Mass Activity Concentration Research Articles

Transfer factors of natural radionuclides and 137Cs from soil to plants used in traditional medicine in central Serbia

Transfer factors of natural radionuclides and 137Cs from soil to plants used in traditional medicine were determined. The transfer factors (TF) were calculated as Bq kg−1 of dry plant per Bq kg−1 of dry soil. Mass activity concentrations of 226Ra, 232Th, 40K and 137Cs in soil and plant samples were measured with high purity germanium detector (HPGe). The concentrations of As, Co, Cr, Cu, Mn, Ni, Pb and Zn were determined, as well as the cation exchange capacity (CEC) and the content of exchangeable cations (Ca, Mg, K, Na). Wide ranges of values were obtained for all the metals, especially for Cr and Ni.The Absalom model was used for determination of the amount of 137Cs transferred from soil to plant based on soil characteristics such as pH, exchangeable potassium, humus and clay contents. The estimated transfer factors were in the range from 0.011 to 0.307 with an arithmetic mean of 0.071, median of 0.050, geometric mean of 0.053 and geometric standard deviation (GSD) of 2.08. This value agreed well with that calculated from the measurements of 0.069, geometric mean 0.040 and GSD 3.19. Correlations between radionuclides, metals, physicochemical properties and transfer factors were determined by Spearman correlation coefficient. There was a strong positive correlation between 137Cs transfer factor and the ratio of transfer factor for K and 137Cs. Principal Component Analysis (PCA) was performed in order to identify some pattern of data.

Optimising in situ gamma measurements to identify the presence of radioactive particles in land areas

High-coverage in situ surveys with gamma detectors are the best means of identifying small hotspots of activity, such as radioactive particles, in land areas. Scanning surveys can produce rapid results, but the probabilities of obtaining false positive or false negative errors are often unknown, and they may not satisfy other criteria such as estimation of mass activity concentrations. An alternative is to use portable gamma-detectors that are set up at a series of locations in a systematic sampling pattern, where any positive measurements are subsequently followed up in order to determine the exact location, extent and nature of the target source. The preliminary survey is typically designed using settings of detector height, measurement spacing and counting time that are based on convenience, rather than using settings that have been calculated to meet requirements. This paper introduces the basis of a repeatable method of setting these parameters at the outset of a survey, for pre-defined probabilities of false positive and false negative errors in locating spatially small radioactive particles in land areas. It is shown that an un-collimated detector is more effective than a collimated detector that might typically be used in the field.

Assessing radiation exposure of herbaceous plant species at the East-Ural Radioactive Trace

The East-Ural Radioactive Trace (EURT) is a result of the Mayak Production Association accident that occurred in 1957 in Russia. Radiological assessment improves the interpretation of biological effects of exposure to ionizing radiation. Therefore a modeling approach was used to estimate dose rates on Leonurus quinquelobatus, Silene latifolia, Stellaria graminea and Bromus inermis. Soil-to-organism transfer parameter values are delivered from empirical data of 90Sr and 137Cs soil and vegetative plant mass activity concentrations. External and internal whole-body dose rates were calculated using deterministic (The ERICA Tool-Tier 2 and R&D 128/SP1a) and probabilistic (The ERICA Tool-Tier 3) methods. The total dose rate for herbs was under 100 μGy h−1 at the most polluted site. The total absorbed dose rates increased 43–110 times (Tier 3) for different herbaceous plant species along the pollution gradient. Based on these data, it can be concluded that herbaceous plant populations currently exist under low-level chronic exposure at the EURT area.

Beryllium-7 activity concentration in maize during the growth period

Beryllium-7 (7Be) activity in maize was measured in Yangling County, Shaanxi Province, on the Loess Plateau Region of China in 2007. The 7Be mass activity concentration in maize leaf samples was significantly greater than in maize stem, maize root and maize grain samples. The 7Be activity in maize leaves accounted for 78% of the total maize 7Be activity. The 7Be mass activity concentration in maize varied from 25.4 to 122.4 Bq kg−1 and areal activity concentration held by maize from 1.2 to 111.5 Bq m−2 during the growth period. The percentage of 7Be areal activity concentration held by maize relative to the 7Be areal activity concentration measured in reference soils ranged from 0.4 to 24.2% with a mean of 13.7%.

Beryllium-7 activity concentration in plants on the Loess Plateau, China

The activity concentration of beryllium-7 (7Be), a naturally occurring cosmogenic radionuclide produced in the upper atmosphere, was measured in plants on the Loess plateau of China during the growing season of 2005. The 7Be mass activity concentration on July 27 ranged from 34.8 to 147.1 Bq kg−1 in herbaceous plants, from 47.6 to 116.1 Bq kg−1 in subshrubs, and from 15.7 to 56.8 Bq kg−1 in crop plants. The 7Be mass and areal activity concentrations of a mixture of herbaceous plants increased from 66.8 to 288.7 Bq kg−1 and from 0.7 to 46.5 Bq m−2, respectively, during the growing season. On an areal basis, the fraction of 7Be in plants in the soil–plant system increased from 0.4 to 8.4% during the growing season. Positive linear correlations were found between the increases of 7Be mass and areal activity concentrations in the inter-sampling intervals and the amount of precipitation.

Determination of the soil-to-grass transfer of 137Cs and its relation to several soil properties at various locations in Serbia

Transfer coefficients of 137Cs from soil to grass were determined for the terrain around the city of Kragujevac in central Serbia. Mass activity concentrations of 137Cs in soil and grass samples were determined with a high-purity Ge-detector (HPGe). The activity concentration at the depth of 20 cm was found to be in the range of 14.92–124.05 Bq kg−1, whereas the activity in grass for the same location was in the range of 4.60–84.95 Bq kg−1. Transfer factors (TFs) were in the range of 0.07 up to 1.94. Dependences of TFs on different soil characteristics were presented graphically. Weak dependences were determined between them. Absalom's model was used to predict TFs based on soil characteristics: pH value, contents of clay, exchangeable potassium and humus. A comparison of measured and predicted values from Absalom's model is shown graphically. It has been found that Absalom's model might be carefully used for the prediction of 137Cs in grass for specific regions.