Spatial distribution and soil-to-plant transfer factors of radionuclides in agricultural soil around the Barapukuria coal mining site, Bangladesh

In order to investigate the level of radioactivity and translocation of radionuclides from soil to plants, fifteen agricultural soil and fifteen edible plant samples grown in soils were collected from Barapukuria coal mining area, Bangladesh. The physicochemical properties (pH, EC, %OC, %OM, %N, %P, and N/P) were evaluated and the XRD patterns of soil samples were obtained. The gamma activity of ²³⁸U, ²³²Th, and ⁴⁰K in soil and plant samples was analyzed by gamma-ray spectroscopy with an HPGe detector. The activity concentrations in soil samples varied in the order of ⁴⁰K > ²³⁸U > ²³²Th. The gross alpha and gross beta activity were also measured by using a ZnS(Ag) scintillation counter. The average gross alpha and gross beta activity in soil and plant samples were found to be 119 ± 4 Bq kg^-1 and 384 ± 17 Bq kg^-1, and 35.49 ± 1.94 Bq kg^-1 and 249 ± 10 Bq kg^-1, respectively. The calculated mean transfer factors (TFs) for ²³⁸U, ²³²Th, and ⁴⁰K were 0.21, 0.20 and 0.32, respectively. Spinach (<i>Amaranthus lividus</i>) had the highest uptake of ²³⁸U (TF value of 0.30), while cauliflower (<i>Brassica oleracea</i>) showed the greatest (TF value of 0.08). Nonetheless, in the cases of ²³²Th and ⁴⁰K, the highest TFs were observed for malabar spinach (<i>Basella alba</i>) (TF value of 0.31) and green pea leaf (<i>Pisum sativum</i>) (TF value of 0.45). According to the radiation hazard assessment, the levels were often lower than the UNSCEAR world-average values. The contamination factor (CF) indicates that the soil samples were moderately contaminated by ²³⁸U. Correlation analysis revealed that ²³²Th was mostly responsible for radiation health hazards, whereas for plant samples, ⁴⁰K was responsible for the internal hazard index.