Radiological Assessments of Farm Soil and Yam Tubers Grown in Ika North East Local Government Area of Delta State, Nigeria

Résumé fourni par la source

40K, 238U and 232Th are natural radionuclides found in soil and may migrate into plants through their root. Yam is a food crop that is commonly produced and widely ingested in the study area. Therefore, it is important to assess the concentration levels of soil and yam radionuclides in order to evaluate the associated radiological risk factors. This study evaluated the activity concentration, transfer factor, and radiological risk associated with natural radionuclides in farm soils and yam tubers cultivated in Ika North East Local Government Area, Delta State, Nigeria. Ten soil and ten yam samples were collected from selected farms and analyzed using a NaI(Tl) gamma-ray spectrometry system. The activity concentrations of 40K, 238U and 232Th were determined along with the estimation of transfer factors (TFs), absorbed dose rate, annual effective dose, ingestion dose, and excess lifetime cancer risk (ELCR) associated with studied samples. The mean activity concentrations in soil were 353.75 ± 4.43, 4.01 ± 0.08, and 1.95± 0.05 Bq kg⁻¹ for 40K, 238U, and 232Th, respectively, while the corresponding mean values in the yam sample were 366.04 ± 4.38, 4.57 ± 0.07, and 1.64 ± 0.05 Bq kg⁻¹. The radionuclide concentrations is in order of 40K >238U>232Th in both soil and yam samples. Mean transfer factors were 1.05, 1.20, and 0.96 for 40K, 238U, and 232Th, respectively, indicating appreciable soil-to-yam transfer. The mean absorbed dose rate and outdoor annual effective dose were 19.38 nGy h⁻¹ and 21.42 μSv y⁻¹, respectively, both were below the recommended global averages. The mean annual ingestion dose from yam consumption was 0.21 mSv y⁻¹, which is below the public dose limit of 1 mSv y⁻¹. However, the mean excess lifetime cancer risk was 1.38 × 10⁻³, which is higher than the recommended value of 0.29 × 10⁻³. The study concludes that although most of the current external and ingestion radiation doses are within acceptable limits, continuous monitoring of radionuclide levels in yam and agricultural soils is necessary to minimize potential long-term radiological health risks.

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