A study of Cs-137 spatial distribution in soil thin sections by digital autoradiography (original) (raw)
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Journal of Geochemical Exploration, 2014
Digital autoradiography with imaging plates and microprobe analysis was used to study 137 Cs micro-distribution in thin sections of the podzolic sandy soil typical for the Chernobyl remote impact zone 25 years after the accident. The zone is notable for contamination of the so-called condensation type where the contribution of the "hot" fuel particles was comparatively low. The initial 137 Cs contamination level of the study plot located on the Iput river terrace ca. 20 km to the east of the town of Novozybkov, Bryansk region, was approx. 40 Ci/km 2 . According to the modern soil core data the main portion of cesium radioisotopes is still concentrated in the 10-20 cm thick surface layer. Thin sections were prepared from the top 0-10 cm layer of the soil profile located on the shoulder of the relatively steep northern slope of the forested hill. Autoradiography of the thin sections has clearly shown both cluster and dispersed patterns of 137 Cs distribution presumably reflecting initial radiocesium accumulation in the surficial organic layer with mineral admixture and subsequent lateral and vertical propagation due to water movement and filtration. The propagation was accompanied by fixation of 137 Cs ions on surfaces of soil particles. High sensitivity (0.03 Bq/cm 2 ) and resolution (ca 40 μm) of the applied technique enable us to reveal concentration and dispersion zones in soil thin sections on microscale level. Soil micromorphology and microprobe analysis have shown to be helpful in deciphering soil chemical and mineral composition assumed to be responsible for 137 Cs retention in the soil top layer.
Vertical Distribution of Cs-137 in Soils of Orel Region 30 Years after Chernobyl Accident
IOP Conference Series: Materials Science and Engineering, 2020
The article presents the first results of the study of vertical redistribution of Radiocaesium in different types of agricultural soils of the Orel region, performed in the period 2016-2017. Orel region, one of the 19 regions of Russia, where as a result of the Chernobyl accident (1986) large areas were contaminated with various radionuclides, including Cs-137, with soil contamination level Cs-137 above 1 Ki/km2 (37 kBq/m2). The work was carried out as a private initiative study within the field teaching and scientific practice of the Ecology Faculty of the Peoples’ Friendship University of Russia (RUDN). It was found that the main stock of Radiocaesium falls on the top 20 cm of arable soils. Despite the overall reduction in dose over 30 years, Radiocaesium is still traceable to a depth of 40-50 cm, depending on soil type, organic matter content, particle size distribution and other factors.
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.
Journal of Geochemical Exploration, 2011
Mapping of 137 Cs activity was performed to test the idea of a non-random (deterministic) character of distribution of chemical elements and their compounds in space. Spatial distribution of the particular chemical elements and their compounds is proposed to be treated as a continuous single whole numerical field with a specified structure where each value and its change are related to the others. Direct measurements of the Chernobyl 137 Cs activity and its mapping within the study plots confirmed the regular character of the radionuclide spatial structure on different scale levels. The observed spatial structure was suggested to reflect the secondary transformation of the initial fallout due to lateral and vertical migration of 137 Cs with water as the main agent of physical and chemical migration related both to meso-and micro-relief features. Proposed deterministic approach is believed to stimulate development of the non-stochastic mathematical and physical methods in the analysis and forecast of spatial structure of geochemical fields.
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.
Journal of Environmental Radioactivity, 2020
A detailed study of 137 Cs redistribution was conducted within a small agricultural catchment in the highly contaminated Plavsk radioactive hotspot in the Tula region of Central Russia, 32 years after the Chernobyl nuclear power plant (NPP) accident, which occurred on April 26, 1986. Although more than three decades have passed since the Chernobyl NPP incident, 137 Cs contamination is high. The 137 Cs inventory varies from 67 to 306 kBq⋅m − 2 , which is 2-6 times higher than the radiation safety standard; however, the soils remain suitable for crop cultivation. The initial 137 Cs fallout within the Plavsk radioactive hotspot was extremely heterogeneous, with a trend of decreasing 137 Cs inventories from the NW to the SE directions within the studied territory. Contemporary 137 Cs inventories are also very heterogeneous in the studied catchment. However, the trend of the initial 137 Cs fallout does not appear in the contemporary 137 Cs inventories on the slopes. Two methods of interpolation (expert-visual and automatic) were used to calculate the 137 Cs budget, revealing high similarity in their 137 Cs loss estimates; however, a large discrepancy was observed in their 137 Cs gain estimates. A detailed analysis of 137 Cs redistribution revealed the importance of hollows and "plow ramparts" (positive topographic forms on the boundaries of cultivated fields) in the transport and deposition of sediments. A quarter of the total 137 Cs gain was deposited within the arable land, whereas a quarter was deposited within the non-plowing sides of the dry valley; the other half was deposited in the valley bottom. About 7-8 × 10 6 kBq of the 137 Cs inventory flowed out of the catchment area, which was only about 2% of the 137 Cs fallout after the Chernobyl NPP accident. About 89% of the total 137 Cs reserve is concentrated in the top (0-25 cm) layer of soils, regardless of land use or location within the catchment.
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.
Eurasian Soil Science, 2007
Pits of sandy alluvial soils were studied in different parts of the floodplains of the Iput River and its tributary the Buldynka River near the settlement of Starye Bobovichi (Bryansk oblast). The 137 Cs content in the soil horizons varied from 0.01 to 31.2 Bq/g reaching the maximum in the initially polluted layers buried at depths of 6 to 40 cm. Radiocesium was found in all the particle-size fractions with its predominate concentration in the finest fractions. The specific 137 Cs activity in the fractions of <1, 1-5, 5-10, and >10 µ m comprised 44.1 ± 11.5 ; 33.3 ± 7.6 , 20.9 ± 4.9 , and 2.4 ± 0.6 Bq/g of soil. However, the contribution of the coarse (>10 µ m) fractions to the total radiocesium pool in the soils (19-60%, or 34 ± 2% on the average) was comparable with that of the clay fraction (16-71%, or 38 ± 3% on the average), because of the predominance of the sand-size fractions in the soils. The highest coefficient of variation with respect to the relative contribution of particular fractions to the total soil pool of 137 Cs was characteristic of the fraction of 5-10 µ m; in the other fractions, it varied from 31 to 41%. The portion of 137 Cs bound with the finest fractions increased in the deeper layers. The total 137 Cs activity in the polluted horizons of the soils was mainly determined by its concentration in the clay fraction (Spearman's coefficient of rank correlation ( r ) for the moderately polluted horizons comprised 0.926 at n = 14). It was experimentally proved that clay particles, upon the destruction of organic films on their surface, could readsorb the released radiocesium for a second time.