10⁻³), compared with 0.17 × 10⁻³ at IAUE and 0.11 × 10⁻³ at Igwuruta, indicating a comparatively higher estimated lifetime cancer risk at Aluu. Overall, all three locations showed radiological indices generally below their respective recommended reference limits, suggesting a low overall radiological hazard, although Aluu warrants attention because of its relatively elevated ELCR. However, the Aluu site recorded the highest value of ELCR (0.48 × 10⁻³), suggesting a comparatively greater potential lifetime cancer risk. In summary, the findings indicate that the investigated soils do not pose a significant radiological threat under present conditions, although regular radiological monitoring and improved landfill management are recommended, especially at the Aluu dumpsite.