Asian Journal of Physical and Chemical Sciences

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.