Assessment of activity concentration of radionuclides and their transfer factors from the soil to maize plants in Essien Udim Local Government Area of Akwa Ibom State, Nigeria.

Abstract

Maize has been a major source of food consumed by people and animals but evaluation of radiological hazards due to consumption of the maize has not been carried out to ascertain any possible health hazards. At Essien Udim Local Government Area (LGA), the activity concentrations of radionuclides of ⁴⁰K, ²³⁸U and ²³²Th and their transfer factors from soil to maize seeds and stems have been conducted using a gamma ray spectroscopy coupled with NaI detector. A total of 21 samples comprising 7 soil specimens, 7 maize seeds and 7 maize stems were collected and analysed. The mean activity concentrations of the radionuclides in the soil, maize seeds and maize stems samples are respectively 433.24 ± 5.65 Bq/kg, 367.61 ± 6.19 Bq/kg, 603.11 ± 8.04 Bq/kg for ⁴⁰K, 12.66 ± 0.07 Bq/kg, 10.06 ± 0.06 Bq/kg, 39.94 ± 0.07 Bq/kg for ²³⁸U and 3.07 ± 0.07 Bq/kg, 1.85 ± 0.06 Bq/kg, 3.03 ± 0.09 Bq/kg for ²³²Th. Most of these obtained values are within the safety limits except for some values of ⁴⁰K and ²³⁸U in maize stems which exceeded their safety limits. The mean of transfer factors of the radionuclides for the maize seeds and stems were 0.9858 and 1.5411 for ⁴⁰K, 1.0841 and 3.4970 for ²³⁸U, 0.6768 and 1.1811 for ²³²Th radionuclides. The transfer factors are higher in maize stems than seeds and in some cases, exceeded unity which is the safety recommended limit. The mean annual ingestion dose due to the consumption of the maize seeds is 0.3824 mSv/yr for adults and 0.2375 mSv/yr for children. These results show that maize consumption does not pose a radiological health hazard to the consumers of maize from the study area.