Relationship between Mean Annual Precipitation and Inventories of Fallout Radionuclides (137Cs and 210Pbexcess) in Undisturbed Soils around the World: A Review (original) (raw)
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Variability of 137 Cs inventories in undisturbed surface soils
Derivation of 137Cs deposition density from measurements of 137Cs inventories in undisturbed soils, 2002
The 137Cs inventories in undisturbed soils were measured for 292 locations across the territory of Vietnam. The logarithmic inventory values were regressed against characteristics of sampling sites, such as geographical coordinates, annual rainfall and physico-chemical parameters of soil. The regression model containing latitude and annual rainfall as determinants could explain 76% of the variations in logarithmic inventory values across the territory. The model part was interpreted as the logarithmic 137Cs deposition density. At the 95% confidence level, 137Cs deposition density could be predicted by the model within ± 7% relative uncertainty. The latitude mean 137Cs deposition density increases northward from 237 Bq m–2 to 1097 Bq m–2, while the corresponding values derived from the UNSCEAR (1969) global pattern are 300 Bq m–2 and 600 Bq m–2. High 137Cs inputs were found in high-rainfall areas in northern and central parts of the territory. 2002 Published by Elsevier Science Ltd.
Journal of Environmental Radioactivity, 2013
Inventories and vertical distribution of 137 Cs were determined in La Plata region undisturbed soils, Argentina. A mean inventory value of 891 AE 220 Bq/m 2 was established, which is compatible with the values expected from atmospheric weapon tests fallout. The study was complemented with pH, organic carbon fraction, texture and mineralogical soil analyses. Putting together Southern Hemisphere 137 Cs inventory data, it is possible to correlate these data with the mean annual precipitations. The large differences in 137 Cs concentration profiles were attributed to soil properties, especially the clay content and the pH values. A convectionedispersion model with irreversible retention was used to fit the activity concentration profiles. The obtained effective diffusion coefficient and effective convection velocity parameters values were in the range from 0.2 cm 2 /y to 0.4 cm 2 /y and from 0.23 cm/y to 0.43 cm/y, respectively. These data are in agreement with values reported in literature. In general, with the growth of clay content in the soil, there was an increase in the transfer rate from free to bound state. Finally, the highest transfer rate from free to bound state was obtained for soil pH value equal to 8.
Vertical distributions of 137Cs in soils: a meta-analysis
Journal of Soils and Sediments, 2014
Purpose The vertical distribution of 137 Cs-an artificial fallout radionuclide-is controlled by soil characteristics and processes that may differ among soil groups. The application of a single modelling approach to large number of soil profiles provides an original contribution to the literature and allows for comparison between these different soil groups. Materials and methods In order to quantify 137 Cs migration in soils, we compiled and modelled depth-distributed data documented in the literature published before 2013. The resulting database comprised ninety-nine 137 Cs profiles sampled in 14 soil groups of the World Reference Base (WRB) classification (FAO 1998) under different land uses or covers and collected at various geographical locations in the Northern hemisphere between 1992 and 2007. Results and discussion The 137 Cs profiles were classified in seven different categories according to the shape and location of radiocaesium peak. Depth of the latter ranged between 0 and 12 cm (median of 2 cm) and maximal penetration of cesium reached from 12 to 60 cm. The 137 Cs depth distributions in these soils were fitted using a diffusion-convection equation to allow comparison between different soil groups.
Determination and analysis of distribution coefficients of 137Cs in soils from Biscay (Spain)
Environmental Pollution, 2000
The distribution coecient of 137 Cs has been determined in 58 soils from 12 sampling points from Biscay by treating 10 g with 25 ml of an aqueous solution with an activity of 1765 Bq in the radionuclide, by shaking during 64 h and measuring the residual activity with a suitable detector. Soils were characterised by sampling depth, particle size analysis and the usual chemical parameters. Soils were thereafter treated to ®x the chemical forms of 137 Cs speciation by successive extractions in order to determine fractions due to exchangeable, associated with carbonates, iron oxide and organic matter fractions, obtaining by dierence the amount taken by the rest of the soil constituents. For this research, 16 soils from four points were selected from the previous samples. The greatest mean percentages of 137 Cs sorption were with the rest (69.93), exchangeable (13.17) and organic matter (12.54%) fractions. This paper includes also the calculation of partial distribution coecients for chemical species as well as relations of distribution coecients both among them and with soil parameters.
Derivation of 137 Cs deposition density from measurements of 137 Cs inventories in undisturbed soils
The 137 Cs inventories in undisturbed soils were measured for 292 locations across the territory of Vietnam. The logarithmic inventory values were regressed against characteristics of sampling sites, such as geographical coordinates, annual rainfall and physico-chemical parameters of soil. The regression model containing latitude and annual rainfall as determinants could explain 76% of the variations in logarithmic inventory values across the territory. The model part was interpreted as the logarithmic 137 Cs deposition density. At the 95% confidence level, 137 Cs deposition density could be predicted by the model within ± 7% relative uncertainty. The latitude mean 137 Cs deposition density increases northward from 237 Bq m –2 to 1097 Bq m –2 , while the corresponding values derived from the UNSCEAR (1969) global pattern are 300 Bq m –2 and 600 Bq m –2. High 137 Cs inputs were found in high-rainfall areas in northern and central parts of the territory.
Retention of 10Be, 137Cs and 210Pbxs in soils: Impact of physico-chemical characteristics
Geoderma
The 10 Be, 137 Cs and 210 Pbxs radionuclide fallout has been used for the last several decades to quantify various soil and geomorphological processes and their rates, on different time scales. However, a basic assumption of the studies relying on these radionuclides is that they have a strong affinity for soil particles and that their mobility in soil solution and losses through leaching can be neglected. Another area of the scientific literature deals with the radionuclide mobility in soils as solute. In that context, the objective of this work is to determine the pedological conditions under which this hypothesis of poor solute mobility of radionuclides is valid. To this end, meteoric 10 Be, 137 Cs and 210 Pbxs concentrations were measured in six soil profiles representative of 5 soil types contrasted in terms of physico-chemical properties: an Andosol and a Luvisol under pasture, a Ferralsol and a Leptosol under forest and a Podzol both under forest and cultivation. The main soil properties (soil pH, organic carbon (OC) content, particle size distribution and specific extractions) were measured. The <2 µm fraction of the samples was extracted to measure radionuclide activities and undertake mineralogical analysis. Mass balance calculations were made to estimate the potential isotope losses from the soil profiles. Results show that meteoric 10 Be is significantly leached from soils whose pHw is lower than 5, regardless of the <2 µm particle proportion and Fe oxides content. Significant 137 Cs losses Podzols, Ferralsols and most probably other acidic tropical soil types (Nitisols, Acrisols, Plinthisols).
The purpose of this study is to understand and quantify the relationships between current 137 Cs inventories and the soil properties and the physiographic characteristics. A total of 36 cores were taken in seven transects with different slopes, lithology and land use. The analysis focused on the 137 Cs mass activity as well as inventories and its relationship with soil properties as grain size and organic matter. The mass activity of 137 Cs and the inventories varied between 3.6 and 63.7 Bq kg À1 and between 521.7 and 3304.4 Bq m À2 , respectively. At uncultivated soils, high concentrations of 137 Cs are located in the top 10 cm and decreased exponentially in depth. Cultivated soils record disturbed and heterogeneous 137 Cs profiles with values of mass activity and inventories up to 38.7 Bq kg À1 and 2510.8 Bq m À2 , respectively. The 137 Cs inventories were significantly higher in uncultivated soils (mean: 2086.9 Bq m À2) compared to cultivated soils (mean: 1397.1 Bq m À2). The 137 Cs mass activity showed a significant positive correlation with organic matter, silt and clay, but it was negatively correlated with sand and pH respectively. High levels of 137 Cs were found at altitudes between 500 m and 640 m a.s.l, and at slopes from 8 to 11 , as well as in dense scrub land and Fersialitic soils. A principal component analysis showed that more than 86.7% of the variance in 137 Cs mass activity was explained by the organic matter content and the land use. The results of this study provide insights into the effects of soil properties and physiographic factors on the behaviour of 137 Cs in soils of Mediterranean environments of North Africa and strengthen the reliability of this radioisotope as an erosion tracer.
Spatial 137 Cs distribution in forest soil
Nukleonika, 2006
This work presents the distribution of radioactive caesium in several types of forest soil originating from the Lesisko reserve (Opole Province, Poland). Vertical distribution of 137 Cs isotope was determined in the profiles related to physicochemical properties of different types of soils and their location. Thickness of emerging genetic horizons, structure and morphology of soil profiles were determined. The highest 137 Cs activities were found in Of and A horizons. At the same time, there was a sudden drop of 137 Cs activity in mineral horizons of soil profiles. By analysis of caesium radioisotope content and its distribution in soil profiles significant correlations were observed between certain physico- chemical properties (e.g. pH value, hydrolytic acidity, granulometric composition) of soils in selected forest habitats.
Vertical profile of 137Cs in soil
Applied Radiation and Isotopes, 2004
In this paper, a vertical distribution of 137 Cs in undisturbed soil was investigated experimentally and theoretically. Soil samples were taken from the surroundings of the city of Kragujevac in central Serbia during spring-summer of 2001. The sampling locations were chosen in such a way that the influence of soil characteristics on depth distribution of 137 Cs in soil could be investigated. Activity of 137 Cs in soil samples was measured using a HpGe detector and multichannel analyzer. Based on vertical distribution of 137 Cs in soil which was measured for each of 10 locations, the diffusion coefficient of 137 Cs in soil was determined. In the next half-century, 137 Cs will remain as the source of the exposure. Fifteen years after the Chernobyl accident, and more than 30 years after nuclear probes, the largest activity of 137 Cs is still within 10 cm of the upper layer of the soil. This result confirms that the penetration of 137 Cs in soil is a very slow process. Experimental results were compared with two different Green functions and no major differences were found between them. While both functions fit experimental data well in the upper layer of soil, the fitting is not so good in deeper layers. Although the curves obtained by these two functions are very close to each other, there are some differences in the values of parameters acquired by them.
Scientific Reports
the aims of this study were to investigate the vertical distributions of natural radionuclides 232 Th, 226 Ra and 40 K as well as anthropogenic radionuclide 137 cs in soil samples and to analyze the correlation among the radioactivity of these radionuclides and the physiochemical characteristics of soil samples namely pH, grain size, carbonate content and organic matter. Risk assessment of the radiological hazard has also been estimated. forty-four soil samples were collected from eleven locations in Qatar at four depth levels from 0 to 16 cm. The average concentrations of 232 Th, 226 Ra, 40 K and 137 cs in the soil depth of 16 cm were 10, 17, 201 and 4 Bq/kg, respectively, which were within the reported world mean. The external absorbed gamma dose rate, the annual effective dose, the mean radium equivalent activity, the external hazard index and the lifetime cancer risk were 22 nGy/h, 0.027 mSv/y, 47 Bq/ kg, 0.125 and 0.096 × 10 −3 , respectively. These values were far below the minimum recommended international values. The level of radioactivity concentrations in the soil was affected by the physiochemical characteristics of the soil. the positive correlation with highest R 2 value was found among the radioactivity concentrations of 232 th and 40 K and the soil clay content. total organic carbon was also positively correlated for 226 Ra and 137 Cs activity concentrations, whereas, carbonate content was negatively correlated with the radioactivity concentrations of 232 th and 40 K. As far as soil moisture content is concerned, the positive correlation with highest R 2 value was obtained for 226 Ra activity concentrations. Radioactivity has become an issue of major concern over the years due to its association with human health 1,2. Natural and artificial radioactive isotopes are host in the environment. Radionuclides, with different biogeochemical processes and important movability, can influence the environment through bioaccumulation and are hazardous for the environment and human health. The radioactive isotopes in the environment cause the external radiation dose to human organisms, while the isotopes integrated by inhalation and ingestion are the origin of the internal radiation dose. Studies about dose-effect relationships of radioactive materials have helped to increase knowledge about the risks associated with radiations and have played an important role in developing radiation protection regulations. Characteristic of soil is instantaneously concerned to the essence of life 3. The risk from Cs-137 varies with its diffusion rates in soil. If Cs-137 migrate slowly in soil, the internal irradiation will be higher due to higher absorption by plants roots especially from the top surface of 5 cm depth. However, if Cs-137 diffuse rapidly, the external radiation will be less as in this case, the uppermost soil surface acts as a shield against radioactivity found in deeper soil layers 4. Therefore, assessment of the diffusion of natural and artificial radionuclides in soil is important to protect human and environment 5. Naturally Occurring Radioactive Materials (NORM) refers to the natural origins of radiations i.e. from naturally occurring radioisotopes 6. Natural radioactivity can result from cosmogenic radioactive isotopes which are continuously produced by the effect of cosmic radiation (e.g.