A review of 137Cs and 40K soil-to-plant transfer factors in tropical plants

Study of soil-to-plant transfer factors (TFs) of 226Ra, 232Th, and 40K on plants cultivated on ex-tin mining land in Bangka Belitung, Indonesia

Soil-to-plant transfer factors (TFs) are of fundamental importance in measuring the environmental impact due to the presence of radioactivity in soil and agricultural crops. The present study thus to measure soil-to-plant TFs of ²²⁶Ra, ²³²Th, and ⁴⁰K on horticultural plants cultivated on ex-tin mining land in Bangka Belitung islands. There were 21 samples of 15 species and 13 families from 17 locations comprising four vegetables species, five fruits species, three staple foods species, and three others. The TFs were measured in leaves, fruit, cereal, kernel, shoot, or rhizome. The results showed that ²³⁸U and ¹³⁷Cs were almost not found in plants, whereas ²²⁶Ra, ²³²Th, and ⁴⁰K were measured. In soursop leaf, common pepper leaf, and cassava peel, on ²²⁶Ra, the TFs for the non-edible parts, (0.42 ± 0.02; 1.05 ± 0.17; 0.32 ± 0.01 respectively) were significantly higher than soursop fruit, common pepper seed, and cassava root for the edible parts (0.01 ± 0.005; 0.29 ± 0.09; 0.04 ± 0.02 respectively).

Soil to tobacco component transfer factors for natural radionuclides 40K, 226Ra, and 232Th and the risk assessment of tobacco leaf in smoking

This study determined the activity concentrations and corresponding transfer factors (TF) of ⁴⁰K, ²²⁶Ra, and ²³²Th in three tobacco components (root, stem, and leaf). The radiation hazard index parameters were assessed for the tobacco leaf. The activity concentrations in the soil were 589-762, 32-43, and 49-59 Bq kg-dw^-1 (dry weight) for ⁴⁰K, ²²⁶Ra, and ²³²Th, respectively. The average activity concentrations of ⁴⁰K, ²²⁶Ra, and ²³²Th were 447, 5.41 and 5.69 Bq/kg-dw for the root, 670, 9.64 and 7.61 Bq kg-dw^-1 for the stem, and 793, 6.79 and 6.15 Bq kg-dw^-1 for the leaf, respectively. The TF values were 0.42-1.42, 0.10-0.49 and 0.06-0.23 for ⁴⁰K, ²²⁶Ra, and ²³²Th, respectively. The stem and leaf ⁴⁰K TF values were significantly higher than the root values. The stem ²²⁶Ra TF values were significantly higher than the root values. The ²²⁶Ra and ²³²Th activity concentrations and TFs of tobacco components had a significant positive correlation. Based on the activity concentrations of the tobacco leaves, the annual inhalation effective dose to the lungs for an adult smoker was 0.32-0.81 mSv y^-1 (average 0.60 mSv y^-1). The Excess Lifetime Cancer Risk (ELCR) caused by smoking was an average of 2.39 × 10^-3.

Radioactivity concentration and transfer factors of natural radionuclides 226Ra, 232Th, and 40K from peat soil to vegetables in Selangor, Malaysia

The activity concentrations of naturally occurring radionuclides in vegetables and peat soil were investigated to determine the transfer factors of radionuclides from soil to vegetables obtained from farms in Klang Selangor. The results showed that the activity concentration ranges for 226Ra, 232Th, and 40K in the soil of the vegetable were 2.72-46.54 Bqkg-1, 9.01-54.84 Bqkg-1, and 19.22-477.76 Bqkg-1, respectively. The activity concentration ranges for 226Ra, 232Th, and 40K in various vegetable samples were 0.41-3.41 Bqkg-1, 0.02-3.56 Bqkg-1, and 16.22-317.49 Bqkg-1, respectively. The transfer factors from soil-to-plant for 226Ra, 232Th, and 40K were in the ranges of 0.01-0.67, 0.00-0.17, and 0.26-2.52, respectively. Radionuclide 40K has the highest transfer factor value in most vegetables, especially in the fruit type vegetable, and 232Th was found to have the lowest transfer factor value in all vegetables. The acquired results were compared to the levels that are globally recognized as acceptable. The transfer factor value of 40K was greater than 1 found in beans and fruit type vegetables, showing a similar value in other studies involving tropical plants, while transfer factor value for 226Ra was 15 times higher than the value reported in the data for tropical plants.