Transfer factors of 40k, 232th and 238u from soil to cassava system from farmlands in selected parts of Akwa Ibom State, Nigeria.

Abstract

Naturally occurring radionuclide materials are known to exist in soils and can be transferred into plants and edible tubers like cassava which eventually gets into the food chain. This work was aimed at estimation of transfer factors of ⁴⁰K, ²³²Th and ²³⁸U in the soil to cassava-selected farmlands in Abak, Ikot Ekpene, Ukanafun and Etim Ekpo Local Government areas (LGA). The activity concentrations of twenty (20) soil samples and 15 Cassava samples from the farmlands were determined using gamma spectrometry. Measured mean activity concentrations of ⁴⁰K, ²³²Th and ²³⁸U in Abak soil samples were 475.74 ± 8.38 Bq/Kg), 57.21 ±0.98 Bq/Kg and 18.29 ± 0.35 (Bq/Kg). Ikot Ekpene soils were 539. 94 ± 8.35 (Bq/Kg), 62.28 ± 1.02 (Bq/Kg) and 17.84 ± 0.30 (Bq/Kg) respectively. Measured mean activity concentration for ⁴⁰K, ²³²Th, and ²³⁸U in Ukanafun soils were 485.46 ± 8. 62 Bq/Kg), 47.15 ±0.89 Bq/Kg, and 16.78 ± 0.28 (Bq/Kg). Etim Ekpo soils had mean activity concentrations of 431. 95 ± 8.20 (Bq/Kg), 51.00 ± 0.94 (Bqkg-1) and 16.67 ± 0.29 (Bq/Kg) respectively. Measured mean activity concentration for ⁴⁰K, ²³²Th, and ²³⁸U in Abak cassava were 593.94 ± 9.36 Bq/Kg), 19.29 ± 0.56 Bq/Kg and 17.09 ± 0.30 (Bq/Kg). Ikot Ekpene cassava shows mean activity concentrations of ⁴⁰K, ²³²Th, and ²³⁸U measured were 637.72 ±9.72 (Bq/Kg), 17. 79 ± 0.54 (Bq/Kg) and 18.19 ± 0.31 (Bq/Kg) respectively. Measured mean activity concentration for ⁴⁰K, ²³²Th and ²³⁸U in Ukanafun cassava samples were 614.55 ± 9.41 Bq/Kg), 22.27 ±0.62 Bq/Kg, and 15.19 ± 0.28 (Bq/Kg). Cassava in Etim Ekpo had mean activity concentrations of ⁴⁰K, ²³²Th and ²³⁸U of 581. 21 ± 10.06 (Bq/Kg), 21.08 ± 0.24 (Bq/Kg) and 16.36 ± 0.58 (Bq/Kg) respectively. The estimated transfer factors for ⁴⁰K were 1.28, 1.20, 1.39, and 1.35 respectively for Abak, Ikot Ekpene, Ukanafun, and Etim Ekpo. The mean transfer factor values for 232Th were 0.36, 0.30, 0.49 and 0.43 while the mean transfer factor for ²³⁸U was 0.93, 1.04, 0.91 and 1.08. The TF values for ⁴⁰K obtained for this work were higher than the recommended safe value of unity, while TF values for ²³²Th and ²³⁸U obtained for this work were very low. The variation in TF may be as a result of the geological properties of the area and the difference in the mobility rate of different radionuclides. However negligible the contamination is, the potential health risk could be minimised when food is cooked before being consumed.