Activity concentrations of238U and226Ra in agricultural samples

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.

Transfer factors for natural radioactivity into date palm pits

Palm pits are used in various human and animal feed products. In this study, the natural radioactivity levels from soil and date palm pits of 9 samples collected from major date palm farms in three different regions (Buraidah, Al-Zulfi and Al-Majmaah) of Saudi Arabia were determined by using the high purity germanium (HPGe) gamma-ray spectrometer. The mean activity concentrations of ²²⁶Ra, ²³²Th, ¹³⁷Cs and ⁴⁰K in soil samples were 12.8 ± 2.2, 10.2 ± 2.1, 0.28 ± 0.10 and 329 ± 87 Bg kg^-1, respectively. Similarly the mean activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in date palm pits were 5.6 ± 1.2, 2.8 ± 0.4 and 181 ± 17 Bq kg^-1, respectively, whereas ¹³⁷Cs could not be detected. The geometric mean of TF values (geometric standard deviation in parentheses) of ²²⁶Ra, ²³²Th, and ⁴⁰K were 0.33 (2.1), 0.22 (1.8) and 0.51 (2.0), respectively.

Uptake of radionuclides and stable elements from paddy soil to rice: a review

The critical paths for radionuclides and the critical foods in Asian countries differ from those in Western countries because agricultural products and diets are different. Consequently, safety assessments for Asian countries must consider rice as a critical food. As most rice is produced under flooded conditions, the uptake of radionuclides by rice is affected by soil conditions. In this report, we summarize radionuclide and stable element soil-to-plant transfer factors (TFs) for rice. Field observation results for fallout (137)Cs and stable Cs TFs indicated that while fallout (137)Cs had higher TF than stable Cs over several decades, the GM (geometric mean) values were similar with the GM of TF value for (137)Cs being 3.6 x 10(-3) and that for stable Cs being 2.5 x 10(-3). Although there are some limitations to the use of TF for stable elements under some circumstances, these values can be used to evaluate long-term transfer of long-lived radionuclides in the environment. The compiled data showed that TF values were higher in brown rice than in white rice because distribution patterns for elements were different in the bran and white parts of rice grains.

Uptake and distribution of natural radioactivity in wheat plants from soil

The uptake of naturally occurring uranium, thorium, radium and potassium by wheat plant from two morphologically different soils of India was studied under natural field conditions. The soil to wheat grain transfer factors (TF) were calculated and observed to be in the range of 4.0 x 10(-4) to 2.1 x 10(-3) for 238U, 6.0 x 10(-3) to 2.4 x 10(-2) for 232Th, 9.0 x 10(-3) to 1.6 x 10(-2) for 226Ra and 0.14-3.1 for 40K. Observed ratios (OR) of radionuclides with respect to calcium have been calculated to explain nearly comparable TF values in spite of differences in soil concentration of the different fields. They also give an idea about the discrimination exhibited by the plant in uptake of essential and nonessential elements. The availability of calcium and potassium in soil for uptake affects the uranium, thorium and radium content of the plant. The other soil factors such as illite clays of alluvial soil which trap potassium in its crystal lattice and phosphates which form insoluble compounds with thorium are seen to reduce their availability to plants. A major percentage (54-75%) of total 238U, 232Th and 226Ra activity in the plant is concentrated in the roots and only about 1-2% was distributed in the grains, whereas about 57% of 40K activity accumulated in the shoots and 16% in the grains. The intake of radionuclides by consumption of wheat grains from the fields studied contributes a small fraction to the total annual ingestion dose received by man due to naturally existing radioactivity in the environment.